Characterization and expression analysis of a gene encoding a secreted lipase-like protein expressed in the salivary glands of the larval Hessian fly, Mayetiola destructor (Say)

Identification of salivary proteins of the cowpea aphid Aphis craccivora by transcriptome and LC-MS/MS analyses

Aphid salivary proteins mediate the interaction between aphids and their host plants. Moreover, these proteins facilitate digestion, detoxification of secondary metabolites, as well as activation and suppression of plant defenses. The cowpea aphid, Aphis craccivora, is an important sucking pest of leguminous crops worldwide. Although aphid saliva plays an important role in aphid plant interactions, knowledge of the cowpea aphid salivary proteins is limited. In this study, we performed transcriptomic and LC-MS/MS analyses to identify the proteins present in the salivary glands and saliva of A. craccivora. A total of 1,08,275 assembled transcripts were identified in the salivary glands of aphids. Of all these assembled transcripts, 53,714 (49.11%) and 53,577 (49.48%) transcripts showed high similarity to known proteins in the Nr and UniProt databases, respectively. A total of 2159 proteins were predicted as secretory proteins from the salivary gland transcriptome dataset, which contain digestive enzymes, detoxification enzymes, previously known effectors and elicitors, and potential proteins whose functions have yet to be determined. The proteomic analysis of aphid saliva resulted in the identification of 171 proteins. Tissue-specific expression of selected genes using RT-PCR showed that three genes were expressed only in the salivary glands. Overall, our results provide a comprehensive repertoire of cowpea aphid salivary proteins from the salivary gland and saliva, which will be a good resource for future effector functional studies and might also be useful for sustainable aphid management.

Comparative Hessian Fly Larval Transcriptomics Provides Novel Insight into Host and Nonhost Resistance

The Hessian fly is a destructive pest of wheat. Employing additional molecular strategies can complement wheat's native insect resistance. However, this requires functional characterization of Hessian-fly-responsive genes, which is challenging because of wheat genome complexity. The diploid Brachypodium distachyon (Bd) exhibits nonhost resistance to Hessian fly and displays phenotypic/molecular responses intermediate between resistant and susceptible host wheat, offering a surrogate genome for gene characterization. Here, we compared the transcriptomes of Biotype L larvae residing on resistant/susceptible wheat, and nonhost Bd plants. Larvae from susceptible wheat and nonhost Bd plants revealed similar molecular responses that were distinct from avirulent larval responses on resistant wheat. Secreted salivary gland proteins were strongly up-regulated in all larvae. Genes from various biological pathways and molecular processes were up-regulated in larvae from both susceptible wheat and nonhost Bd plants. However, Bd larval expression levels were intermediate between larvae from susceptible and resistant wheat. Most genes were down-regulated or unchanged in avirulent larvae, correlating with their inability to establish feeding sites and dying within 4-5 days after egg-hatch. Decreased gene expression in Bd larvae, compared to ones on susceptible wheat, potentially led to developmentally delayed 2nd-instars, followed by eventually succumbing to nonhost resistance defense mechanisms.

Structural and Nutritional Peculiarities Related to Lifespan Differences on Four Lopesia Induced Bivalve-Shaped Galls on the Single Super-Host Mimosa gemmulata

