On May 29, 2006, the Ministry of Health, Labor and Welfare (MHLW) created a system which provided a list of positive agricultural chemicals found in foods. This system has been done to prohibit the distribution of foods that contain agricultural chemicals above certain allowable level if the maximum residue limits (MRLs) have not been established. The agricultural chemicals include pesticides, feed additives, and veterinary drugs. This system aims at prohibiting the distribution of foods that contain residues of agricultural chemicals above certain allowable level.
The Positive List allows 799 agricultural chemicals and provided guidelines for the use of those chemicals for products destined to Japan. Maximum Residue Limits (MRL) have been set for chemicals, and are usually expressed in parts per million. The MRL has been applied to pesticides, feed additives, and veterinary drugs that can remain in foods but are unlikely to pose adverse health effects when consumed.
Data are given to members on Positive List and MRL, including the Japanese inspection protocol, violation results, sampling levels, and issues to be aware of, have been summarized in a report done by MHLW.
Indeed, to implement the positive list, various measures were needed to secure the safety of agricultural products using pesticides. In other words, only the agricultural chemicals registered in Japan are manufactured, imported, sold and used. Pesticides that are not confirmed and registered by scientific evaluation for safety cannot be used.
Therefore, when applying for agricultural chemical registration, it is necessary to submit test results (animal test etc.) such as toxicity. (Pesticides that may remain in food crops) The tests are as follows:
● Acute toxicity test
● Examination to investigate the influence of toxicity over the medium to long-term
● Test to obtain information for coping with acute intoxication due to an accident at an occasion of spraying and accidental ingestion
● Information on the decomposition route of agricultural chemicals in the body of animals and plants and the structure of decomposition products etc. is grasped
● Examination of the influence in the environment
● Test on the persistence of agricultural crops
However, there are still remaining budget problems for pesticide enlargement registration tests for different kinds of crops. Thus, the pesticide registrations for the minor crops are serious tasks. As a general rule, the food classification adopted the Codex Classification of Foods and Animal Feeds. And though farmers cultivate their vegetables such as spinach and lettuce with no pesticide, the vegetables may still be affected by them because of some neighboring farmers spraying pesticides. This can lead to serious problems if pesticides are detected in vegetables. When the positive list was implemented for more than 10 years, this system is becoming more established in Japan but, various problems still remain and it is necessary to gather more information on pesticides.
The control of crop diseases still largely relies on spray applications of standard synthetic fungicides. As a result, the development of fungicide resistance by pathogens is a major limiting factor for the control of diseases. In this paper, the recent outbreak of practical resistance to fungicides including sterol demethylation inhibitor (DMI), Quinone outside inhibitor (QoI), and succinate dehydrogenase inhibitor (SDHI) fungicides as well as the progress of related research will be discussed. To combat resistance development, the Research Committee on Fungicide Resistance, the Phytopathological Society of Japan, was established in 1991 and has been conducting several activities. The Committee made a guideline indicating how to use at-risk fungicides. The occurrence of fungicide resistance may rather increase in the future as the choice of fungicides is often difficult due to the lack of effective alternatives. Development and integration of disease management tools such as disease-resistant or -tolerant cultivars and non-fungitoxic disease resistance inducers need to be accelerated more rapidly not only to dissolve the problem of fungicide resistance but also to reply public concerns about agrochemicals.
Growing resistance to insecticides, especially pyrethroids, poses an increased risk for insect control world-wide. Thus, alternative compounds are urgently needed. Accordingly, my laboratory has been investigating synthetic materials, as well as natural products, which are an attractive source of new chemistries. We have examined the insecticidal and synergistic activity of new compounds using Drosophila melanogaster and the mosquitoes Aedes aegypti and Anopheles gambiae as model insects. In addition, we have also been investigating the modes of action of experimental molecules in various physiological preparations.
