Fighting Colorado potato beetle with RNA interference — ScienceDaily
Fighting Colorado potato beetle with RNA interference
- 1 Fighting Colorado potato beetle with RNA interference
- 2 Colorado Potato Beetles Are Hard to Control
- 3 6 Companion Plants To Battle Those Dreaded Potato Bugs
- 4 Colorado beetles flew to the potato. Methods of dealing with the Colorado potato beetle
- 5 Where did the Colorado potato beetle come from?
- 6 What does the pest beetle feed on?
- 7 How to beat the Colorado potato beetle?
- 8 How harmful is the Colorado beetle?
- 9 Colorado Potato Beetle
- 10 Related terms:
- 11 Insect Pests in Potato
- 12 Developments in Transgenic Biology and the Genetic Engineering of Useful Traits
- 13 Insects, nematodes, and other pests
- 14 Neurophysiological Effects of Insecticides
- 15 Structure, Evolutionary Conservation, and Functions of Angiotensin- and Endothelin-Converting Enzymes
- 16 Genetics of Resistance to Pests and Disease
- 17 GENETICALLY MODIFIED FOODS
- 18 Natural and Engineered Resistance to Plant Viruses, Part I
- 19 Chemical Ecology
Colorado potato beetles are a dreaded pest of potatoes all over the world. Since they do not have natural enemies in most potato producing regions, farmers try to control them with pesticides. However, this strategy is often ineffective because the pest has developed resistances against nearly all insecticides. Now, scientists from the Max Planck Institutes of Molecular Plant Physiology in Potsdam-Golm and Chemical Ecology in Jena have shown that potato plants can be protected from herbivory using RNA interference (RNAi). They genetically modified plants to enable their chloroplasts to accumulate double-stranded RNAs (dsRNAs) targeted against essential beetle genes. (Science, February 2015).
RNA interference (RNAi) is a type of gene regulation that naturally occurs in eukaryotes. In plants, fungi and insects it also is used for protection against certain viruses. During infection, many viral pathogens transfer their genetic information into the host cells as double-stranded RNA (dsRNA). Replication of viral RNA leads to high amounts of dsRNA which is recognized by the host’s RNAi system and chopped up into smaller RNA fragments, called siRNAs (small interfering RNAs). The cell then uses siRNAs to detect and destroy the foreign RNA.
But the RNAi mechanism can also be exploited to knock down any desired gene, by tailoring dsRNA to target the gene’s messenger RNA (mRNA). When the targeted mRNA is destroyed, synthesis of the encoded protein will be diminished or blocked completely. Targeting an essential gene of a crop pest can turn dsRNA into a precise and potent insecticide.
Some crop plants have recently been engineered by modifying their nuclear genomes to produce dsRNA against certain insects. «This never resulted in full protection from herbivory,» says Ralph Bock of the Max Planck Institute of Molecular Plant Physiology, «because the plant’s own RNAi system prevents the accumulation of sufficient amounts of dsRNA. We wanted to circumvent this problem by producing dsRNA in the chloroplasts instead.» These organelles, which perform photosynthesis in green plants, are descendants of formerly free-living cyanobacteria, which are prokaryotes that lack an RNAi system. Presuming that chloroplasts would accumulate high amounts of dsRNA, the scientists in Ralph Bock’s group decided to generate so-called transplastomic plants. In such plants, the chloroplast genome is the target of genetic modification instead of the nuclear genome.
To test this system on a real insect pest, the scientists chose the Colorado potato beetle. This little striped beetle was introduced into Europe accidentally at the end of the 19th century. Nowadays, it is a worldwide pest and can cause massive damage in agriculture. Besides potato leaves the adult beetle and its larvae also feed on other nightshade crops, like tomato, bell pepper and tobacco. The pest is difficult to control because of the widespread occurrence of insecticide resistance. «By using chloroplast transformation we generated potato plants that accumulate high amounts of long stable dsRNAs targeting essential genes in the beetle,» says Ralph Bock.
The efficacy of the dsRNAs as an insecticide was tested at the Max Planck Institute for Chemical Ecology in Jena. Larvae were fed on detached potato leaves and the mortality was monitored for nine days. The leaves were taken from transplastomic dsRNA plants, conventional transgenic dsRNA plants with a modified nuclear genome, and unmodified plants. For comparison, dsRNAs targeting two different genes were tested. «Transplastomic leaves producing dsRNA against the actin gene caused a mortality rate of 100% after five days of feeding,» says Sher Afzal Khan from Jena. The actin gene encodes a structural protein that is essential for cell integrity. In contrast, plants with a modified nuclear genome expressed much less dsRNA and only slightly slowed down the beetles’ growth.
These recent results show that changing the target of transformation from the nuclear genome to the chloroplast genome overcomes the major hurdle towards exploiting RNAi for crop protection. As many insect pests increasingly develop resistances against chemical pesticides and Bt toxins, RNAi represents a promising strategy for pest control. This technology allows for precise protection without chemicals and without production of foreign proteins in the plant.
Colorado Potato Beetles Are Hard to Control
Recent phone calls indicate home gardeners are being frustrated (again!) by the Colorado potato beetle. See the photos below. For more on this native insect-turned-pest, see Horticulture and Home Pest News, June 4, 2008.
The list of insecticides for homeowners is not much different now than it was two years ago. The first-choice products are the synthetic pyrethroids such as permethrin, cyfluthrin and esfenvalerate. Look for products labeled for use on potatoes in the home garden and apply according to label directions, including spray early, spray often.
Repeated and intensive use of insecticides against the Colorado potato beetle has lead to resistant to nearly all insecticides, including the common garden insecticide Sevin (carbaryl) in many areas. Alternate chemical classes to delay resistance development. Spray insecticide from one class during May and June for the first generation and then switch a different class during July and August for the second generation. Remember that the biorationals such as spinosad are only effective against very young larvae; they will not kill large larvae or adults.
