An ABA-serotonin module regulates root suberization and salinity tolerance

Suberin in roots acts as a physical barrier preventing water/mineral losses. In Arabidopsis, root suberization is regulated by abscisic acid (ABA) and ethylene in response to nutrient stresses. ABA also mediates coordination between microbiota and root endodermis in mineral nutrient homeostasis. However, it is not known whether this regulatory system is common to plants in general, and whether there are other key molecule(s) involved. We show that serotonin acts downstream of ABA in regulating suberization in rice and Arabidopsis and negatively regulates suberization in rice roots in response to salinity. We show that ABA represses transcription of the key gene (OsT5H) in serotonin biosynthesis, thus promoting root suberization in rice. Conversely, overexpression of OsT5H or supplementation with exogenous serotonin represses suberization and reduces tolerance to salt stress. These results identify an ABA-serotonin regulatory module controlling root suberization in rice and Arabidopsis, which is likely to represent a general mechanism as ABA and serotonin are ubiquitous in plants. These findings are of significant importance to breeding novel crop varieties that are resilient to abiotic stresses and developing strategies for production of suberin-rich roots to sequestrate more CO₂ , helping to mitigate the effects of climate change.

Virus-induced plant volatiles mediate the olfactory behaviour of its insect vectors

Plant viruses can manipulate their hosts to release odours that are attractive or repellent to their insect vectors. However, the volatile organic compounds (VOCs), either individually or as mixtures, which play a key role in the olfactory behaviour of insect vectors remains largely unknown. Our study focused on green rice leafhoppers (GRLHs) vectoring rice dwarf virus (RDV) revealed that RDV infection significantly induced the emission of (E)-β-caryophyllene and 2-heptanol by rice plants, which influenced the olfactory behaviour of both non-viruliferous and viruliferous GRLHs. (E)-β-caryophyllene attracted non-viruliferous GRLHs to settle on RDV-infected plants, but neither attracted nor repelled viruliferous GRLHs. In contrast, 2-heptanol repelled viruliferous GRLHs to settle on RDV-infected plants, but neither repelled nor attracted non-viruliferous GRLHs. Suppression of (E)-β-caryophyllene synthase OsCAS via CRISPR-Cas9 to generate oscas-1 plants enabled us to confirm the important role played by (E)-β-caryophyllene in modulating the virus-vector-host plant interaction. These novel results reveal the role of these virus-induced VOCs in modulating the behaviour of its GRLH insect vector and may facilitate the design of new strategies for disease control through manipulation of plant volatile emissions.

pCAT vectors overcome inefficient electroporation of Cupriavidus necator H16

Cupriavidus necator H16 is a chemolithoautotroph with a range of industrial biotechnological applications. Advanced metabolic engineering in the bacterium, however, is impeded by low transformation efficiency, making it difficult to introduce and screen new genetic functions rapidly. This study systematically characterized the broad host range plasmids pBHR1, pBBR1MCS-2 and pKT230 used frequently for C. necator engineering. Kanamycin resistance cassette (KanR) and a truncated sequence of the replication origin (Rep) are contributing factors to C. necator low electroporation transformation efficiency. Consequently, a series of modular minimal plasmids, named pCAT, were constructed. pCAT vectors transform C. necator H16 with a > 3000-fold higher efficiency (up to 10⁷ CFU/μg DNA) compared to control plasmids. Further, pCAT vectors are highly stable, expressing reporter proteins over several days of serial cultivation in the absence of selection pressure. Finally, they can be assembled rapidly from PCR or synthesized DNA fragments, and restriction-ligation reactions can be efficiently electroporated directly into C. necator, circumventing the requirement to use Escherichia coli for plasmid maintenance or propagation. This study demonstrates that an understanding of the behaviour of the constituent parts of plasmids in a host is key to efficient propagation of genetic information, while offering new methods for engineering a bacterium with desirable industrial biotechnological features.

The Impact of Environmental Stress on Bt Crop Performance

Bt crops have been grown commercially for more than two decades. They have proven remarkably effective in the control of target insect pests. However, Bt crops can become less effective under various forms of environmental stress. Most studies in this area have considered the effect of environmental stress on Bt insecticidal protein levels or target pest mortality, but not both, resulting in a lack of mechanistic analysis. In this review, we critically examine previous research addressing the impact of environmental stress on the effectiveness of Bt crops. We find that the body of research data is not sufficiently robust to allow the reliable prediction of the performance of Bt crops under extreme climatic conditions.

