Enhanced resistance to soybean cyst nematode in transgenic soybean via host-induced silencing of vital Heterodera glycines genes.

Soybean cyst nematode (SCN, Heterodera glycines Ichinohe) is the most economically damaging pathogen affecting soybean production worldwide. Host-induced gene silencing provides a promising approach to confer resistance to plant parasitic nematodes. In the present study, we produced stable transgenic soybean plants individually harboring the inverted repeats of three essential H. glycines genes, Hg-rps23, Hg-snb1, and Hg-cpn1, and evaluated their resistance to SCN infection. Molecular characterization confirmed the stable integration of the hairpin double stranded (ds) RNA in host plants. Inoculation assays with SCN race 3 showed significant reduction of female index (FI, 11.84 ~ 17.47%) on the roots of T4 transgenic plants, with 73.29 ~ 81.90% reduction for the three RNA interference (RNAi) constructs, compared to non-transformed plants (NT, 65.43%). Enhanced resistance to SCN race 3 was further confirmed in subsequent generations (T5) of transgenic soybean. Moreover, when inoculated with SCN race 4 which was considered highly virulent to most of soybean germplasms and varieties, transgenic soybean plants also exhibited reduced FIs (9.96 ~ 23.67%) and increased resistance, relative to the NT plants (46.46%). Consistently, significant down-regulation in transcript levels of the Hg-rps23, Hg-snb1, Hg-cpn1 genes were observed in the nematodes feeding on the transgenic roots, suggesting a broad-spectrum resistance mediated by the host-mediated silencing of vital H. glycines genes. There were no significant differences in morphological traits between transgenic and NT soybean plants under conditions with negligible SCN infection. In summary, our results demonstrate the effectiveness of host-induced silencing of essential H. glycines genes to enhance broad-spectrum SCN resistance in stable transgenic soybean plants, without negative consequences on the agronomic performance.

Novel approaches to circumvent the devastating effects of pests on sugarcane.

Sugarcane (Saccharum officinarum L.) is a cash crop grown commercially for its higher amounts of sucrose, stored within the mature internodes of the stem. Numerous studies have been done for the resistance development against biotic and abiotic stresses to save the sucrose yields. Quality and yield of sugarcane production is always threatened by the damages of cane borers and weeds. In current study two problems were better addressed through the genetic modification of sugarcane for provision of resistance against insects and weedicide via the expression of two modified cane borer resistant CEMB-Cry1Ac (1.8 kb), CEMB-Cry2A (1.9 kb) and one glyphosate tolerant CEMB-GTGene (1.4 kb) genes, driven by maize Ubiquitin Promoter and nos terminator. Insect Bio-toxicity assays were carried out for the assessment of Cry proteins through mortality percent of shoot borer Chilo infuscatellus at 2nd instar larvae stage. During V0, V1 and V2 generations young leaves from the transgenic sugarcane plants were collected at plant age of 20, 40, 60, 80 days and fed to the Chilo infuscatellus larvae. Up to 100% mortality of Chilo infuscatellus from 80 days old transgenic plants of V2 generation indicated that these transgenic plants were highly resistant against shoot borer and the gene expression level is sufficient to provide complete resistance against target pests. Glyphosate spray assay was carried out for complete removal of weeds. In V1-generation, 70-76% transgenic sugarcane plants were found tolerant against glyphosate spray (3000 mL/ha) under field conditions. While in V2-generation, the replicates of five selected lines 4L/2, 5L/5, 6L/5, L8/4, and L9/6 were found 100% tolerant against 3000 mL/ha glyphosate spray. It is evident from current study that CEMB-GTGene, CEMB-Cry1Ac and CEMB-Cry2A genes expression in sugarcane variety CPF-246 showed an efficient resistance against cane borers (Chilo infuscatellus) and was also highly tolerant against glyphosate spray. The selected transgenic sugarcane lines showed sustainable resistance against cane borer and glyphosate spray can be further exploited at farmer's field level after fulfilling the biosafety requirements to boost the sugarcane production in the country.

A Bacillus thuringiensis Cry protein controls soybean cyst nematode in transgenic soybean plants.