Colorado potato beetle (adult).
Colorado Potato Beelte Larva.
6 Companion Plants To Battle Those Dreaded Potato Bugs
These pests (Colorado Potato Beetle) are a well known predator that target potatoes, tomatoes, eggplants and even our prized petunias! They not only thrive on the leaves, but are also known to feast on the fruit. If left unchecked, they will affect your garden’s yield and can kill young, tender seedlings.
You can get a step ahead of the beetles by growing certain plants that repel them (in ideal locations). I’ve listed a few recommendations below along with a section of tips that include recipes for a DIY spray which can be used to help keep these pesky fellows at bay.
There are other insects commonly confused with or misnamed as them, I added those at the bottom with reference links for more information.
How To Spot An Infestation: If you notice leaves with holes or other damage, check underneath. There will be a yellow cluster of eggs or larvae with orange and black. Simply remove the infested part and destroy.
A good resource for pictures of the life cycle along with additional details about this pest can be found here: University of Tennessee (pdf).
These are recommended as being suitable for repelling the beetles, intercrop between potatoes or in the space between rows.
- Bush Beans
- Catnip: Grow these in pots because it can be invasive…downside is that once the neighborhood cats figure out you’ve got the good stuff, you’ll be herding cats (danger diminished in more remote areas rather than city or towns).
- Cilantro (Coriander)
How To Get Rid Of Them
Manual control: Spot check leaves and shake off any that you see (or hand pick each one off but make sure to wear gloves), dispose of immediately by crushing their bodies.
Did you know: Ladybugs consider the larvae a tasty treat, consider growing items in the garden that will attract them so you have a thriving ladybug population (some ideas: Marigolds, Tansy, Fennel and Dill).
Diatomaceous Earth: This is a non-toxic method of pest control, simply dust the plant and surrounding soil with the powder and repeat after each rainfall.
Keep In Mind: The larvae will go underground to pupate and then emerge as adults after 10 days or so, you’ll need to be diligent and continue removal methods until all of these have been dealt with.
Homemade Repellent Teas or Infusions
Here are two different recipes you can try, once they’ve cooled pour into spray bottles and apply as needed (for best results spritz fresh applications after each rain).
- Tansy or Marigold Infusion: Fill a pot with freshly picked tansy (or marigolds), cover with water and bring to a boil. Reduce to simmer and cook until liquid has been halved. Strain, cool and use as needed.
- Wild Mustard Tea: Steep 4 whole cloves, a handful of wild mustard leaves, a clove of garlic in 1 cup of boiling water for 10 minutes. Remove from heat and cool, then use as spray. Source: Jerry Baker’s Bug Off!: 2,193 Super Secrets for Battling Bad Bugs, Outfoxing Crafty Critters, Evicting Voracious Varmints and Much More!
Here are a couple other insects that are commonly mistaken as potato bugs (with resources to check out):
- Pill Bugs (pillbugs), Roly Polys or Rolly Polly (because they roll up into a ball when aggravated). These guys are attracted to dead vegetation (though they will munch away on healthy, young stuff too). You can try enticing the critters away from the garden by setting out corn cobs and then dispose of them once they gather on the cob. You can find further info on this page (Wikipedia).
- Jerusalem Crickets: Yuck, so ugly! They feed on dead plant matter, you can learn more at (Wikipedia).
Colorado beetles flew to the potato. Methods of dealing with the Colorado potato beetle
With the beginning of spring, summer residents begin a period of intensive work. And first of all, gardeners have a “headache” — insect pests and the fight against them.
There are a large variety of insects on the planet, the “task” of which is to harm humans.
One of the most widespread and most unloved types of pests is the Colorado potato beetle. Thanks to their efforts, the plot of any gardener is devastated.
The Colorado potato beetle (Leptinotarsa decemlineata) is perhaps the most active insect species that eats potato leaves and more.
One of the most dangerous pests in the garden is the insect bear.
Strawberry agrofibre is a new method of growing berries. Read here.
Growing strawberries in the greenhouse in winter: //rusfermer.net/ogorod/plodovye-ovoshhi/vyrashhivanie-v-teplitsah/kak-vyrashhivat-klubniku-v-teplitse.html
Where did the Colorado potato beetle come from?
Let’s consider meeting a person with this pest. The history of the Colorado potato beetle originates from its appearance in potato fields in the middle of the 19th century in the eastern part of the USA.
In 1859, crop damage by these pests was first noticed in the state of Colorado. It was from that place that the long journey of the Colorado potato beetle began to other countries of the world.
Europe was intensively cultivating potatoes and the appearance of harmful insects, such as the Colorado potato beetle, was just a matter of time. On our open spaces the beetle appeared for the first time in 1949.
But let’s dwell on the conquest by the pest of a new continent and see which type of beetle is this pest. The length of the Colorado potato beetle ranges from 9 to 12mm, it reaches a width of up to 6-7mm and has a strongly convex body. The short oval-shaped beetle has a reddish-yellow color; there are black stripes over each elytra (5 pieces each). Colorado beetles can easily fly, as they have webbed wings.
The life of the Colorado potato beetle was devoted to years of fruitful study. After a long hibernation in the spring, they begin to go out and immediately “choose a house for themselves” on potato seedlings, and there they mate. Each hearth belongs to just one female. An interesting fact is that the beetle can generate on irrigated land
Central Asia up to 4 times! And we have only one generation develops. The Colorado potato beetle lives on average one year, but there are exceptions and its life span varies up to 2-3 years.
An interesting feature of the pest beetle is the variety of its resting forms. While common insects have only one form, the Colorado potato beetle has six of them:
- winter diapause;
- winter oligopause;
- summer dream;
- long summer diapause;
- repeated diapause;
- superpause (perennial diapause).