A proteomic-based approach to study underlying molecular responses of the small intestine of Wistar rats to genetically modified corn (MON810)

A genetically modified (GM) commercial corn variety, MON810, resistant to European corn borer, has been shown to be non-toxic to mammals in a number of rodent feeding studies carried out in accordance with OECD Guidelines. Insect resistance results from expression of the Cry1Ab gene encoding an insecticidal Bt protein that causes lysis and cell death in susceptible insect larvae by binding to midgut epithelial cells, which is a key determinant of Cry toxin species specificity. Whilst whole animal studies are still recognised as the 'gold standard' for safety assessment, they only provide indirect evidence for changes at the cellular/organ/tissue level. In contrast, omics-based technologies enable mechanistic understanding of toxicological or nutritional events at the cellular/receptor level. To address this important knowledge-gap and to gain insights into the underlying molecular responses in rat to MON810, differential gene expression in the epithelial cells of the small intestine of rats fed formulated diets containing MON810, its near isogenic line, two conventional corn varieties, and a commercial (Purina™) corn-based control diet were investigated using comparative proteomic profiling. Pairwise and five-way comparisons showed that the majority of proteins that were differentially expressed in the small intestine epithelial cells in response to consumption of the different diets in both 7-day and 28-day studies were related to lipid and carbohydrate metabolism and protein biosynthesis. Irrespective of the diet, a limited number of stress-related proteins were shown to be differentially expressed. However these stress-related proteins differed between diets. No adverse clinical or behavioural effects, or biomarkers of adverse health, were observed in rats fed GM corn compared to the other corn diets. These findings suggest that MON810 has negligible effects on the small intestine of rats at the cellular level compared with the well-documented toxicity observed in susceptible insects.

Evolution of Asian Corn Borer Resistance to Bt Toxins Used Singly or in Pairs

Transgenic crops producing insecticidal proteins from Bacillus thuringiensis (Bt) have revolutionized pest control, but the benefits of this approach have been reduced by the evolution of resistance in pests. The widely adopted 'pyramid strategy' for delaying resistance entails transgenic crops producing two or more distinct toxins that kill the same pest. The limited experimental evidence supporting this strategy comes primarily from a model system under ideal conditions. Here we tested the pyramid strategy under nearly worst-case conditions, including some cross-resistance between the toxins in the pyramid. In a laboratory selection experiment with an artificial diet, we used Bt toxins Cry1Ab, Cry1F, and Cry1Ie singly or in pairs against Ostrinia furnacalis, one of the most destructive pests of corn in Asia. Under the conditions evaluated, pairs of toxins did not consistently delay the evolution of resistance relative to single toxins.

Companion planting with French marigolds protects tomato plants from glasshouse whiteflies through the emission of airborne limonene

Horticulturalists and gardeners in temperate regions often claim that planting marigolds next to tomato plants protects the tomatoes from the glasshouse whitefly (Trialeurodes vaporariorum Westwood). If shown to hold true, this technique could be used in larger-scale tomato production, protecting the crop and helping to introduce greater plant diversity into these agro-ecosystems. Here we present two large-scale glasshouse trials corresponding to the two main ways growers are likely to use marigolds to control whiteflies. In the first, marigolds are grown next to tomato throughout the growing period and we quantify whitefly population growth from the seedling stage over a 48 day infestation period. Here we show that association with marigolds significantly slows whitefly population development. Introducing additional whitefly-attractive 'pull' plants around the perimeter of plots has little effect, but reducing the proportion of marigolds and introducing other non-hosts of whiteflies (basil, nasturtium and Chinese cabbage) also reduces whitefly populations on tomato. The second experiment assesses the efficacy of marigolds when used as an 'emergency' measure. Here we allow whitefly populations to build to a high density on unprotected tomatoes then introduce marigolds and assess whitefly population over a further period. Following laboratory work showing limonene to be a major chemical component of French marigolds and a negative behaviour response of whiteflies to this compound, limonene dispensers are added as an additional treatment to this experiment. "Emergency" marigold companion planting yielded minimal reductions in whitefly performance, but the use of limonene dispensers was more effective. Our work indicates that companion planting short vine tomatoes with French marigolds throughout the growing season will slow development of whitefly populations. Introducing marigolds to unprotected tomatoes after significant whitefly build-up will be less effective. The use of limonene dispensers placed near to tomato plants also shows promise. It is argued that this work supports the possibility of the development of a mixture of tomato companion plants that infer 'associational resistance' against many major invertebrate pests of tomato. Such a mixture, if comprising edible or ornamental plants, would be economically viable, would reduce the need for additional chemical and biological control, and, if used outdoors, would generate plant-diverse agro-ecosystems that are better able to harbour invertebrate wildlife.