Super-host plants are elegant models to evaluate the peculiarities of gall structural and nutritional profiles due to the stimuli of distinct gall inducers in temporal and spatial perspectives. Galls induced by congeneric insects, Lopesia spp. (Diptera, Cecidomyiidae) on the same host plant, Mimosa gemmulata Barneby (Fabaceae) were analyzed to estimate if variations of 1 or 2 months in gall lifespans may result in differences over the accumulation of nutritional resources, and their compartmentalization both in cell walls and protoplasm. Mimosa gemmulata hosts four Lopesia-induced galls: the lenticular bivalve-shaped gall (LG) with a 2-month life cycle, the brown lanceolate bivalve-shaped gall (BLG) and the green lanceolate bivalve-shaped gall (GLG) with 3 month-life cycles, and the globoid bivalve-shaped gall (GG) with a 4 month-life cycle. The comparisons among the four Lopesia galls, using anatomical, histometric, histochemical, and immunocytochemical tools, have demonstrated that the longest lifespan of the GG related to its highest increment in structural and nutritional traits compared with the LG, GLG, and BLG. The differences among the tissue stratification and cell wall thickness of the galls with the 2-month and the 3-month lifespans were subtle. However, the GG had thicker cell walls and higher stratification of the common storage tissue, schlerenchymatic layers and typical nutritive tissue than the other three gall morphospecies. The higher tissue thickness of the GG was followed by the formation of a bidirectional gradient of carbohydrates in the protoplasm, and the detection of xyloglucans in cell walls. Current data supported the presumption that the longest the lifespan, the highest the impact over the structural and nutritional metabolism of the Lopesia galls associated to M. gemmulata.

In silico identification of effector proteins from generalist herbivore Spodoptera litura

BACKGROUND

The common cutworm, Spodoptera litura Fabricius is a leaf and fruit feeding generalist insect of the order Lepidoptera and a destructive agriculture pest. The broad host range of the herbivore is due to its ability to downregulate plant defense across different plants. The identity of Spodoptera litura released effectors that downregulate plant defense are largely unknown. The current study aims to identify genes encoding effector proteins from salivary glands of S. litura (Fab.).

RESULTS

Head and salivary glands of Spodoptera litura were used for de-novo transcriptome analysis and effector prediction. Eight hundred ninety-nine proteins from the head and 330 from salivary gland were identified as secretory proteins. Eight hundred eight proteins from the head and 267 from salivary gland proteins were predicted to be potential effector proteins.

CONCLUSIONS

This study is the first report on identification of potential effectors from Spodoptera litura salivary glands.

Australian sugarcane soldier fly's salivary gland transcriptome in response to starvation and feeding on sugarcane crops

The soldier fly is an endemic pest of sugarcane in Australia. Small numbers of larvae can cause significant damage to roots and reduce the crop yields. Little is known about the composition and function of the soldier fly salivary gland, its secretions, and their roles in insect-plant interactions. In this study, we performed transcriptome analysis of the salivary glands of starved and sugarcane root-fed soldier fly larvae. A total of 31 119 highly expressed assembled contigs were identified in the salivary glands and almost 50% of them showed high levels of similarity to known proteins in Nr databases. Of all the obtained contigs, only 9727 sequences contain an open reading frame of over 100 amino acids. Around 31% of contigs were predicted to encode secretory proteins, including some digestive and detoxifying enzymes and potential effectors. Some known salivary secreted peptides such as serine protease, cysteine proteinase inhibitors, antimicrobial peptides and venom proteins were among the top 100 highly expressed genes. Differential gene expression analysis revealed significant modulation of 850 transcripts in salivary glands upon exposure to plant roots or starvation stress. Here, we identified some venom proteins which were significantly upregulated in the salivary glands of soldier fly larvae exposed to sugarcane roots. In other insects and nematodes some of these proteins have been used to manipulate host plant defense systems and facilitate the invasion of the host plant. These findings provide a further insight into the identification of potential effector proteins involved in soldier fly-sugarcane interactions.

Intraspecific differences in plant defense induction by fall armyworm strains

The underlying adaptive mechanisms by which insect strains are associated with specific plants are largely unknown. In this study, we investigated the role of herbivore-induced defenses in the host plant association of fall armyworm (Spodoptera frugiperda) strains. We tested the expression of herbivore-induced defense-related genes and the activity of plant-defensive proteins in maize and Bermuda grass upon feeding by fall armyworm strains. The rice strain caterpillars induced greater accumulation of proteinase inhibitors in maize than the corn strain caterpillars. In Bermuda grass, feeding by the corn strain suppressed induction of trypsin inhibitor activity whereas the rice strain induced greater activity levels. Differences in elicitation of these plant defenses by the two strains seems to be due to differences in the activity levels of the salivary enzyme phospholipase C. The levels of plant defense responses were negatively correlated with caterpillar growth, indicating a fitness effect. Our results indicate that specific elicitors in the saliva of fall armyworm stains trigger differential levels of plant defense responses that affect caterpillar growth and thus may influence host plant associations in field conditions. The composition and secretion of plant defense elicitors may have a strong influence in the host plant association of insect herbivores.