It makes no sense to describe each of the diapauses, because it already becomes clear that such plasticity of the beetle allows it to overcome various life adversities.
But only here the farmer suffers from this in the first place, because the fight against the pest becomes extremely difficult.
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What does the pest beetle feed on?
Colorado beetles are pests of plants of the nightshade family. Their favorite dish, as you know, is potatoes. Only on this, his taste preferences do not end, and he eats with great joy other decorative, medicinal or weedy nightshade: belladonna, prickly and bittersweet nightshade, and even dope with bleached they do not disdain!
Beetles are so adept in the search for a new food, that already some of them are switching to tomatoes, even in some places they are switching to bodyak, cabbage, mustard .
He eats plants that are unaccustomed to his diet, the beetle is not due to the fact that he is excessively hungry, but only because he needs moisture. They do not even eat the leaves completely, just nibble at the edges.
For a century and a half, the Colorado potato beetle has given preference to the solanaceae, which promises that it will not be soon addicted to other cultures.
Although other cultures are not affected by insects, it does not interfere with carefully processing the concentrated breeding areas of beetles.
How to beat the Colorado potato beetle?
Beetle, in addition to having the ability to physically survive for a long time, is able to withstand a long starvation. Thereby presenting for farmers the difficulty in the fight.
However, experienced gardeners use a large assortment of anti-pest agents, such as plant extracts or water decoctions. They tend to scare or destroy insects.
Separate reception of the Colorado potato beetle almost did not win. According to experts, it is necessary to apply a set of activities.
If the number of beetles is not critically large, then it will be enough to collect them with your hands, not forgetting to remove their larvae. Food bait is also suitable for catching these pests.
In addition to popular methods to rid the vegetation of the Colorado potato beetle, it is necessary to remember about the correctness of crop rotation, digging the soil in spring and autumn. It is also necessary to clean the tops in time, so that the beetles do not have where to winter. Amateur gardeners often plant garlic, beans, calendula, and beans near potatoes.
But among the many ways of pest control, the most necessary and effective is the treatment of plants with chemicals. Experienced farmers and gardeners lovers recommend the use of «Prestige» — as one of the best means to combat the Colorado potato beetle.
«Prestige» is used not only in the fight against the beetle, but also to protect plants from disease. You need to know that they can process only those potatoes that will be harvested in August. Only then will the poison have time to neutralize, because for complete elimination of chemistry it will be enough for 60 days.
That is why potatoes are recommended to be planted in the second half of April in order to start applying Prestige with confident calm.
The drug has an anti-stress effect, which makes the plant more resistant to abiotic and biotic effects of the environment. The component component imidacloprid (140g / l) has contact and systemic effects.
The advantages of the «Prestige» are great, it is:
- high workability;
- anti-stress effect;
- improving the quality of the product itself;
- underestimated toxicity and others.
Each year, breeders bring new varieties of grapes.
Features of plum planting: //rusfermer.net/sad/plodoviy/posadka-sada/sadovaya-sliva-prosto-vkusno-neobhodimo-polezno.html
How harmful is the Colorado beetle?
Several factors can determine the harmfulness of the Colorado potato beetle. One of those is the preference of the beetle and the larvae of one or several plants, more often potatoes.
The fecundity of these oligophages (the kind that stretches to a specific food object) is extremely high. One female of this type can lay about 700 eggs (there is a true and unique fixed figure — 3382 eggs!). By the end of the season, there may be up to 30 million pests.
The Colorado potato beetle is a fairly dangerous pest that causes harm to the family of the nightshade, and not just the potato. The larvae of beetles and adults eat the leaves and bush of young seedlings completely.
Summing up, we can safely say that the Colorado potato beetle is the most basic potato pest! For those who are not lazy and grow it on the site, the beetle is an eternal problem.
And if you take the statistics, then there are a lot of people who know what the “summer season” is!
Remember that it is better to treat the plants in time in order to avoid damage to your crop!
Colorado Potato Beetle
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Insect Pests in Potato
Edward B. Radcliffe, Abdelaziz Lagnaoui, in Potato Biology and Biotechnology , 2007
Colorado potato beetle has been the object of numerous innovations in crop protection. The first success of the agricultural insecticide era was the use of Paris green, cuprous acetoarsenite, against Colorado potato beetle in midwestern United States in the 1860s. Many advances in insecticide application equipment were in response to this pest, including first hand-operated compression sprayers, first wheel-drawn sprayers, first traction-operated dusters, first engine-operated sprayer and first air-blast sprayer ( Gauthier et al., 1981 ). Potatoes were also one of the first crops to be treated by airplane.
Colorado potato beetle is legendary for its capacity to develop insecticide resistance ( Forgash, 1981 ). Colorado potato beetle has developed resistance to all major classes of synthetic insecticidal classes, including the neonicotinoid imidacloprid ( Zhao et al., 2000 ). Imidacloprid resistance is still localized in the United States, but the trend is of concern as worldwide neonicotinoids are the insecticide class most used on potato.
Recommended thresholds for application of insecticidal sprays to control Colorado potato beetle are often based either on beetle densities or on defoliation. For example, treatment has been recommended if beetle densities reach 0.5 adults, 4 small larvae (1st and 2nd instar) or 1.5 large larvae per stem ( Ferro, 1985 ), exceed 20 larvae per plant ( Martel et al., 1986 ) or if defoliation exceeds 10% ( Holliday and Parry, 1987 ). However, treatments at or shortly after egg hatching tend to give best control. Sprays applied later may not control large larvae that are much more tolerant of exposure. Also, if spray applications are delayed, some larvae may have already quit feeding or dropped to the ground to pupate.
With the introduction of the neonicotinoids, a common approach to Colorado potato beetle control has been to apply the insecticide in-furrow or as seed piece treatments. Treating only border rows or some proportion of rows within fields could make for more efficient use of at-planting treatments and conserve susceptibility in the population ( Dively et al., 1998 ).