Resistance of rice to insect pests mediated by suppression of serotonin biosynthesis

Rice is one of the world's most important foods, but its production suffers from insect pests, causing losses of billions of dollars, and extensive use of environmentally damaging pesticides for their control^1,2. However, the molecular mechanisms of insect resistance remain elusive. Although a few resistance genes for planthopper have been cloned, no rice germplasm is resistant to stem borers. Here, we report that biosynthesis of serotonin, a neurotransmitter in mammals³, is induced by insect infestation in rice, and its suppression confers resistance to planthoppers and stem borers, the two most destructive pests of rice². Serotonin and salicylic acid derive from chorismate⁴. In rice, the cytochrome P450 gene CYP71A1 encodes tryptamine 5-hydroxylase, which catalyses conversion of tryptamine to serotonin⁵. In susceptible wild-type rice, planthopper feeding induces biosynthesis of serotonin and salicylic acid, whereas in mutants with an inactivated CYP71A1 gene, no serotonin is produced, salicylic acid levels are higher and plants are more insect resistant. The addition of serotonin to the resistant rice mutant and other brown planthopper-resistant genotypes results in a loss of insect resistance. Similarly, serotonin supplementation in artificial diet enhances the performance of both insects. These insights demonstrate that regulation of serotonin biosynthesis plays an important role in defence, and may prove valuable for breeding insect-resistant cultivars of rice and other cereal crops.

RNAi-mediated gene silencing in Rhynchophorus ferrugineus (Oliver) (Coleoptera: Curculionidae)

RNA interference (RNAi) is a powerful strategy for gene function analysis, and it is also widely studied in view of a promising use in pest control. The red palm weevil, Rhynchophorus ferrugineus (Oliver) (Coleoptera: Curculionidae), is one of the most devastating pests of palm in the world. Conventional pest management practices are not adequate to control this insect, thus the development of efficient approaches with minimal environmental impact are needed. In this work, the potential of RNAi in R. ferrugineus has been investigated through the silencing of three different genes (α-amylase, V-ATPase, Ecdysone receptor). For each gene we tested two different doses (1,500 and 5,500 ng) and two delivery techniques (injection and ingestion), evaluating both gene knockdown and mortality on insects. Results show that RNAi mediated gene silencing in R. ferrugineus varies from gene to gene, and that the response is dose-dependent, with stronger effects when dsRNA was administered by injection. In parallel, the same study was carried out with the model organism Tribolium castaneum Herbst (Coleoptera: Tenebrionidae), with results showing a different pattern of response, although the two insects belong to the same order.

RNAi-mediated knockdown of the voltage gated sodium ion channel TcNav causes mortality in Tribolium castaneum

The voltage-gated sodium ion channel (VGSC) belongs to the largest superfamily of ion channels. Since VGSCs play key roles in physiological processes they are major targets for effective insecticides. RNA interference (RNAi) is widely used to analyse gene function, but recently, it has shown potential to contribute to novel strategies for selectively controlling agricultural insect pests. The current study evaluates the delivery of dsRNA targeted to the sodium ion channel paralytic A (TcNav) gene in Tribolium castaneum as a viable means of controlling this insect pest. Delivery of TcNav dsRNA caused severe developmental arrest with larval mortalities up to 73% post injection of dsRNA. Injected larvae showed significant (p < 0.05) knockdown in gene expression between 30-60%. Expression was also significantly (p < 0.05) reduced in pupae following injection causing 30% and 42% knockdown for early and late pupal stages, respectively. Oral delivery of dsRNA caused dose-dependant mortalities of between 19 and 51.34%; this was accompanied by significant (p < 0.05) knockdown in gene expression following 3 days of continuous feeding. The majority of larvae injected with, or fed, dsRNA died during the final larval stage prior to pupation. This work provides evidence of a viable RNAi-based strategy for insect control.