Transcriptome analysis of the salivary glands of the grain aphid, Sitobion avenae

Aphid saliva plays important roles in aphid-host interactions, such as assisting aphid digestion, detoxification, activating or suppressing plant defenses. The grain aphid, Sitobion avenae, is one of the most devastating pests of cereals worldwide. In this study, we performed the transcriptome analysis of salivary glands of S. avenae. A total of 33,079 assembled unigenes were identified in the salivary glands of aphids. Of the all obtained unigenes, 15,833(47.86%) and 10,829(32.73%) unigenes showed high similarity to known proteins in Nr and Swiss-Prot databases respectively. 526 unigenes were predicted to encode secretory proteins, including some digestive and detoxifying enzymes and potential effectors. The RT-PCR and RT-qPCR results showed that all of the 15 most highly expressed putative secretory proteins specifically expressed in salivary glands. Interestingly, 11 of the 15 most highly expressed putative secretory proteins were still not matched to function-known proteins. We also detected the expression of 9 interested putative secretory proteins in aphid different tissues, including some digestive and detoxifying enzymes, effectors and Ca2+ binding proteins. The results showed that only glutathione-S-transferase 1 was specifically expressed in salivary glands. These findings provide a further insight into the identification of potential effectors involving in aphid-cereals interactions.

Gene Duplication and Gene Expression Changes Play a Role in the Evolution of Candidate Pollen Feeding Genes in Heliconius Butterflies

Heliconius possess a unique ability among butterflies to feed on pollen. Pollen feeding significantly extends their lifespan, and is thought to have been important to the diversification of the genus. We used RNA sequencing to examine feeding-related gene expression in the mouthparts of four species of Heliconius and one nonpollen feeding species, Eueides isabella. We hypothesized that genes involved in morphology and protein metabolism might be upregulated in Heliconius because they have longer proboscides than Eueides, and because pollen contains more protein than nectar. Using de novo transcriptome assemblies, we tested these hypotheses by comparing gene expression in mouthparts against antennae and legs. We first looked for genes upregulated in mouthparts across all five species and discovered several hundred genes, many of which had functional annotations involving metabolism of proteins (cocoonase), lipids, and carbohydrates. We then looked specifically within Heliconius where we found eleven common upregulated genes with roles in morphology (CPR cuticle proteins), behavior (takeout-like), and metabolism (luciferase-like). Closer examination of these candidates revealed that cocoonase underwent several duplications along the lineage leading to heliconiine butterflies, including two Heliconius-specific duplications. Luciferase-like genes also underwent duplication within lepidopterans, and upregulation in Heliconius mouthparts. Reverse-transcription PCR confirmed that three cocoonases, a peptidase, and one luciferase-like gene are expressed in the proboscis with little to no expression in labial palps and salivary glands. Our results suggest pollen feeding, like other dietary specializations, was likely facilitated by adaptive expansions of preexisting genes—and that the butterfly proboscis is involved in digestive enzyme production.

Insect-induced effects on plants and possible effectors used by galling and leaf-mining insects to manipulate their host-plant

Gall-inducing insects are iconic examples in the manipulation and reprogramming of plant development, inducing spectacular morphological and physiological changes of host-plant tissues within which the insect feeds and grows. Despite decades of research, effectors involved in gall induction and basic mechanisms of gall formation remain unknown. Recent research suggests that some aspects of the plant manipulation shown by gall-inducers may be shared with other insect herbivorous life histories. Here, we illustrate similarities and contrasts by reviewing current knowledge of metabolic and morphological effects induced on plants by gall-inducing and leaf-mining insects, and ask whether leaf-miners can also be considered to be plant reprogrammers. We review key plant functions targeted by various plant reprogrammers, including plant-manipulating insects and nematodes, and functionally characterize insect herbivore-derived effectors to provide a broader understanding of possible mechanisms used in host-plant manipulation. Consequences of plant reprogramming in terms of ecology, coevolution and diversification of plant-manipulating insects are also discussed.