Crop rotation can be effective in delaying establishment of Colorado potato beetle in new plantings ( Wright, 1984 ; Sexson and Wyman, 2005 ). Overwintered Colorado potato beetles need to regenerate their flight muscles and do not oviposit until they have fed on a nutritionally adequate host plant. Rotating a planting by as little as 200–400 m from last year’s location can delay colonization of the new planting by 1–2 weeks, generally resulting in lower population densities than in nonrotated fields and can save 1–2 sprays for first-generation larvae. Reducing the need for repeated insecticide applications has the indirect benefit of reducing selection for insecticide resistance. In some situations, field rotation will sufficiently delay emergence of most summer adults until day lengths are short enough to induce diapause.
Developments in Transgenic Biology and the Genetic Engineering of Useful Traits
126.96.36.199 Colorado potato beetle
Colorado potato beetle ( Leptinotarsa decemlineata Say) is a major pest in North America and elsewhere. The CPB is notorious for its ability to rapidly develop resistance to insecticides that are used repeatedly for control. Insecticides having the same class of chemical structure will often have the same mode of action. Consequently, resistance develops more rapidly to an insecticide when used repeatedly as the only control measure. Additionally, the repeated use of one class kills the susceptible beetles, leaving those that are resistant, i.e. selecting for the resistant population. Consequently, to delay or prevent resistance, a complicated and expensive crop protection strategy involving insecticide rotation is necessary. Transgenic resistance was developed with the introduction of a gene that encodes the Cry3A protein derived from the bacterium B. thuringiensis var. tenebrionis and expressed in potato using the constitutive 35S cauliflower mosaic virus (CaMV 35S) promoter. The strategy was so successful that such plants were the first GM potato varieties to be commercialized by Monsanto using the varieties Russet Burbank, Atlantic, Snowden and Superior in North America from 1995 to 2001 ( Duncan et al., 2002 ). Extensive testing of the Bt-protected crops had established their safety for humans, animals and the environment, but ( Section 30.2 ) the product was withdrawn in 2001 mainly for commercial rather than agronomic reasons.
MD PhDDavid Rifkind, MD MSGeraldine L. Freeman, in The Nobel Prize Winning Discoveries in Infectious Diseases , 2005
DDT is an organic halogen that acts by disrupting the function of the nervous system, and kills insects rapidly upon contact.
In 1939 the Swiss government tested DDT against the Colorado potato beetle , a crop blight of worldwide importance. In 1943, the US Department of Agriculture did the same. In 1944 it was used to abort an outbreak of louse-borne typhus (see Chapter 9 ) in Naples, Italy. Because DDT proved to be remarkably successful in these initial trials, it was quickly accepted and used worldwide. During the Second World War, DDT was initially employed as a mothproofing in clothing and then as an insecticidal dusting powder, both for military combatants and for displaced civilians. It was found to be effective against lice, the vector of typhus; fleas, the vector of plague; and mosquitoes, the vector of both malaria ( Chapter 23 ) and yellow fever ( Chapter 12 ). In addition to preventing infectious disease transmission, its use in agriculture markedly increased crop yields and food supplies.
Insects, nematodes, and other pests
Philip R. Watkins, . T.J.V. Higgins, in Plant Biotechnology and Agriculture , 2012
Discontinued Bt crops
There are Bt crops that have been discontinued for various reasons. A Bt potato that targeted the Colorado potato beetle ( Letinotarsa decemlineata) was produced in 1996. This beetle had developed resistance to many chemical pesticides, but remained susceptible to Bt spray containing Cry3A toxins. A released variety of potato expressing the cry3A gene was successful at controlling the insect ( Perlak et al., 1993 ). However, many buyers and processors were hesitant to buy the genetically modified potatoes because of perceived public resistance to biotechnology crops. The Bt potato was withdrawn from the market in 2001.
StarLink™ was a maize variety containing the cry9C gene. The Cry9C protein is more slowly digested in a simulated stomach than other Cry proteins, leading regulatory authorities to raise concerns about its potential allergenicity in humans; they approved the maize only for livestock feed. In 2000 it was reported that traces of StarLink™ maize were detected in taco shells destined for human consumption ( Kaufman, 2000 ). StarLink™ was withdrawn from registration and an extensive program to remove all traces of the variety from the food chain was initiated. At the time of withdrawal it made up less than 1% of the total maize area in the United States and no positive samples have been detected since 2004. Since the “contamination” was publicized, 28 people have claimed allergic reactions after eating maize products that may have contained StarLink™. After testing by the U.S. Food and Drug Administration and Centers for Disease Control and Prevention, it was concluded that there was no evidence that the reactions reported were consistent with an allergic response ( CDC, 2001 ).
As part of the normal product development cycle, other Bt crops have been withdrawn by developers as they are superseded by new and improved varieties. Knockout™ maize was phased out in 2003, partly because of its relatively higher risk to the monarch butterfly (see next section), but also because other Bt lines were more efficient. Another variety of Bt maize (Bt Xtra™) was removed from the market after company mergers. With the current development of stacked trait crops many of the first generation of single trait crops will or have been replaced. This is necessary to ensure that resistance to the pyramided insect resistance genes is delayed for as long as possible. The Cry1Ac expressing cotton will be completely replaced by Bollgard II, which expresses both the cry1Ac and cry2Ab genes.
Neurophysiological Effects of Insecticides
Fipronil is a phenylpyrazole compound and was developed as a useful insecticide in the mid-1990s. It is effective against some insects such as the Colorado potato beetle and certain cotton pests that have become resistant to the existing insecticides. Fipronil is much more toxic to insects than to mammals, another advantage it has as an insecticide.