Natural product research included thymol, which was toxic to Ae. aegypti adults at doses (3-50 μg/mg) similar to published toxicities for the cabbage looper larvae, Trichoplusia ni. On homomultimeric Anopheles gambiae GABA receptor-chloride channel complex expressed in Xenopus laevis oocytes, thymol acts as a positive allosteric modulator, increasing the potency and maximal effectiveness of applied GABA, consistent with the sluggish paralysis it elicits in exposed insects. Other studies investigated matrine; a bioactive component extracted from Sophora flavescens that is used as the main ingredient in Chinese bio-pesticidal products. Matrine caused flaccid paralysis in headless fourth instar larvae of Ae. aegypti (50% paralysis in 5 hours at 8 ppm) and was toxic to adult females by contact (topical LD50 = 258 ng/mg). Adult toxicity was increased about 2-fold by pretreatment with the mono-oxygenase inhibitor, piperonyl butoxide. Interestingly, this compound was much less effective on D. melanogaster in either glass contact or feeding bioassays. Adult mosquito knockdown was rapid, with little or no expression of hyperactivity or hyperexcitability. Matrine (ca. 1 mM) had effects similar to thymol on expressed An. gambiae GABA receptors, and reduced EPSP amplitude at the Musca domestica neuromuscular junction, without any evidence of neuroexcitation or membrane depolarization. These physiological actions are sufficient to explain the whole animal intoxication by matrine, but require relatively high concentrations to manifest themselves.
Other studies tested a series of potassium channel blockers, including 1-((2-chlorophenyl)diphenylmethyl)-1H-pyrazole (TRAM-34), 11-dansylaminoundecanoic acid (DAUDA), and 5-hydroxydecanoic acid (5-HDC) as insecticides and synergists of pyrethroids. We also evaluated the action of these compounds in patch clamp recordings of engineered HEK cells expressing Anopheles gambiae Kv2.1 channels. Patch clamp studies revealed that fatty acid compounds without functional groups in the alkyl chain (e.g., decanoate, DAUDA) yielded a more potent blocking action on Kv2.1 currents than substituted fatty acids (e.g., 5-HDC). Also, in comparison to 2-methoxy-N-((1-phenylcyclopentyl)methyl)benzamide (2S-65465), a known Kv2 channel blocker (IC50 = 100 nM), decanoate and DAUDA were 6-fold and 12-fold less active, respectively, as blockers of potassium current. TRAM-34 was the least potent inhibitor tested in patch clamp studies (IC50 = 30 uM). When tested on D. melanogaster CNS, the compounds typically gave an initial increase in firing rate, followed by a decrease, both effects at micromolar concentrations. Various toxicity assays showed the same potency ranking as that obtained through patch-clamp recordings, indicating a possible connection between channel block and whole organism effects. In order to possibly improve the insecticidal activity of the fatty acids, we synthesized derivatized analogs (e.g., methyl esters) presumed to better penetrate the cuticular barrier, but activity did not improve. Finally, in contrast to a published patent, we found that fatty acids did not show much synergism with pyrethroids. The implications of this work for resistance management will be discussed.
Herbicides have consistently contributed to yield increases in crop production for many decades however, those same herbicides are facing the loss of effectiveness because of the rapid spread of weed resistance. Since the first instance of herbicide resistance to triazine herbicides over 50 years ago, resistant biotypes have been observed to the major herbicides numbering more than 150 different weed species due to excessive use of single mode of action (MoA)treatments combined with limited crop rotation practices. In the US, the most well-known broad-spectrum herbicide used in major crops, glyphosate is facing huge challenges due to the appearance of many resistant weed species.
The consequences of the loss of effectiveness of the current herbicide choices, coinciding with an increasing world population with improved living standards, is beginning to present a severe constraint on food security globally. Unfortunately, the agriculture industry has been unable to find any new mechanism in the last 30 years. The absence of choices of novel active ingredients along with the increased costs of developing new entities is forcing the industry to rely on older modes of action which, with limited application, means lower annual yields of the major crops as the number of resistant weed species increases.