Plant-parasitic nematodes (PPNs) are economically important pests of agricultural crops, and soybean cyst nematode (SCN) in particular is responsible for a large amount of damage to soybean. The need for new solutions for controlling SCN is becoming increasingly urgent, due to the slow decline in effectiveness of the widely used native soybean resistance derived from genetic line PI 88788. Thus, developing transgenic traits for controlling SCN is of great interest. Here, we report a Bacillus thuringiensis delta-endotoxin, Cry14Ab, that controls SCN in transgenic soybean. Experiments in C. elegans suggest the mechanism by which the protein controls nematodes involves damaging the intestine, similar to the mechanism of Cry proteins used to control insects. Plants expressing Cry14Ab show a significant reduction in cyst numbers compared to control plants 30 days after infestation. Field trials also show a reduction in SCN egg counts compared with control plants, demonstrating that this protein has excellent potential to control PPNs in soybean.

Targeting of anti-microbial proteins to the hyphal surface amplifies protection of crop plants against Phytophthora pathogens.

Phytophthora pathogens are a persistent threat to the world's commercially important agricultural crops, including potato and soybean. Current strategies aim at reducing crop losses rely mostly on disease-resistance breeding and chemical pesticides, which can be frequently overcome by the rapid adaptive evolution of pathogens. Transgenic crops with intrinsic disease resistance offer a promising alternative and continue to be developed. Here, we explored Phytophthora-derived PI3P (phosphatidylinositol 3-phosphate) as a novel control target, using proteins that bind this lipid to direct secreted anti-microbial peptides and proteins (AMPs) to the surface of Phytophthora pathogens. In transgenic Nicotiana benthamiana, soybean, and potato plants, significantly enhanced resistance to different pathogen isolates was achieved by expression of two AMPs (GAFP1 or GAFP3 from the Chinese medicinal herb Gastrodia elata) fused with a PI3P-specific binding domain (FYVE). Using the soybean pathogen P. sojae as an example, we demonstrated that the FYVE domain could boost the activities of GAFPs in multiple independent assays, including those performed in vitro, in vivo, and in planta. Mutational analysis of P. sojae PI3K1 and PI3K2 genes of this pathogen confirmed that the enhanced activities of the targeted GAFPs were correlated with PI3P levels in the pathogen. Collectively, our study provides a new strategy that could be used to confer resistance not only to Phytophthora pathogens in many plants but also potentially to many other kinds of plant pathogens with unique targets.

Managing the Invasive Fall Armyworm through Biotech Crops: A Chinese Perspective.

In late 2018, the highly destructive and polyphagous fall armyworm was first detected in China. It is now a major economic threat to corn production. In this article, the main control strategies that are available are reviewed and prospects to manage this pest with Bacillus thuringiensis (Bt) corn in China are discussed.

Understanding the potential impact of continued seed treatment use for resistance management in Cry51Aa2.834_16 Bt cotton against Frankliniella fusca.

Transgenic cotton expressing Cry51Aa2.834_16 Bt toxin (hereafter referred to as MON 88702) has the potential to be an important tool for pest management due to its unique activity against tobacco thrips, Frankliniella fusca. Unlike other Bt toxins targeting lepidopteran cotton pests, MON 88702 does not cause direct mortality but has an antixenotic effect that suppresses F. fusca oviposition. Previous work has shown neonicotinoid seed treated (NST) crops have similar behavioral effects on thrips. This study used non-choice and common garden experiments to examine how the presence of MON 88702 cotton and soybean (another F. fusca host) with and without NSTs might alter F. fusca infestation distributions. In a no-choice environment, significant larval establishment differences were observed, with untreated soybean plants becoming most heavily infested. In choice experiments, plants expressing MON 88702 or were neonicotinoid treated had significantly lower larval establishment. Larval density decreased as dispersal distance increased, suggesting reproductive decisions were negatively related to distance from the release point. Understanding how F. fusca responds to MON 88702 in an environment where adults can choose among multiple host plants will provide valuable context for projections regarding design of MON 88702 resistance refuges. Reduced larval establishment on NST cotton and soybean suggests that area-wide use of NSTs could reduce the number of susceptible F. fusca generated in unstructured crop refuges for MON 88702. These results also suggest that although the presence of NST MON 88702 could suppress reproduction and resistance selection, over time this benefit could erode resulting in increased larval establishment on NST cotton and soybean due to increased frequency of neonicotinoid resistant F. fusca populations.

Host-parasite tissue adhesion by a secreted type of ß-1,4-glucanase in the parasitic plant Phtheirospermum japonicum.