Fipronil has been found to block insect GABA receptor (Rdl). Wild-type Rdl of Drosophila was suppressed by TBPS, 4-n-proply-4′-ethynylbicycloorthobenzoate (EBOB), picrotoxinin, and fipronil ( Buckingham et al., 1994a ; Millar et al., 1994 ). Insect GABA receptors are different from vertebrate GABAA receptors in that they are not blocked by bicuculline ( Benson, 1988 ; Buckingham et al., 1994a ; ffrench-Constant et al., 1993 ; Millar et al., 1994 ; Sattelle et al., 1988 ), and are not potentiated by benzodiazepines and barbiturates ( Millar et al., 1994 ). The insensitivity to bicuculline is reminiscent of the GABAC receptor of vertebrates ( Qian and Dowling, 1993 ; Woodward et al., 1993 ).
Dieldrin-resistant Drosophila melanogaster and D. simulans were also resistant to fipronil but to a much lesser extent, and the [ 3 H]EBOB binding to these resistant strains was less inhibited by fipronil compared to susceptible strains ( Cole et al., 1995 ). Mutant Drosophila Rdl (A302S) expressed in Xenopus oocytes was also less sensitive to fipronil than wild-type receptors ( Hosie et al., 1995 ). Fipronil and desulfinyl derivative were more potent in houseflies than in mice as toxicants and in competing with [ 3 H]EBOB binding ( Hainzl and Casida, 1996 ). LD50 values of fipronil were 0.13 mg/kg and 41 mg/kg for housefly and mouse, respectively, and receptor IC50 values were 6.3 nM and 1010 nM for housefly and mouse, respectively.
Fipronil block of GABAA receptors of rat DRG neurons has recently been analyzed in detail ( Ikeda et al., 1999 ). Fipronil suppressed the GABA-induced whole-cell currents reversibly with an IC50 of 1.66 ± 0.18 μM Preapplication of fipronil through the bath suppressed GABA-induced currents without channel activation. These results indicate that fipronil acts on the GABA receptors in the closed state. From co-application of fipronil and GABA, the IC50 value for the activated GABA receptor was estimated to be 1.12 ± 0.21 μM. The association rate and dissociation rate constants and the equilibrium dissociation constant of fipronil effect were estimated to be 673 ± 220 M −1 sec −1 , 0.018 ± 0.0035 sec −1 , and 27 μM for the resting GABA receptor, respectively, and 6600 ± 380 M −1 sec −1 , 0.11 ± 0.0054 sec −1 , and 17 μM for the activated GABA receptor, respectively. Thus, both the association and dissociation rate constants of fipronil for the activated GABA receptor are approximately ten times higher than those for the resting receptor, with a resultant lower Kd value for the activated receptor. Experiments with co-application of fipronil and picrotoxinin indicated that they did not compete for the same binding site. It is concluded that although fipronil binds to the GABAA receptor without activation, channel opening facilitates fipronil binding to and unbinding from the receptor.
Single-channel recording experiments using the GABAA receptor of rat DRG neurons have revealed that fipronil prolonged the closed time without much effect on open time and burst du ( Ikeda et al., 1999 ). Thus, fipronil reduces the frequency of channel opening, thereby suppressing the receptor activity.
Structure, Evolutionary Conservation, and Functions of Angiotensin- and Endothelin-Converting Enzymes
Nathalie Macours, . Roger Huybrechts, in International Review of Cytology , 2004
The discovery of ACE in testes of several insect species, including H. irritans exigua ( Wijffels et al., 1996 ), Lymantria dispar ( Loeb et al., 1998 ), N. bullata , the Colorado potato beetle Leptinotarsa decemlineata, and the locust L. migratoria ( Isaac et al., 1999; Schoofs et al., 1998 ), implies that the function of tACE may have been conserved during the course of evolution. In L. decemlineata, ACE was detected in the germ cells, more particularly in developing spermatids and mature spermatozoa, whereas in L. migratoria, ACE was found in peripheral somatic cell bodies of the apical compartment of the testicular follicles and not in the germ cells. In the haematophagus fly H. irritans, expression of testicular ACE is induced after a blood meal, indicating a specific role in the maturation of spermatozoa ( Wijffels et al., 1996 ).
The possible importance of testicular ACE in reproduction became apparent by the observation that male D. melanogaster transheterozygotes of two mutant Ance alleles were found to be sterile ( Tatei et al., 1995 ), with the infertility linked to the failure of the spermatocytes to develop into active mature spermatozoa. Spermatogenesis proceeds normally in the mutants up to the spermatid stage, but these spermatids do not succeed in differentiating into spermatozoa. This change is accompanied by nuclear scattering and an abnormal morphology of the spermatids. Together with the observed expression pattern of Ance, the enzyme is believed to be required for spermatid differentiation through the processing of a regulatory peptide synthesized within the developing cyst ( Hurst et al., 2003 ).
The involvement of ACE in the control of spermatogenesis was also demonstrated by studies of the effects of AII and bovine ACE on the ability of the testes of L. dispar to synthesize and release ecdysteroids in response to testis ecdysiotropin (TE). The effect of TE on the initiation and up-regulation of ecdysteroid synthesis could be imitated by both AII and bovine ACE, raising the possibility that ACE is involved in the production of an AII-like peptide that modulates ecdysteroid synthesis in the testes of insects ( Loeb et al., 1998 ).
In female adults of the mosquito A. stephensi, ACE activity increases by a factor 2.5 after a blood meal. It is not known where this induced ACE is synthesized, but it accumulates in developing ovaries and in mosquito eggs ( Ekbote et al., 1999 ). Adding ACE inhibitors (captopril and lisinopril) to the blood meal of the mosquito leads to a size reduction of the batch of eggs laid in a dose-dependent manner. The ACE inhibitors reduce fecundity by interfering with the transfer of the oocytes along the oviducts ( Ekbote et al., 2003a ).