The Chemical Genomics group in FMC Agricultural Solutions Discovery has been building ‘Chemistry to Gene’ (C2G) capability to identify new MoAsby applying chemical genomics tools. We have recently discovered that compounds described in WO2017075559A1, are potent selective herbicides with novel action that control many grasses. As a result of knowledge of the mechanism of this area of chemistry, we have extended the work to include a ‘Gene to Chemistry’ (G2C) approach to provide new structural starting points for more synthesis projects.
SE Award Ceremony and Special Lecture of the Winner
해충의 발생은 생물적 및 비생물적 요인과 밀접하게 관련되어 있다. 하지만 근년의 해충 발생양상은 생물적 요인보다 비생물적 요인에 의해 더욱 큰 영향을 받는 것으로 여겨진다. 즉 지구온난화로 인해 월동하는 해충 개체군의 증가 및 남방계 해충의 서식지의 북상, 산림 및 농업생태계의 변화로 인한 해충 발생의 다양성과 역동성 제고, 교역량 증가로 인한 외래해충의 유입증가 및 정착에 따른 돌발적 대발생 등을 들 수 있다. 그리하여 해충에 의한 농작물의 안전 및 안정생산이 이전보다 크게 위협받게 되었고, 농업현장에서 해충의 효과적 관리를 위한 실용적 기술개발은 더욱 강하게 요구되고 있다.
국내에서 노린재류는 2000년 이후부터 발생량이 크게 증가하여 콩과 및 과수작물 등의 수량과 품질을 크게 떨어뜨리는 주요한 해충으로 인식되어 있다. 두류 및 과수류에 발생하는 노린재의 종류는 다양하지만, 주요 노린재류는 크게 호리허리노린재과(Alydidae)와 노린재과(Pentatomidae)로 구분할 수 있다. 이들 노린재류는 형태적 차이뿐만 아니라 비행성과 이동성 등에서 뚜렷한 행동적 차이를 가지고 있다. 그로인해 톱다리개미허리노린재는 통발트랩과 펀넬트랩으로 잘 포획할 수 있으나, 썩덩나무노린재와 갈색날개노린재는 유인되지 않는다. 그리하여 노린재의 종류에 관계없이 범용으로 노린재류를 잘 포획할 수 있는 트랩개발이 필요하게 되어 로케트트랩(Rocket trap)을 개발하게 되었다. 농업해충 가운데는 양성주광성(Positive phototaxis)을 가져 밤에 불빛으로 모여드는 특성을 가진 해충이 많이 있다. 스마트트랩(Smart trap)은 낮에 태양광을 축전하고 밤에 해충이 선호하는 파장의 램프를 작동시켜 나비목, 딱정벌레목, 매미목 및 노린재목 등의 해충을 친환경적으로 대량 포획할 수 있는 포충기를 개발하였다. 벼 및 밭작물 재배포장, 과수원, 플랜테이션 농장, 휴양림, 전원주택 및 골프장 등에 스마트트랩을 설치하여 주광성 해충을 효과적으로 포획하는데 국내·외에서 사용되고 있다. 또한 약제를 가열하지 않고 나노입자로 분무하여 시설작물, 축사 및 버섯재배사 등에서 문제되는 병해충을 생력적으로 관리할 수 있는 비가열식무인연막기를 개발하여 그 효과를 검정하고 있는 단계이다.
아직도 많이 부족하고 어느 것 하나 제대로 한 것 없는 것 같은데, 2018년 한국응용곤충학회 추계 학술발표회에서 제 1회 응용곤충학상을 받게 된 것은 개인적으로 큰 영광이라 하지 않을 수 없다. 그동안 함께 연구해온 동료와 학술적 동기를 유발시킨 한국응용곤충학회 그리고 트랩개발에 적극 협조해준 산업계 등에 깊은 감사를 드립니다.