Tissue adhesion between plant species occurs both naturally and artificially. Parasitic plants establish intimate relationship with host plants by adhering tissues at roots or stems. Plant grafting, on the other hand, is a widely used technique in agriculture to adhere tissues of two stems. Here we found that the model Orobanchaceae parasitic plant Phtheirospermum japonicum can be grafted on to interfamily species. To understand molecular basis of tissue adhesion between distant plant species, we conducted comparative transcriptome analyses on both infection and grafting by P. japonicum on Arabidopsis. Despite different organs, we identified the shared gene expression profile, where cell proliferation- and cell wall modification-related genes are up-regulated. Among genes commonly induced in tissue adhesion between distant species, we showed a gene encoding a secreted type of ß-1,4-glucanase plays an important role for plant parasitism. Our data provide insights into the molecular commonality between parasitism and grafting in plants.

Reduced Membrane-Bound Alkaline Phosphatase Does Not Affect Binding of Vip3Aa in a Heliothis virescens Resistant Colony.

The Vip3Aa insecticidal protein from Bacillus thuringiensis (Bt) is produced by specific transgenic corn and cotton varieties for efficient control of target lepidopteran pests. The main threat to this technology is the evolution of resistance in targeted insect pests and understanding the mechanistic basis of resistance is crucial to deploy the most appropriate strategies for resistance management. In this work, we tested whether alteration of membrane receptors in the insect midgut might explain the >2000-fold Vip3Aa resistance phenotype in a laboratory-selected colony of Heliothis virescens (Vip-Sel). Binding of 125I-labeled Vip3Aa to brush border membrane vesicles (BBMV) from 3rd instar larvae from Vip-Sel was not significantly different from binding in the reference susceptible colony. Interestingly, BBMV from Vip-Sel larvae showed dramatically reduced levels of membrane-bound alkaline phosphatase (mALP) activity, which was further confirmed by a strong downregulation of the membrane-bound alkaline phosphatase 1 (HvmALP1) gene. However, the involvement of HvmALP1 as a receptor for the Vip3Aa protein was not supported by results from ligand blotting and viability assays with insect cells expressing HvmALP1.

The atypical E2F transcription factor DEL1 modulates growth-defense tradeoffs of host plants during root-knot nematode infection.

In plants, growth-defense tradeoffs are essential for optimizing plant performance and adaptation under stress conditions, such as pathogen attack. Root-knot nematodes (RKNs) cause severe economic losses in many crops worldwide, although little is known about the mechanisms that control plant growth and defense responses during nematode attack. Upon investigation of Arabidopsis thaliana infected with RKN (Meloidogyne incognita), we observed that the atypical transcription factor DP-E2F-like 1 (DEL1) repressed salicylic acid (SA) accumulation in RKN-induced galls. The DEL1-deficient Arabidopsis mutant (del1-1) exhibited excessive SA accumulation in galls and is more resistant to RKN infection. In addition, excessive lignification was observed in galls of del1-1. On the other hand, the root growth of del1-1 is reduced after RKN infection. Taken together, these findings suggest that DEL1 plays an important role in the balance between plant growth and defense responses to RKN infection by controlling SA accumulation and lignification.

MiDaf16-like and MiSkn1-like gene families are reliable targets to develop biotechnological tools for the control and management of Meloidogyne incognita.

Meloidogyne incognita is a plant-parasitic root-knot nematode (RKN, PPN) responsible for causing damage to several crops worldwide. In Caenorhabditis elegans, the DAF-16 and SKN-1 transcription factors (TFs) orchestrate aging, longevity, and defense responses to several stresses. Here, we report that MiDaf16-like1 and MiSkn1-like1, which are orthologous to DAF-16 and SKN-1 in C. elegans, and some of their targets, are modulated in M. incognita J2 during oxidative stress or plant parasitism. We used RNAi technology for the stable production of siRNAs in planta to downregulate the MiDaf16-like1 and MiSkn1-like1 genes of M. incognita during host plant parasitism. Arabidopsis thaliana and Nicotiana tabacum overexpressing a hairpin-derived dsRNA targeting these genes individually (single-gene silencing) or simultaneously (double-gene silencing) were generated. T2 plants were challenged with M. incognita and the number of eggs, galls, and J2, and the nematode reproduction factor (NRF) were evaluated. Our data indicate that MiDaf16-like1, MiSkn1-like1 and some genes from their networks are modulated in M. incognita J2 during oxidative stress or plant parasitism. Transgenic A. thaliana and N. tabacum plants with single- or double-gene silencing showed significant reductions in the numbers of eggs, J2, and galls, and in NRF. Additionally, the double-gene silencing plants had the highest resistance level. Gene expression assays confirmed the downregulation of the MiDaf16-like1 and MiSkn1-like1 TFs and defense genes in their networks during nematode parasitism in the transgenic plants. All these findings demonstrate that these two TFs are potential targets for the development of biotechnological tools for nematode control and management in economically important crops.