In the reproductive tissue of the tomato moth Lacanobia aleracea, almost all of the ACE activity is concentrated in the accessory glands of the male and in the spermatheca and bursa copulatrix of the (virgin) female. These high activities may imply the importance of ACE for peptide metabolism in the male and female reproductive tract. Changes in the levels of ACE activity in the reproductive tissues of males and females during mating, point toward a transfer of ACE from male to female during time of copulation ( Ekbote et al., 2003b ). This male ACE donated in the spermatophore might form a hitherto unknown male component of an energy-producing metabolic pathway, as is seen in the serine endopeptidase-dependent proteolytic cascade in the spermatophore of B. mori ( Aigaki et al., 1987, 1988 ).
In the fleshfly N. bullata, feeding of captopril results in an increase of vitellogenin titers in the fly hemolymph. It has been suggested that this effect is mediated through the trypsin-modulating oostatic factor TMOF. As already discussed, Neb-TMOF is an in vitro substrate of insect ACE. However, if TMOF were to be inactivated by ACE, inhibition of ACE would lead to an increase of TMOF levels in the hemolymph, resulting in a reduced vitellogenin synthesis. Therefore, an activating effect of ACE on TMOF is postulated ( Vandingenen et al., 2001 ). The discovery of ACE interactive peptides in the ovaries of the fleshfly ( Vandingenen et al., 2002a ), and the discovery that these peptide substrates originate from yolk gene products, strengthen the idea that ACE is a regulator of vitellogenic and developmental processes ( Hens et al., 2002; Vandingenen et al., 2002b ).
These physiological observations, in combination with the discovery of ACE protein in the gonads of numerous insects, undoubtedly show that ACE is a vital enzyme in insect reproduction. The further elucidation of the full role of ACE in this process necessitates including the description of all endogenous substrates.
Genetics of Resistance to Pests and Disease
Ivan Simko, . David Spooner, in Potato Biology and Biotechnology , 2007
188.8.131.52 Exotic sources of disease and pest resistance
Reports of disease resistance in wild and cultivated relatives of potato are abundant ( Table 7.1 ). Some species are especially potent sources of resistance to a number of diseases and pests. Resistance to ring rot, potato cyst nematode, root knot nematode (Meloidogyne chitwoodi), potato virus X (PVX), and potato virus Y (PVY) has been reported in Solanum acaule ; resistance to Colorado potato beetle (CPB) ( Leptinotarsa decemlineata), green peach aphid (Myzus persicae), potato tuberworm (Phthorimaea operculella), late blight, and Verticillium wilt has been reported in Solanum berthaultii; resistance to silver scurf, CPB, four species of root knot nematode, late blight, PLRV, PVY, thrips (Thrips palmi), and both Verticillium wilt species has been reported in Solanum chacoense; resistance to root knot nematode, late blight, PVX, tobacco etch virus, and Verticillium wilt has been reported in Solanum commersonii; resistance to potato cyst nematode, late blight, PLRV, Verticillium wilt, and potato viruses M, X, and Y has been reported in Solanum sparsipilum; resistance to soft rot, silver scurf, late blight, cucumber mosaic virus (CMV), henbane mosaic virus, and PVY has been reported in S. stoloniferum; and resistance to soft rot, CPB, root knot nematode, and Verticillium wilt has been reported in Solanum tarijense. The outgroup Solanum palustre seems to be an especially rich source of virus resistance genes. It is important to note that there is tremendous diversity within wild species and even within accessions, so fine screening is necessary to identify individual clones with resistance genes. From a breeding standpoint, it is encouraging to note that several of the wild species that are rich in disease resistance genes (e.g. S. berthaultii, S. chacoense, S. sparsipilum, and S. tarijense) are also easily accessible through the simple ploidy manipulations outlined below.
Table 7.1 . Sources of potato disease and pest resistance.
|Pathogen/Pest||Source of resistance||Reference|
|Alfalfa mosaic virus (AMV)||Solanum palustre||( Valkonen et al., 1992b )|
|Andean potato latent virus||S. palustre||( Valkonen et al., 1992b )|
|Cucumber mosaic virus (CMV)||Solanum fernandezianum, Solanum stoloniferum||( Horvath, 1994 ; Valkonen et al., 1995 )|
|Henbane mosaic virus||S. stoloniferum||( Horvath and Wolf, 1991 )|
|Potato leaf roll virus (PLRV)||Solanum chacoense, S. fernandezianum, S. palustre, Solanum sparsipilum, Solanum spegazzinii||( Helgeson et al., 1986 ; Valkonen et al., 1992a ; Brown and Thomas, 1994 ; Ruiz de Galarreta et al., 1998 )|
|Potato virus A (PVA)||Solanum polyadenium||( Valkonen, 1997 )|
|Potato virus M (PVM)||S. palustre, S. sparsipilum||( Valkonen et al., 1992b ; Ruiz de Galarreta et al., 1998 )|
|Potato virus S (PVS)||S. palustre||( Valkonen et al., 1992b )|
|Potato virus V (PVV)||Solanum maglia||( Valkonen, 1997 )|
|Potato virus X (PVX)||Solanum acaule, Solanum commersonii, Solanum lesteri, Solanum marinasense, Solanum oplocense, S. palustre, S. sparsipilum||( Horvath et al., 1988 ; Tozzini et al., 1991 ; Valkonen et al., 1992b )|