Fumigation - one of the chemical methods - is the art of dispensing and applying gaseous substances especially for the purpose of disinfecting. It is an old and widely used technique for disinfestation of postharvest grain, fruit and vegetable. In a fumigation procedure, a gas is added to an enclosure for the purpose of controlling or eliminating undesirable organisms. The organisms may be pests of various types - such as insects, rodents, mites, and birds - or micro-organisms, or particular plants or seeds. The enclosure can be made from a diverse range of materials, including metal, concrete, bricks, mud and various plastic membranes. It is necessary to contain the fumigant while it acts on the target organism and to restrict its escape into areas where it may be dangerous to human health. In many situations fumigation may be the only feasible process for pest control as it does not require the commodity to be moved. Neither might it need specialized apparatuses, electricity, or manpower, and is relatively easy to apply in comparison with other methods, for example, heating and irradiation, as well as the use of protectants to control insects. Because fumigation is often the cheapest and most effective process available, it plays a major, world-wide, role in preserving commodities. However, researchers and operators not always fully understand principle of fumigant and fumigation practice to ensure select right fumigant and exposure time on different target insect pests and host commodities as well as application methods.
Many herbivorous insects sequester plant defense compounds from their host plants to protect themselves from natural enemies. In plants, these defense compounds are often stored as protoxins separated from their activating enzymes. A well-known example is the glucosinolate-myrosinase defense system in plants of the order Brassicales. When plant tissue is ingested by herbivores, glucosinolates are hydrolyzed by the enzyme myrosinase to form highly reactive isothiocyanates. We previously reported that flea beetles of the genus Phyllotreta selectively sequester high amounts of glucosinolates from their crucifer host plants, and convergently evolved their own myrosinase which enables them to utilize sequestered glucosinolates for their own purposes (Beran et al., 2014). The presence of intact glucosinolates in these beetles suggests that despite tissue damage, ingested glucosinolates are not activated by the plant myrosinase. Rapid and efficient glucosinolate uptake from the gut lumen into gut epithelial cells can prevent hydrolysis and thus might be crucial to overcome this activated plant defense.
We use the horseradish flea beetle Phyllotreta armoraciae as a model to study the molecular basis of sequestration in insects. In short-term feeding experiments, we showed that ingested glucosinolates are rapidly sequestered in the foregut. To identify the transporters that mediate glucosinolate import from the foregut lumen into gut epithelial cells, we focused on the MFS transporter family, which is known to transport a wide range of substrates. A phylogenetic analysis of putative MFS transporter sequences identified in P. armoraciae and other beetles revealed several specifically expanded clades in P. armoraciae. Out of 21 candidate genes that were heterologously expressed in Sf9 cells, nine showed glucosinolate transport activity in vitro. Interestingly, most candidate genes were exclusively expressed in the malpighian tubules, and two genes were additionally expressed in the foregut. We currently elucidate the function of these transporters in glucosinolate sequestration in vivo using RNAi.
To better understand the function of sequestered glucosinolates, we performed bioassays with P. armoraciae larvae and the generalist predatory ladybird Harmonia axyridis. Upon predator attack, P. armoraciae larvae emitted high amounts of isothiocyanates and ladybird larvae stopped feeding within a few seconds and were highly irritated. However, silencing myrosinase gene expression in P. armoraciae larvae led to increased mortality compared to control larvae in survival assays with ladybird larvae. Our results demonstrate how Phyllotreta use plant defense metabolites to defend themselves against predators.
Monitoring is an important component in the detection, surveillance and eradication of invasive insect pests. In particular, the availability of useful attractants and effective traps is critical in establishing a new surveillance program for quarantine pests. A powerful, species-specific attractant is desirable when precision early detection is needed. However, such an ideal attractant is not often available when the introduction of a new surveillance program is urgent. In reality, the combination of available monitoring means is adopted, which in turn requires the subsequent development of optimum monitoring strategy with these available means. Various species of fruit flies, belonging to the genus Bactrocera in particular, are serious threat to Korea, and developing systematic monitoring systems is needed against the invasion of the fruit flies. Effective male attractants, such as methyl eugenol and cue lure, and traps are currently available for some species such as B. dorsalis, B. tryoni, and B. carambolae. However, such attractants are yet to be developed for many other fruit fly species. The strong attraction of the striped fruit fly, B. scutellata, being present in large numbers in Korean fields to cue lure can be a potential obstacle in monitoring other species of fruit flies attracted to the same compound. Various attractants based on protein hydrolysates are also useful in monitoring fruit flies since they are attractive to both males and females of fruit flies. However, it is desirable to develop these protein-based baits into more species-specific attractants. Monitoring techniques for some important quarantine fruit flies are further discussed.