Soybean Resistance Locus Rhg1 Confers Resistance to Multiple Cyst Nematodes in Diverse Plant Species.

Cyst nematodes consistently threaten agricultural production, causing billions of dollars in losses globally. The Rhg1 (resistance to Heterodera glycines 1) locus of soybean (Glycine max) is the most popular resistance source used against soybean cyst nematodes (H. glycines). Rhg1 is a complex locus that has multiple repeats of an ≈30-kilobase segment carrying three genes that contribute to resistance. We investigated whether soybean Rhg1 could function in different plant families, conferring resistance to their respective cyst nematode parasites. Transgenic Arabidopsis thaliana and potato (Solanum tuberosum) plants expressing the three soybean Rhg1 genes were generated. The recipient Brassicaceae and Solanaceae plant species exhibited elevated resistance to H. schachtii and Globodera rostochiensis and to G. pallida, respectively. However, some negative consequences including reduced root growth and tuber biomass were observed upon Rhg1 expression in heterologous species. One of the genes at Rhg1 encodes a toxic version of an alpha-SNAP protein that has been demonstrated to interfere with vesicle trafficking. Using a transient expression assay for Nicotiana benthamiana, native Arabidopsis and potato alpha-SNAPs (soluble NSF [N-ethylamine sensitive factor] attachment protein) were found to compensate for the toxicity of soybean Rhg1 alpha-SNAP proteins. Hence, future manipulation of the balance between Rhg1 alpha-SNAP and the endogenous wild-type alpha-SNAPs (as well as the recently discovered soybean NSF-RAN07) may mitigate impacts of Rhg1 on plant productivity. The multispecies efficacy of soybean Rhg1 demonstrates that the encoded mechanisms can function across plant and cyst nematode species and offers a possible avenue for engineered resistance in diverse crop species.

Host-derived gene silencing of parasite fitness genes improves resistance to soybean cyst nematodes in stable transgenic soybean.

KEY MESSAGE: Soybean expressing small interfering RNA of SCN improved plant resistance to SCN consistently, and small RNA-seq analysis revealed a threshold of siRNA expression required for resistance ability. Soybean cyst nematode (SCN), Heterodera glycines, is one of the most destructive pests limiting soybean production worldwide, with estimated losses of $1 billion dollars annually in the USA alone. RNA interference (RNAi) has become a powerful tool for silencing gene expression. We report here that the expression of hairpin RNAi constructs, derived from two SCN genes related to reproduction and fitness, HgY25 and HgPrp17, enhances resistance to SCN in stably transformed soybean plants. The analyses of T3 to T5 generations of stable transgenic soybeans by molecular strategies and next-generation sequencing confirmed the presence of specific short interfering RNAs complementary to the target SCN genes. Bioassays performed on transgenic soybean lines targeting SCN HgY25 and HgPrp17 fitness genes showed significant reductions (up to 73%) for eggs/g root in the T3 and T4 homozygous transgenic lines. Targeted mRNAs of SCN eggs collected from the transgenic soybean lines were efficiently down-regulated, as confirmed by quantitative RT-PCR. Based on the small RNA-seq data and bioassays, it is our hypothesis that a threshold of small interfering RNA molecules is required to significantly reduce SCN populations feeding on the host plants. Our results demonstrated that host-derived gene silencing of essential SCN fitness genes could be an effective strategy for enhancing resistance in crop plants.

Transgenic RXLR Effector PITG_15718.2 Suppresses Immunity and Reduces Vegetative Growth in Potato.