Novel resistance mechanisms of a wild tomato against the glasshouse whitefly

The glasshouse whitefly, Trialeurodes vaporariorum, is an important pest of many crop plants including tomato, Solanum lycopersicum. Many wild tomato species exhibit a higher resistance to whiteflies. Therefore, locating the source of this enhanced resistance and breeding it into commercial tomato species is an important strategy to reduce the impact of pests on crops. Here, we assessed the pest resistance of Lycopersicon pimpinellifolium by comparing oviposition and feeding data from T. vaporariorum on this wild tomato species with data collected from a susceptible commercial tomato, S. lycopersicum var. 'Elegance'. The location of resistance factors was examined by use of electrical penetration graph (EPG) studies on these tomato species. Results show that whiteflies preferentially settled on the commercial tomato more often in 80 % of the replicates when given free choice between the two tomato species and laid significantly fewer eggs on L. pimpinellifolium. Whiteflies exhibited a shorter duration of the second feeding bout, reduced pathway phase probing, longer salivation in the phloem and more non-probing activities in the early stages of the EPG on the wild tomato species compared to the commercial tomato. These findings evidence that a dual mode of resistance is present in this wild tomato against T. vaporariorum: a post-penetration, pre-phloem resistance mechanism and a phloem-located factor, which to the best of our knowledge is the first time that evidence for this has been presented. These findings can be used to inform future breeding strategies to increase the resistance of commercial tomato varieties against this important pest.

Proteomic analysis shows that stress response proteins are significantly up-regulated in resistant diploid wheat (Triticum monococcum) in response to attack by the grain aphid (Sitobion avenae)

The grain aphid Sitobion avenae (F.) is a major pest of wheat, acting as a virus vector as well as causing direct plant damage. Commonly grown wheat varieties in the UK have only limited resistance to this pest. The present study was carried out to investigate the potential of a diploid wheat line (ACC20 PGR1755), reported as exhibiting resistance to S. avenae, to serve as a source of resistance genes. The diploid wheat line was confirmed as partially resistant, substantially reducing the fecundity, longevity and growth rate of the aphid. Proteomic analysis showed that approximately 200 protein spots were reproducibly detected in leaf extracts from both the resistant line and a comparable susceptible line (ACC5 PGR1735) using two-dimensional gel electrophoresis and image comparison software. Twenty-four spots were significantly up-regulated (>2-fold) in the resistant line after 24 h of aphid feeding (13 and 11 involved in local and systemic responses, respectively). Approximately 50 % of all differentially expressed protein spots were identified by a combination of database searching with MS and MS/MS data, revealing that the majority of proteins up-regulated by aphid infestation were involved in metabolic processes (including photosynthesis) and transcriptional regulation. However, in the resistant line only, several stress response proteins (including NBS-LRR-like proteins) and oxidative stress response proteins were identified as up-regulated in response to aphid feeding, as well as proteins involved in DNA synthesis/replication/repair. This study indicates that the resistant diploid line ACC20 PGR1755 may provide a valuable resource in breeding wheat for resistance to aphids.

Transgenic plants expressing ω-ACTX-Hv1a and snowdrop lectin (GNA) fusion protein show enhanced resistance to aphids

Recombinant fusion proteins containing arthropod toxins have been developed as a new class of biopesticides. The recombinant fusion protein Hv1a/GNA, containing the spider venom toxin ω-ACTX-Hv1a linked to snowdrop lectin (GNA) was shown to reduce survival of the peach-potato aphid Myzus persicae when delivered in artificial diet, with survival <10% after 8 days exposure to fusion protein at 1 mg/ml. Although the fusion protein was rapidly degraded by proteases in the insect, Hv1a/GNA oral toxicity to M. persicae was significantly greater than GNA alone. A construct encoding the fusion protein, including the GNA leader sequence, under control of the constitutive CaMV 35S promoter was transformed into Arabidopsis; the resulting plants contained intact fusion protein in leaf tissues at an estimated level of 25.6 ± 4.1 ng/mg FW. Transgenic Arabidopsis expressing Hv1a/GNA induced up to 40% mortality of M. persicae after 7 days exposure in detached leaf bioassays, demonstrating that transgenic plants can deliver fusion proteins to aphids. Grain aphids (Sitobion avenae) were more susceptible than M. persicae to the Hv1a/GNA fusion protein in artificial diet bioassays (LC50 = 0.73 mg/ml after 2 days against LC50 = 1.81 mg/ml for M. persicae), as they were not able to hydrolyze the fusion protein as readily as M. persicae. Expression of this fusion protein in suitable host plants for the grain aphid is likely to confer higher levels of resistance than that shown with the M. persicae/Arabidopsis model system.