DNA bacoding is a popular DNA diagnostic technique especially for specific and generic level identification during various quarantine activities. BOLD Systems, an internet accessible DNA barcode data portal, currently includes over 12,000 DNA barcodes for the fruit fly family Tephritidae, of which 8,940 barcodes are open to public. These data represent 655 tephritid species, majority of which are pest species. These figures are rapidly increasing as the tephritid barcoding research is increasing every year. Therefore, BOLD has established as the most important DNA barcode source for tephritid identification. It is, therefore, also important to understand the limitations and problems of the DNA barcoding analysis. We here discussed the following potential problems and their possible solutions: (1) misidentification of species listed in BOLD; (2) sibling species with identical or near-identical barcodes; (3) NUMT (nuclear mitochondrial DNA) or pseudogene; and (4) introgression by hybridization between closely related species.
금지급 과실파리 침입시 대응조치(박멸프로그램) 실행과정에서 박멸프로그램의 종료는 3세대기간 동안 미포획되는 상황을 기준으로 하고 있다. 본 연구에서는 카람볼라과실파리(Bactocera carambolae), 구아바과실파리(B. correcta), 남방고추과실파리(B. latifrons), 작은퀸즐랜드과실파리(B. neohumeralis), 일본귤과실파리(B. tsuneonis) 등 5종에 대한 기존 온도발육자료를 바탕으로 세대기간 추정에 필요한 적산온도 모형을 제시하였다. 각 종의 세대기간 추정에 필요한 발육 영점온도와 적산온도는 칼람볼라과실파리 11.8℃와 384.6 Degree days(DD), 구아바과실파리 11.6℃와 454.5 DD, 남방고추과실파리 10.4℃와 517.5 DD, 작은퀸즐랜드과실파리 9.2℃와 467.8 DD로 추정되었다. 일화성인 일본귤과실파리의 경우는 월동용의 우화모형(발육영점은 11.3℃, 625 DD)을 이용하는 방법을 제안하였다.
약 5,000 종 가량의 종다양성을 보이는 과실파리과(Tephritidae)는 농작물에 심각한 피해를 주는 6 속(Bactrocera, Ceratitis, Dacus, Zeugodacus, Anastrepha, Rhagoletis) 해충군을 포함하고 있다. 이들이 비록 아열대 지역에 분포하고 있으나, 기후변화 및 국제교역량 증가로 국내 침입이 빈번하여 지고 이에 대한 한국형 검역 매뉴얼의 개발이 시급하다. 이 매뉴얼은 금지급 과실파리의 동정 기술, 긴급 및 상시 모니터링 기술, 침입 후 확산 지역 및 발생 세대 예측 기술, 그리고 박멸기술을 포함하게 된다. 본 발표는 이 가운데 박멸기술로서 수컷박멸기술(male annihilation technique: MAT), 암컷박멸기술(female annihilation technique: FAT), 그리고 불임충방사기술(sterile insect release technique: SIT)을 소개한다.
Forest pests are a major threat to forest ecological and economic health. For this reason, the monitoring for forest pests was necessary and the monitoring program has begun from 1968 in Korea. During past 50 years, forest pests in pine forests have been shifting from pine moth (Dendrolimus spectabilis) via pine needle gall midge (PNGM, Thecodiplosis japonensis) to pine wilt disease (PWD). The pine moth is a native species to Korea and its outbreaks were recorded even 500 years ago. It was the major forest pests in Korea from 1950s to 1970s. The cause of its decline was probably due to increase in activities of microorganism-type natural enemy. In 1980s and 1990s, PNGM was the major forest pests in Korea. It invaded to Korea in 1929 and dispersed to nationwide in 1992. The suite of parasitic wasps to PNGM at least partially contributed to decline of PNGM on the basis of long term monitoring research. After 2000s, the pine wilt disease caused by Bursaphelenchus xylophilus, an invasive species and vectored by Monochamus alternatus and M. saltuarius, native species was the major forest pest in Korea. These results showed that threat by invasive species on the forest health was increase and natural enemies at least partially contribute to stabilize outbreak of forest pests. Therefore, the further researches and monitoring on invasive species and roles of natural enemies are intensively conducted.