Phytophthora infestans causes the severe late blight disease of potato. During its infection process, P. infestans delivers hundreds of RXLR (Arg-x-Leu-Arg, x behalf of any one amino acid) effectors to manipulate processes in its hosts, creating a suitable environment for invasion and proliferation. Several effectors interact with host proteins to suppress host immunity and inhibit plant growth. However, little is known about how P. infestans regulates the host transcriptome. Here, we identified an RXLR effector, PITG_15718.2, which is upregulated and maintains a high expression level throughout the infection. Stable transgenic potato (Solanum tuberosum) lines expressing PITG_15718.2 show enhanced leaf colonization by P. infestans and reduced vegetative growth. We further investigated the transcriptional changes between three PITG_15718.2 transgenic lines and the wild type Désirée by using RNA sequencing (RNA-Seq). Compared with Désirée, 190 differentially expressed genes (DEGs) were identified, including 158 upregulated genes and 32 downregulated genes in PITG_15718.2 transgenic lines. Eight upregulated and nine downregulated DEGs were validated by real-time RT-PCR, which showed a high correlation with the expression level identified by RNA-Seq. These DEGs will help to explore the mechanism of PITG_15718.2-mediated immunity and growth inhibition in the future.

Heat treatment alleviates the growth and photosynthetic impairment of transplastomic plants expressing Leishmania infantum Hsp83-Toxoplasma gondii SAG1 fusion protein.

Previously, we showed that transplastomic tobacco plants expressing the LiHsp83-SAG1 fusion protein displayed a chlorotic phenotype and growth retardation, while plants expressing the SAG1 and GRA4 antigens alone did not. We conducted a comprehensive examination of the metabolic and photosynthetic parameters that could be affecting the normal growth of LiHsp83-SAG1 plants in order to understand the origin of these pleiotropic effects. These plants presented all photosynthetic pigments and parameters related to PSII efficiency significantly diminished. However, the expression of CHLI, RSSU and LHCa/b genes did not show significant differences between LiHsp83-SAG1 and control plants. Total protein, starch, and soluble sugar contents were also greatly reduced in LiHsp83-SAG1 plants. Since Hsp90 s are constitutively expressed at much higher concentrations at high temperatures, we tested if the fitness of LiHsp83-SAG1 over-expressing LiHsp83 would improve after heat treatment. LiHsp83-SAG1 plants showed an important alleviation of their phenotype and an evident recovery of the PSII function. As far as we know, this is the first report where it is demonstrated that a transplastomic line performs much better at higher temperatures. Finally, we detected that LiHsp83-SAG1 protein could be binding to key photosynthesis-related proteins at 37 °C. Our results suggest that the excess of this molecular chaperone could benefit the plant in a possible heat shock and prevent the expected denaturation of proteins. However, the LiHsp83-SAG1 protein content was weakly decreased in heat-treated plants. Therefore, we cannot rule out that the alleviation observed at 37 °C may be partially due to a reduction of the levels of the recombinant protein.

In-planta expression of insecticidal proteins provides protection against lepidopteran insects.

The development of advanced biotechnological control strategies opens a new era of environment friendly pest management. The current study is part of such an effort, in which we developed a control strategy based on gene pyramiding that confers broad-spectrum resistance against lepidopteran (Helicoverpa armigera and Spodoptera litura) and hemipteran (Myzus persicae, Phenacoccus solenopsis, and Bemisia tabaci) insect pests. Previously, we reported a double gene construct expressing Hvt and lectin in tobacco (Nicotiana tabacum) plants under phloem specific promoters which confers resistance against hemipteran insects. Here we extended our studies by evaluating the advanced generation of these tobacco plants expressing hvt-lectin against lepidopteran insects. Tobacco plants expressing both toxins were tested against H. armigera and S. litura. Insect bioassay results showed 100% mortality of H. armigera within 48-72 hours and 100% mortality of S. litura within 72-96 hours. Our results suggest that the use of both toxins as a gene pyramiding strategy to control both lepidopteran and hemipterans insects on commercial basis to reduce the use of chemical pesticides.

BvcZR3 and BvHs1pro-1 Genes Pyramiding Enhanced Beet Cyst Nematode (Heterodera schachtii Schm.) Resistance in Oilseed Rape (Brassica napus L.).