|Potato virus Y (PVY)||S. acaule, Solanum achacachense, Solanum acroscopicum, Solanum ambosinum, Solanum arnezii, S. chacoense, Solanum doddsii, S. fernandezianum, Solanum megistacrolobum, S. palustre, S. polyadenium, Solanum polytrichon, S. sparsipilum, S. stoloniferum, Solanum sucrense, Solanum tarnii, Solanum trifidum||( Horvath and Wolf, 1991 ; Horvath et al., 1988 ; Valkonen et al., 1992a ; Singh et al., 1994 ; Bosze et al., 1996 ; Valkonen, 1997 ; Takacs et al., 1999a )|
|Potato-yellowing virus||S. palustre||( Valkonen et al., 1992b )|
|Tobacco etch virus||S. commersonii||( Valkonen, 1997 )|
|Clavibacter michiganensis||S. acaule, Solanum phureja, Solanum sanctae-rosae, Solanum stenotomum, Solanum verrucosum||( Kurowski and Manzer, 1992 ; Ishimaru et al., 1994 ; Kriel et al., 1995a )|
|Erwinia carotovora/Erwinia chrysanthemi||Solanum bukasovii, Solanum bulbocastanum, Solanum circaeifolium, Solanum demissum, S. marinasense, S. phureja, S. stoloniferum, S. tarijense||( Łojkowska and Kelman, 1989 ; Carputo et al., 1996 ; Chen et al., 2003 )|
|Streptomyces scabies||Solanum boliviense, S. bukasovii, Solanum canasense, Solanum multidissectum||( Hosaka et al., 2000 )|
|Fusarium sambucinum||S. boliviense, Solanum fendleri, Solanum gandarillasii, Solanum gourlayi, Solanum kurtzianum, Solanum microdontum, S. oplocense, S. sanctae-rosae, Solanum vidaurrei||( Lynch et al., 2003 )|
|Helminthosporium solani||Solanum albicans, S. chacoense, S. demissum, S. oplocense, Solanum oxycarpum, S. stoloniferum||( Rodriguez et al., 1995 )|
|Verticillium albo-atrum||S. chacoense||( Concibido et al., 1994 ; Lynch et al., 1997 )|
|Verticillium dahliae||Solanum berthaultii, S. chacoense, S. commersonii, S. phureja, Solanum raphanifolium, S. sparsipilum, S. tarijense||( Corsini et al., 1988 ; Concibido et al., 1994 ; Bastia et al., 2000 )|
|Phytophthora infestans||S. ambosinum, S. berthaultii, Solanum brachycarpum, S. bulbocastanum, Solanum cardiophyllum, S. chacoense, S. circaeifolium, S. commersonii, S. demissum, S. fendleri, Solanum guerreroense, Solanum iopetalum, S. megistacrolobum, S. microdontum, S. pinnatisectum, S. raphanifolium, S. sparsipilum, S. stoloniferum, S. sucrense, S. verrucosum||( Holley et al., 1987 ; Tooley, 1990 ; Ruiz de Galarreta et al., 1998 ; Micheletto et al., 1999 ; Douches et al., 2001 ; Perez et al., 2001 ; Chen et al., 2003 )|
|Globodera pallida||S. acaule, Solanum brevicaule, S. sparsipilum||( Jackson et al., 1988 )|
|Meloidogyne arenaria||S. chacoense||( Di Vito et al., 2003 )|
|Meloidogyne chitwoodi||S. acaule, Solanum andreanum, S. boliviense, S. bulbocastanum, S. fendleri, Solanum hougasii||( Brown et al., 1989 , 1991 , 1999 , 2004 ; Mojtahedi et al., 1995 )|
|Meloidogyne hapla||S. bulbocastanum, S. chacoense||( Brown et al., 1995 ; Di Vito et al., 2003 )|
|Meloidogyne incognita||S. chacoense||( Di Vito et al., 2003 )|
|Meloidogyne javanica||S. chacoense, S. commersonii, S. tarijense||( Di Vito et al., 2003 )|
|Empoasca fabae||S. berthaultii||( De Medeiros et al., 2004 )|
|Leptinotarsa decemlineata||S. berthaultii, S. chacoense, S. circaeifolium, Solanum jamesii, Solanum neocardenasii, Solanum okadae, S. oplocense, S. pinnatisectum, S. polyadenium, S. tarijense, S. trifidum||( Dimock et al., 1986 ; Groden and Casagrande, 1986 ; Sinden et al., 1986 ; Cantelo et al., 1987 ; Neal et al., 1989 ; Pelletier and Smilowitz, 1990 , 1991 ; Neal et al., 1991 ; Franca and Tingey, 1994 ; Franca et al., 1994 ; Bamberg et al., 1996 ; Sikinyi et al., 1997 ; Rangarajan et al., 2000 ; Pelletier and Tai, 2001 ; Pelletier et al., 2001 ; Chen et al., 2003 )|
|Myzus persicae||S. berthaultii, S. bukasovii, S. bulbocastanum, Solanum chiquidenum, Solanum chomatophilum, S. circaeifolium, Solanum etuberosum, S. trifidum||( Lapointe and Tingey, 1986 ; Radcliffe et al., 1988 )|
|Phthorimaea operculella||S. berthaultii||( Malakar and Tingey, 1999 )|
|Thrips palmi||S. chacoense||( Fernandez and Bernardo, 1999 )|
Potato accessions rated as resistant/highly resistant (or hypersensitive/immune for virus resistance) are included in the table. More information about accessions can be found on the United States Potato Genebank website ( http://www.ars-grin.gov/ars/MidWest/NR6/ ).
GENETICALLY MODIFIED FOODS
Plants as Production Factories
Plants provide an unmatched capacity to produce products with a maximum efficiency and a minimum of energy – thus, cost-effectively. Plants can be bioengineered to produce insecticidal proteins using just carbon dioxide, water, and nitrogen, thereby reducing the need for expensive and energy-intensive chemical insecticide manufacturing. The potato which has been developed to produce proteins that protect it from both the Colorado potato beetle and the potato leaf roll virus is an excellent example. The combination of these two traits enables potatoes to be grown without the application of chemical insecticides and will result in environmental and economic savings. Approximately 5 million pounds of chemical insecticides are used to control these pests annually in the USA, and 2.5 million pounds of waste are generated in the production process. Less than 5% of the applied insecticide actually reaches the pest. Using the plant to produce these pesticides is more energy-efficient and environmentally acceptable.