Downregulation and mutation of a Cadherin gene associated with Cry1Ac resistance in the Asian Corn Borer, Ostrinia furnacalis (Guenée)

Development of resistance in target pests is a major threat to long-term use of transgenic crops expressing Bacillus thuringiensis (Bt) Cry toxins. To manage and/or delay the evolution of resistance in target insects through the implementation of effective strategies, it is essential to understand the basis of resistance. One of the most important mechanisms of insect resistance to Bt crops is the alteration of the interactions between Cry toxins and their receptors in the midgut. A Cry1Ac-selected strain of Asian corn borer (ACB), Ostrinia furnacalis, a key pest of maize in China, evolved three mutant alleles of a cadherin-like protein (OfCAD) (MPR-r1, MPR-r2 and MPR-r3), which mapped within the toxin-binding region (TBR). Each of the three mutant alleles possessed two or three amino acid substitutions in this region, especially Thr¹⁴⁵⁷→Ser. In highly resistant larvae (ACB-Ac200), MPR-r2 had a 26-amino acid residue deletion in the TBR, which resulted in reduced binding of Cry1Ac compared to the MPR from the susceptible strain, suggesting that the number of amino acid deletions influences the level of resistance. Furthermore, downregulation of OfCAD gene (ofcad) transcription was observed in the Cry1Ac resistant strain, ACB-Ac24, suggesting that Cry1Ac resistance in ACB is associated with the downregulation of the transcript levels of the cadherin-like protein gene. The OfCAD identified from ACB exhibited a high degree of similarity to other members of the cadherin super-family in lepidopteran species.

Inheritance patterns, dominance and cross-resistance of Cry1Ab- and Cry1Ac-selected Ostrinia furnacalis (Guenée)

Two colonies of Asian corn borer, Ostrinia furnacalis (Guenée), artificially selected from a Bt-susceptible colony (ACB-BtS) for resistance to Cry1Ab (ACB-AbR) and Cry1Ac (ACB-AcR) toxins, were used to analyze inheritance patterns of resistance to Cry1 toxins. ACB-AbR and ACB-AcR evolved significant levels of resistance, with resistance ratios (RR) of 39-fold and 78.8-fold to Cry1Ab and Cry1Ac, respectively. The susceptibility of ACB-AbR larvae to Cry1Ac and Cry1F toxins, which had not previously been exposed, were significantly reduced, being >113-fold and 48-fold, respectively. Similarly, susceptibility of ACB-AcR larvae to Cry1Ab and Cry1F were also significantly reduced (RR > nine-fold, RR > 18-fold, respectively), indicating cross-resistance among Cry1Ab, Cry1Ac, and Cry1F toxins. However, ACB-AbR and ACB-AcR larvae were equally susceptible to Cry1Ie as were ACB-BtS larvae, indicating no cross-resistance between Cry1Ie and Cry1Ab or Cry1Ac toxins; this may provide considerable benefits in preventing or delaying the evolution of resistance in ACB to Cry1Ab and Cry1Ac toxins. Backcrossing studies indicated that resistance to Cry1Ab toxin was polygenic in ACB-AbR, but monogenic in ACB-AcR, whilst resistance to Cry1Ac toxin was primarily monogenic in both ACB-AbR and ACB-AcR, but polygenic as resistance increased.

Novel biopesticide based on a spider venom peptide shows no adverse effects on honeybees

Evidence is accumulating that commonly used pesticides are linked to decline of pollinator populations; adverse effects of three neonicotinoids on bees have led to bans on their use across the European Union. Developing insecticides that pose negligible risks to beneficial organisms such as honeybees is desirable and timely. One strategy is to use recombinant fusion proteins containing neuroactive peptides/proteins linked to a 'carrier' protein that confers oral toxicity. Hv1a/GNA (Galanthus nivalis agglutinin), containing an insect-specific spider venom calcium channel blocker (ω-hexatoxin-Hv1a) linked to snowdrop lectin (GNA) as a 'carrier', is an effective oral biopesticide towards various insect pests. Effects of Hv1a/GNA towards a non-target species, Apis mellifera, were assessed through a thorough early-tier risk assessment. Following feeding, honeybees internalized Hv1a/GNA, which reached the brain within 1 h after exposure. However, survival was only slightly affected by ingestion (LD50>100 µg bee(-1)) or injection of fusion protein. Bees fed acute (100 µg bee(-1)) or chronic (0.35 mg ml(-1)) doses of Hv1a/GNA and trained in an olfactory learning task had similar rates of learning and memory to no-pesticide controls. Larvae were unaffected, being able to degrade Hv1a/GNA. These tests suggest that Hv1a/GNA is unlikely to cause detrimental effects on honeybees, indicating that atracotoxins targeting calcium channels are potential alternatives to conventional pesticides.