Beet cyst nematode (Heterodera schachtii Schm.) is one of the most damaging pests in sugar beet growing areas around the world. The Hs1pro-1 and cZR3 genes confer resistance to the beet cyst nematode, and both were cloned from sugar beet translocation line (A906001). The translocation line carried the locus from B. procumbens chromosome 1 including Hs1pro-1 gene and resistance gene analogs (RGA), which confer resistance to Heterodera schachtii. In this research, BvHs1pro-1 and BvcZR3 genes were transferred into oilseed rape to obtain different transgenic lines by A. tumefaciens mediated transformation method. The cZR3Hs1pro-1 gene was pyramided into the same plants by crossing homozygous cZR3 and Hs1pro-1 plants to identify the function and interaction of cZR3 and Hs1pro-1 genes. In vitro and in vivo cyst nematode resistance tests showed that cZR3 and Hs1pro-1 plants could be infested by beet cyst nematode (BCN) juveniles, however a large fraction of penetrated nematode juveniles was not able to develop normally and stagnated in roots of transgenic plants, consequently resulting in a significant reduction in the number of developed nematode females. A higher efficiency in inhibition of nematode females was observed in plants expressing pyramiding genes than in those only expressing a single gene. Molecular analysis demonstrated that BvHs1pro-1 and BvcZR3 gene expressions in oilseed rape constitutively activated transcription of plant-defense related genes such as NPR1 (non-expresser of PR1), SGT1b (enhanced disease resistance 1) and RAR1 (suppressor of the G2 allele of skp1). Transcript of NPR1 gene in transgenic cZR3 and Hs1pro-1 plants were slightly up-regulated, while its expression was considerably enhanced in cZR3Hs1pro-1 gene pyramiding plants. The expression of EDS1 gene did not change significantly among transgenic cZR3, Hs1pro-1 and cZR3Hs1pro-1 gene pyramiding plants and wild type. The expression of SGT1b gene was slightly up-regulated in transgenic cZR3 and Hs1pro-1 plants compared with the wild type, however, its expression was not changed in cZR3Hs1pro-1 gene pyramiding plant and had no interaction effect. RAR1 gene expression was significantly up-regulated in transgenic cZR3 and cZR3Hs1pro-1 genes pyramiding plants, but almost no expression was found in Hs1pro-1 transgenic plants. These results show that nematode resistance genes from sugar beet were functional in oilseed rape and conferred BCN resistance by activation of a CC-NBS-LRR R gene mediated resistance response. The gene pyramiding had enhanced resistance, thus offering a novel approach for the BCN control by preventing the propagation of BCN in oilseed rape. The transgenic oilseed rape could be used as a trap crop to offer an alternative method for beet cyst nematode control.

Owlet moths (Lepidoptera: Noctuoidea) associated with Bt and non- Bt soybean in the brazilian savanna / Noctuóides (Lepidoptera: Noctuoidea) associados a soja Bt e não-Bt no Cerrado brasileiro

Abstract The use of GMO expressing Bt toxin in soybean production has increased significantly in the last years in Brazil in order to manage the damage caused by lepidopteran pests. In this study, we compared the richness and abundance of owlet moths (Noctuoidea) associated with Bt and non-Bt soybean. We determined the temporal variations as a function of phenology, and correlated the population variations of the most common species with meteorological variables. The research was conducted at the experimental area of Embrapa Cerrados. The collection method used was differentiated being suppressive and absolute. A total of 13 species were collected, of which eight occurred on Bt soybeans. The most representative taxa were Chrysodeixis includens (72.87%), Anticarsia gemmatalis (18.17%) and Spodoptera spp (5.22%). The number of larvae belonging to species targeted by the Bt technology was 10 times lower on Bt than on non-Bt soybeans. Utetheisa ornatrix and Elaphria deltoides were recorded on soybean for the first time, observing larvae of both species in non-Bt soybean and those of U. ornatrix also in Bt soybean. Only A. gemmatalis larvae correlated (p <0.05) negatively with precipitation. This study provided field information on the abundance and species richness of owlet moths on non-Bt soybeans, associated with the effects of Bt soybean. When considering the different levels of infestation between cultivars as a criterion, larvae monitoring is of substantial importance in order to develop the lost control program.