One of the most exciting applications of plant biotechnology is the ability to produce edible vaccines in plants. For example, transgenic potatoes containing the nontoxic binding subunit of the E. coli enterotoxin as well as transgenic potatoes which express the capsid protein of Norwalk virus have been produced. The expressed proteins function as oral immunogens in humans which, if effective, could immunize people against the diarrheal diseases caused by these organisms. Efforts are under way to introduce such vaccines into banana, which would be eaten raw and thus serve as an ideal source to deliver this technology to developing countries, where inexpensive vaccines are urgently needed.
Improving crop yields is essential to meeting the increased food demands of an ever-increasing world population. Improving crop protection from pests and increasing crop yields through herbicide tolerance are two strategies that will help meet this need. Biotechnological enhancements of crops can insure that these changes occur quickly enough to meet global food needs. At the same time, agricultural biotechnology has advantages for the environment in terms of reductions in soil erosion and tilling, and less agricultural chemical use and run-off. The first generation of crops developed via biotechnology provides these agronomic and environmental benefits. The next generation of products is expected to provide greater direct consumer benefits, such as enhanced food quality and nutritional value.
Natural and Engineered Resistance to Plant Viruses, Part I
C Other examples
Two virus-resistant potato lines were deregulated in 1998 and 2000 in the USA. After failed attempts to create a potato line resistant to Potato leafroll virus (PLRV) by coat protein gene expression, lines expressing a PLRV replicase gene were created, field tested, deregulated, and commercialized ( Kaniewski and Thomas, 2004 ). Later, this resistance was stacked with a synthetic Bt gene that conferred resistance to Colorado potato beetle . Another potato cultivar was developed by adding the coat protein gene of PVY. Although many growers in the Pacific Northwest, Midwest US and Canada were growing transgenic potato, and no resistance breakage was reported, nor any detrimental impact on the environmental or human health, virus-resistant potato were withdrawn from the market after the 2001 season due to the reluctance of several large processors and exporters to adopt these products ( Kaniewski and Thomas, 2004 ).
In the People’s Republic of China, tomato and sweet pepper resistant to CMV were released as well as papaya resistant to PRSV ( James, 2009 ; Stone, 2008 ) ( Table 1 ). Limited if any, information is available on their adoption rate.
Although not released yet, the plum cultivar ‘Honeysweet’ resistant to PPV is under consideration for deregulation in the USA. The US Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) has granted this cultivar deregulated status ( Bech, 2007 ) and the Food and Drug Administration (FDA) has deemed a pre-market review of the ‘Honeysweet’ unnecessary. Presently, the Environmental Protection Agency (EPA) is examining deregulation petitions for ‘Honeysweet.’ Another PRSV-resistant papaya has been deregulated by two of the three US biotechnology regulatory authorities. Line X17-2 differs from the previously deregulated Hawaiian papaya in that it expresses the CP gene of a Florida isolate of PRSV and is suitable for cultivation in Florida ( Davis, 2004 ). APHIS and the FDA have granted X17-2 deregulated status ( Anonymous, 2009 ; Shea, 2009 ). The realized economic benefits and minimal environmental hazards of the previously deregulated virus-resistant Hawaiian papaya figured prominently into APHIS’ favorable consideration ( Gregoire and Abel, 2008 ). The EPA will consider the plant pest risk of X17-2 after the developer submits a petition for deregulation.
Falko P. Drijfhout, E. David Morgan, in Comprehensive Natural Products II , 2010
Monoterpenes are widely distributed in plants, and certainly act to deter predators. The vapor of several monoterpenes are effective in deterring biting flies, but generally C-10 compounds are too volatile for practical use. Part of the research therefore is to find compounds that are suitably modified to make them more persistent and show strong feeding deterrence. Earlier work on monoterpenes has been reviewed. 2
The abundant natural compound linalool ( 3 ) is an attractant for the Colorado potato beetle (CPB), Leptinotarsa decemlineata. Two isomeric derivatives of linalool, (Z)-5-(1.5-dimethylhex-4-enyldiene)-dihydrofuran-2-one ( 4 ) and (E)-5-(1.5-dimethylhex-4-enyldiene)-dihydrofuran-2-one ( 5 ), were synthesized and were found to be moderate antifeedants against the CPB. A lactone derived from linalool strongly affected the properties of the original compound linalool, which is an attractant to the CPB. A similar effect is seen with the activity of either linalool ( 3 ) or 4-isobutyl-5-isopropyl-5-methyl-dihydrofuran-2-one ( 6 ) to aphids. Compared to linalool, the lactone reduced the total time the aphid spent on the leaf. 16
Carvone ( 7 ), abundantly present in many essential oils 23 and present in trace amounts in conifer plants (Pinaceae), has antifeedant properties against the pales weevil, Hylobius pales, 24 and the large pine weevil, H. abietis, 25 as well as lepidopteran species. 26 Although various studies have confirmed the antifeedant or repellent properties of carvone, long-term protection of seedlings in the field has not been successful, probably due to the high volatility of carvone. In order to address this problem, less volatile analogues of the compound were synthesized. Twelve carvone analogues were tested, both in microassays and in twig bioassays. Although several were very active in the microassay, the results did not always correlate with the twig bioassay. 21 Of the compounds with very low volatility, the sulfoxide 8 and 9-butyl-8-hydroxy-p-menth-6-en-2-one ( 9 ) had AFI values comparable to carvone (1.00 and 0.82, respectively) and ED50 values of 0.15 and 0.06%, respectively, less than that of carvone (ED50 = 2.6%). 21 The more volatile carvone-8-epoxide ( 10 ) induced 100% antifeeding activity at high doses (100 nmol cm −2 ), but had an ED50 value of 0.52%.