Modelling pathways to Rubisco degradation: a structural equation network modelling approach

'Omics analysis (transcriptomics, proteomics) quantifies changes in gene/protein expression, providing a snapshot of changes in biochemical pathways over time. Although tools such as modelling that are needed to investigate the relationships between genes/proteins already exist, they are rarely utilised. We consider the potential for using Structural Equation Modelling to investigate protein-protein interactions in a proposed Rubisco protein degradation pathway using previously published data from 2D electrophoresis and mass spectrometry proteome analysis. These informed the development of a prior model that hypothesised a pathway of Rubisco Large Subunit and Small Subunit degradation, producing both primary and secondary degradation products. While some of the putative pathways were confirmed by the modelling approach, the model also demonstrated features that had not been originally hypothesised. We used Bayesian analysis based on Markov Chain Monte Carlo simulation to generate output statistics suggesting that the model had replicated the variation in the observed data due to protein-protein interactions. This study represents an early step in the development of approaches that seek to enable the full utilisation of information regarding the dynamics of biochemical pathways contained within proteomics data. As these approaches gain attention, they will guide the design and conduct of experiments that enable 'Omics modelling to become a common place practice within molecular biology.

Insecticidal activity of wheat Hessian fly responsive proteins HFR-1 and HFR-3 towards a non-target wheat pest, cereal aphid (Sitobion avenae F.)

The interaction between Hessian fly (Mayetiola destructor) and wheat (Triticum aestivum) involves a gene-for-gene resistance mechanism. The incompatible interaction leading to resistance involves up-regulation of several Hfr (Hessian fly responsive) genes encoding proteins with potential insecticidal activity. The encoded proteins HFR-1, HFR-2 and HFR-3 all possess lectin-like domains. HFR-1 and HFR-3 were produced as recombinant proteins using Escherichia coli and Pichia pastoris, respectively as expression hosts. Purified recombinant proteins were assayed for insecticidal effects towards cereal aphid (Sitobion avenae), an insect to which wheat shows only tolerance. Both HFR-1 and HFR-3 were found to be insecticidal towards S. avenae when fed in artificial diet. Although HFR-3 has sequence similarity and similar chitin-binding activity to wheat germ agglutinin (WGA), the latter protein was almost non-toxic to S. avenae. HFR-3 binds strongly to aphid midguts after ingestion, whereas WGA binds but does not persist over a feed-chase period. Quantitative PCR showed that Hfr-3 mRNA does not increase in level after cereal aphid infestation. The results suggest that the lack of effective resistance to cereal aphid in wheat is not due to an absence of genes encoding suitable insecticidal proteins, but results from a failure to up-regulate gene expression in response to aphid attack.

Developmental studies of transgenic maize expressing Cry1Ab on the African stem borer, Busseola fusca; effects on midgut cellular structure

BACKGROUND

Busseola fusca is a major pest of maize in Africa but unfortunately is difficult to control using chemical insecticides. Insect-resistant transgenic crops may provide an alternative viable strategy to control this pest.

RESULTS

Recombinant Cry1Ab (1%) reduced larval weight by 60% over the trial period, while larval weight in the control group increased by 25%; no effects on mortality were observed. Insect survival, developmental rate and pupal and adult weight were significantly reduced (P < 0.05) on maize expressing Cry1Ab (MON810) compared with the non-transformed parental line. These differences were more pronounced with second-instar larvae than with third-instar larvae. Leaf area consumed by Bacillus thuringiensis (Bt)-fed larvae was significantly lower (0.5 cm(2) larva(-1) day(-1)) compared with the area consumed by control-fed insects (3.3 cm(2) larva(-1) day(-1)). EM studies revealed that consumption of Bt maize deleteriously affected gut integrity. Effects were observed in columnar cells of the midgut epithelium, with the cytoplasm becoming highly vacuolated; the microvilli were disorganised, the mitochondria were abnormal and there was an increase in the number of lysosomal bodies. The rough endoplasmic reticulum had also become dilated.