Resumo O uso de OGM que expressam toxina Bt na produção de soja tem aumentado significativamente nos últimos anos no Brasil e são utilizados para conter os danos causados ​​pelos lepidópteros pragas. Neste estudo comparamos a riqueza e a abundância de Noctuoides (Noctuoidea) associados à soja Bt e não-Bt. Determinamos as variações temporais em função da fenologia e correlacionamos às variações populacionais das espécies mais comuns com variáveis ​​meteorológicas. A pesquisa foi conduzida na área experimental da Embrapa Cerrados. O método de coleta utilizado foi diferenciado sendo supressivo e absoluto. Um total de 13 espécies foram coletadas, das quais oito ocorreram em soja Bt. Os taxa mais representativos foram Chrysodeixis includens, Anticarsia gemmatalis e Spodoptera spp. O número de larvas pertencentes às espécies alvo da tecnologia Bt foram 10 vezes menores na soja Bt do que em soja não-Bt . Utetheisa ornatrix e Elaphria deltoides foram registradas na soja pela primeira vez, observando-se larvas de ambas espécies na soja não-Bt e as de U. ornatrix também na soja Bt. Somente as larvas de A. gemmatalis se correlacionaram (p <0,05) negativamente com a precipitação. Este estudo forneceu informações em campo sobre a abundância e riqueza de espécies na soja não- Bt, associada aos efeitos da soja Bt. A importância do monitoramento das lagartas é substancial, a fim de tomar a melhor decisão de controle, considerando-se os diferentes níveis de infestação entre cultivares como critério.

Production of santalenes and bergamotene in Nicotiana tabacum plants.

Terpenes play an important role in plant-insect relationships, and these relationships can potentially be modified by altering the profile of terpenes emitted from plants using metabolic engineering methods. Transgenic plants generated by employing such methods offer the prospect of low-cost sustainable pest management; in this regard, we used chloroplast targeting and cytosolic mevalonic acid pathway enhancement in this study to investigate the interaction of santalenes and bergamotene with insects. The santalene- and bergamotene-emitting transgenic tobacco plants thus generated were utilized to study host preference in the green peach aphid (Myzus persicae (Sulzer)). The results showed that co-expression of either 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) or truncated HMGR with santalene synthase led to the production of higher amounts of santalenes and bergamotene in transgenic tobacco plants, and that these santalene- and bergamotene-emitting plants were attractive to green peach aphids. We accordingly propose that such transgenic plants may have potential application in pest management as a trap crop to prevent green peach aphid infestation of wild-type tobacco plants.

Over-expression of the red plant gene R1 enhances anthocyanin production and resistance to bollworm and spider mite in cotton.

Anthocyanins are a class of pigments ubiquitously distributed in plants and play roles in adoption to several stresses. The red plant gene (R1) promotes light-induced anthocyanin accumulation and red/purple pigmentation in cotton. Using 11 markers developed via genome resequencing, the R1 gene was located in an interval of approximately 136 kb containing three annotated genes. Among them, a PAP1 homolog, GhPAP1D (Gohir.D07G082100) displayed differential transcript level in the red- and green-plant leaves. GhPAP1D encoded a R2R3-MYB transcription factor and its over-expression resulted in increased anthocyanin accumulation in transgenic tobaccos and cottons. Dual luciferase assay indicated that GhPAP1D activated the promoters of several cotton anthocyanin structural genes in tobacco leaves. Importantly, we found that the GhPAP1D-overexpressing cotton leaves had increased resistance to both bollworm and spite mite. Our data demonstrated that GhPAP1D was the controlling gene of the red plant phenotype in cotton, and as the major anthocyanin regulator, this gene was potential to create transgenic cottons with resistance to a broad spectrum of herbivores.

Identification of target genes for RNAi-mediated control of the Twospotted Spider Mite.

RNA interference (RNAi) is being developed for the management of pests that destroy crops. The twospotted Spider Mite (TSSM), Tetranychus urticae is a worldwide pest due to its unique physiological and behavioral characteristics including extraordinary ability to detoxify a wide range of pesticides and feed on many host plants. In this study, we conducted experiments to identify target genes that could be used for the development of RNAi-based methods to control TSSM. Leaf disc feeding assays revealed that knockdown in the expression genes coding for proteins involved in the biosynthesis and action of juvenile hormone (JH) and action of ecdysteroids [Methoprene-tolerant (Met), retinoid X receptor ß, farnesoic acid O-methyltransferase, and CREB-binding protein] caused 35-56% mortality. Transgenic tobacco plants expressing hairpin dsRNA targeting Met gene were generated and tested. About 48% mortality was observed in TSSM raised on transgenic tobacco plants expressing dsMet. These studies not only broaden our knowledge on understanding hormone action in TSSM but also identified target genes that could be used in RNAi-mediated control of TSSM.