Forest insect pests monitoring provides essential information for forest management against their outbreaks. Long-term monitoring data for forest insect pests have been collected by National Institute of Forest Science at national level since 1968. Forest insect pests for long-term monitoring include pine needle gall midge, black pine bast scale, fall webworm, pine moth, spotted lanternfly, etc. The monitoring data were analyzed effect of meteorological factors on the outbreaks of sporadic forest insect pests. Our results showed that meteorological factors can influenced on outbreak of forest insects. The species including Lepidoptera has more occurred when fall and winter temperature were relatively high during the period, suggesting that their outbreaks depends on mortality rate during winter diapause. In Diptera, species abundance was positively related with amount of precipitation in spring but negatively related with summer temperature. The species belong to Hymenoptera was also more abundant when spring temperature was relatively warm. These results can provide useful information for predict potential forest insect pests from climate change.
Forest insect pests are severe disturbance factors in forest ecosystems, inducing the diverse negative impacts on the forestry economy, ecosystem service, biodiversity, and sustainable ecosystem management. Majority of forest insect pests are invasive species in many countries. To understand the occurrence patterns including population dynamics and dispersal of species, ecological modelling is popularly considered as a tool. Ecological modelling can provide information that is required for decision making through hazard ratings, the examination of potential impacts, and the prediction of dispersal patterns for forest pests. In this study, we review the modelling methods and present some case studies conducted in Korean forests.
The black pine bast scale, Matsucoccus thunbergianae Miller et Park, is one of the severe pest to pine forests in South Korea. In 1963, a severe pine damage by unknown causes were reported at Goheung region and it turned out that the damage was caused by the black pine bast scale, M. thunbergianae 20 years later. The black pine bast scale have been causing serious damage to Japanese black pine forests in the east and southwestern coastal area of South Korea and its distribution has been expanded. The areas of Japanese black pine forests damaged by M. thunbergianae was 4,043ha in 41 cities or districts in 2017. In males, two nymphal instars are followed by wingless preadult, the pupa, and the adult, whereas the female adult directly emerges from the second nymphal instar. According to recent sex pheromone survey for male adult, M. thunbergianae occur mainly single generation in South Korea with possibility its phenology was advanced probably due to climate change. Until now, the most effective measure to control the black pine bast scale is to trunk injection with insecticides after thinning of a damaged pine forest.
During the last few decades, we have faced problems caused by some invasive forest pests such as the black locust gall midge, spotted lanternfly, citrus flatid planthopper, pine wood nematode, etc. As for the pine wood nematode, it is originated from the US and found two insect vectors which previously were not considered as insect pests at all in Korea. Now those two Monochamus cerambycids are nothing but insect pests to be controlled in order to slow down the spread of the pine wood nematode. Here we introduce the results of the surveys seeking out parasitoids which can be used for biological controls against those pests. In addition we also make a suggestion to keep our efforts to utilize those beneficial insects as eco-friendly control measures, not simply depending on physical or chemical methods.
Individual plants can provide space for various herbivore communities, and multiple herbivores often colonize different parts of the same plant. Plants can therefore play an important role in shaping community composition in ecosystems by mediating interactions among herbivore. Plant-mediated interactions among different folivores or between above-and below-ground herbivores are relatively well understood. However, although important for structural support and nutritional transport, the stem is largely unknown in how it responds to stem-feeding herbivores, or whether leaf- and stem-responses to herbivore attack are integrated. Interestingly, I found that JA signaling is also important for resistance to the stem herbivore, and, interestingly, that N. attenuata induced lignin and chlorogenic acid in stems in the face of stem herbivore attack. I also further found that plant inducible defenses in the pith and in the leaf are not systemically induced other tissues, but systemic induction of JA signaling was asymmetric between the stem and the leaf. I conclude that tissue-localized defense responses allow tissue-specialized herbivores to share the same host and occupy different chemical defense niches in the same hostplant.