CONCLUSION

This study confirms the potential for Bt maize, when used as part of an IPM programme, for control of B. fusca.

Insect-resistant biotech crops and their impacts on beneficial arthropods

With a projected population of 10 billion by 2050, an immediate priority for agriculture is to achieve increased crop yields in a sustainable and cost-effective way. The concept of using a transgenic approach was realized in the mid-1990s with the commercial introduction of genetically modified (GM) crops. By 2010, the global value of the seed alone was US $11.2 billion, with commercial biotech maize, soya bean grain and cotton valued at approximately US $150 billion. In recent years, it has become evident that insect-resistant crops expressing δ-endotoxin genes from Bacillus thuringiensis have made a significant beneficial impact on global agriculture, not least in terms of pest reduction and improved quality. However, because of the potential for pest populations to evolve resistance, and owing to lack of effective control of homopteran pests, alternative strategies are being developed. Some of these are based on Bacillus spp. or other insect pathogens, while others are based on the use of plant- and animal-derived genes. However, if such approaches are to play a useful role in crop protection, it is desirable that they do not have a negative impact on beneficial organisms at higher trophic levels thus affecting the functioning of the agro-ecosystem. This widely held concern over the ecological impacts of GM crops has led to the extensive examination of the potential effects of a range of transgene proteins on non-target and beneficial insects. The findings to date with respect to both commercial and experimental GM crops expressing anti-insect genes are discussed here, with particular emphasis on insect predators and parasitoids.

Molecular interactions between wheat and cereal aphid (Sitobion avenae): analysis of changes to the wheat proteome

Aphids are major insect pests of cereal crops, acting as virus vectors as well as causing direct damage. The responses of wheat to infestation by cereal aphid (Sitobion avenae) were investigated in a proteomic analysis. Approximately, 500 protein spots were reproducibly detected in the extracts from leaves of wheat seedlings after extraction and 2-DE. Sixty-seven spots differed significantly between control and infested plants following 24 h of aphid feeding, with 27 and 11 up-regulated, and 8 and 21 down-regulated, in local or systemic tissues, respectively. After 8 days, 80 protein spots differed significantly between control and aphid treatments with 13 and 18 up-regulated and 27 and 22 down-regulated in local or systemic tissues, respectively. As positive controls, plants were treated with salicylic acid or methyl jasmonate; 81 and 37 differentially expressed protein spots, respectively, were identified for these treatments. Approximately, 50% of differentially expressed protein spots were identified by PMF, revealing that the majority of proteins altered by aphid infestation were involved in metabolic processes and photosynthesis. Other proteins identified were involved in signal transduction, stress and defence, antioxidant activity, regulatory processes, and hormone responses. Responses to aphid attack at the proteome level were broadly similar to basal non-specific defence and stress responses in wheat, with evidence of down-regulation of insect-specific defence mechanisms, in agreement with the observed lack of aphid resistance in commercial wheat lines.

Jatropha curcas oil body proteome and oleosins: L-form JcOle3 as a potential phylogenetic marker

The seed oil of Jatropha curcas has been proposed as a source of biodiesel. In plants, seed oil is stored in subcellular organelles called oil bodies (OBs), which are stabilized by proteins. Proteome composition of the J. curcas OBs revealed oleosins as the major component and additional proteins similar to those in other oil seed plants. Three J. curcas oleosins were isolated and characterized at the gene, transcript and protein level. They all contained the characteristic proline knot domain and were each present as a single copy in the genome. The smallest, L-form JcOle3 contained an intron. Isolation of its promoter revealed seed-specific cis-regulatory motifs among others. Spatio-temporal transcript expression of J. curcas oleosins was largely similar to that in other oil seed plants. Immunoassay with antibodies against an Arabidopsis oleosin or against JcOle3, on seed proteins extracted by different approaches, revealed JcOle3 oligomers. Alleles of JcOle3 and single nucleotide polymorphisms (SNPs) in its intron were identified in J. curcas accessions, species and hybrids. Identified alleles and SNPs could serve as markers in phylogenetic or breeding studies.