Many insects are able to feed on crucifers despite the presence of a potent activated defense system known as the mustard oil bomb. In damaged tissue, mustard oil glucosides (glucosinolates) are hydrolyzed by the enzyme myrosinase to form toxic mustard oils (isothiocyanates). Here, we analyzed how the the cabbage stem flea beetle Psylliodes chrysocephala, a key pest of oilseed rape, copes with this chemical defense. First, we found that P. chrysocephala prevents the activation of ingested glucosinolates by two different strategies, a) by sequestering glucosinolates and b) by converting glucosinolates to desulfo-glucosinolates. Our next aim was to identify the sulfatase enzyme(s) responsible for the detoxification of glucosinolates in P. chrysocephala. Nine arylsulfatase-like genes were identified in the transcriptome of P. chrysocephala, and five of them showed glucosinolate sulfatase activity upon heterologous expression in Sf9 cells. By using RNAi, we confirmed that PcGSS1 and PcGSS2 are active towards benzenic and indolic glucosinolates in P. chrysocephala adults in vivo. However, in feeding experiments, the proportion of sequestered and desulfated glucosinolates ranged from 26 to 35% which suggests that these strategies alone are likely not sufficient to overcome the chemical plant defense. Indeed, P. chrysocephala additionally conjugates isothiocyanates to glutathione and metabolizes them via the conserved mercapturic acid pathway. In summary, the cabbage stem flea beetle avoids isothiocyanate formation by specialized strategies (sequestration and desulfation), but also relies on a conserved detoxification pathway to prevent toxicity of isothiocyanates.
We investigated the detoxification strategies of Helicoverpa armigera and Heliothis virescens, which allow them to feed successfully on cotton plants that produce toxic gossypol as a chemical defense compound. First, we tested CYP6AE14, a proposed candidate enzyme for gossypol detoxification, for its ability to detoxify gossypol. In incubation assays with gossypol and heterologously expressed CYP6AE14 no metabolites were detected. Our data show that CYP6AE14 is not directly involved in gossypol metabolism, at least under the assay conditions tested, but rather takes part in the general stress response of the herbivores to plant toxins. Second, we discovered that H. armigera and H. virescens excrete a large proportion (50%) of unmetabolized gossypol in the feces, but additionally metabolize gossypol by glycosylation. Analysis of larval feces revealed three monoglycosylated and up to five diglycosylated gossypol isomers when larvae fed on gossypol-supplemented diet. Based on their expression patterns we selected H. armigera candidate UGT genes and functionally expressed the respective proteins in insect cells. In enzymatic assays, we showed that UGT41B3 and UGT40D1 are capable of glycosylating gossypol mainly to a diglycosylated gossypol isomer that is characteristic for H. armigera and is absent in H. virescens feces. We offer novel insights into the detoxification mechanism of the plant defensive toxin, gossypol, by two generalist herbivores.
The cotton bollworm, Helicoverpa armigera is one of the most polyphagous and cosmopolitan pest species in world wide including Korea. It also showed high level of resistance against various types of insecticide. To set the integrated resistant management program, first, we tried to identify the insecticide resistant mechanism via transcriptome analysis of coding and non-coding RNAs using 4 strains (Australian susceptible and resistant strains, Korean and Brazilian resistant strains, additional a sub-lethal dose insecticide treatment in Korean resistant strain). From the illumina based RNAseq data sets with genome information, some resistant involved detoxification genes and long non-coding RNAs were discovered. Second, following molecular markers were developed from resistant strain specific amino acid substitution from those candidate genes. Third, functionally identified genes’ markers were applied in field populations using some molecular diagnostic tools such as LAMP (loop mediated isothermal amplification). Now additional functional analysis is going on for these un-characterized candidate genes and long non-coding RNAs.