Identification of Genes Potentially Responsible for extra-Oral Digestion and Overcoming Plant Defense from Salivary Glands of the Tarnished Plant Bug (Hemiptera: Miridae) Using cDNA Sequencing

Saliva is known to play a crucial role in tarnished plant bug (TPB, Lygus lineolaris [Palisot de Beauvois]) feeding. By facilitating the piercing, the enzyme-rich saliva may be used for extra-oral digestion and for overcoming plant defense before the plant fluids are ingested by TPBs. To identify salivary gland genes, mRNA was extracted from salivary glands and cDNA library clones were sequenced. A de novo-assembling of 7,000 Sanger sequences revealed 666 high-quality unique cDNAs with an average size of 624 bp, in which the identities of 347 cDNAs were determined using Blast2GO. Kyoto Encyclopedia of Genes and Genomes analysis indicated that these genes participate in eighteen metabolic pathways. Identifications of large number of enzyme genes in TPB salivary glands evidenced functions for extra-oral digestion and feeding damage mechanism, including 45 polygalacturonase, two α- amylase, one glucosidase, one glycan enzyme, one aminopeptidase, four lipase, and many serine protease cDNAs. The presence of multiple transcripts, multigene members, and high abundance of cell wall degradation enzymes (polygalacturonases) indicated that the enzyme-rich saliva may cause damage to plants by breaking down plant cell walls to make nutrients available for feeding. We also identified genes potentially involved in insect adaptation and detoxifying xenobiotics that may allow insects to overcome plant defense responses, including four glutathione S-transferases, three esterases, one cytochrome P450, and several serine proteases. The gene profiles of TPB salivary glands revealed in this study provides a foundation for further understanding and potential development of novel enzymatic inhibitors, or other RNAi approaches that may interrupt or minimize TPB feeding damage.

Differential expression of candidate salivary effector proteins in field collections of Hessian fly, Mayetiola destructor

Evidence is emerging that some proteins secreted by gall-forming parasites of plants act as effectors responsible for systemic changes in the host plant, such as galling and nutrient tissue formation. A large number of secreted salivary gland proteins (SSGPs) that are the putative effectors responsible for the physiological changes elicited in susceptible seedling wheat by Hessian fly, Mayetiola destructor (Say), larvae have been documented. However, how the genes encoding these candidate effectors might respond under field conditions is unknown. The goal of this study was to use microarray analysis to investigate variation in SSGP transcript abundance amongst field collections from different geographical regions (southeastern USA, central USA, and the Middle East). Results revealed significant variation in SSGP transcript abundance amongst the field collections studied. The field collections separated into three distinct groups that corresponded to the wheat classes grown in the different geographical regions as well as to recently described Hessian fly populations. These data support previous reports correlating Hessian fly population structure with micropopulation differences owing to agro-ecosystem parameters such as cultivation of regionally adapted wheat varieties, deployment of resistance genes and variation in climatic conditions.

Transcriptome analysis of the salivary glands of Nephotettix cincticeps (Uhler)

The green rice leafhopper (GRH), Nephotettix cincticeps, is one of the most important pests of rice in temperate Asian countries. GRH, a vascular feeder, secretes watery and gelling saliva in the process of feeding on phloem and xylem sap. It is known that GRH saliva contains several bioactive proteins, including enzymes such as laccase and beta-glucosidase. In this study, we performed transcriptome analysis of salivary glands of GRH using Illumina paired-end sequencing. Of 51,788 assembled contigs, 16,017 (30.9%) showed significant similarity to known proteins in the NCBI nr database, while 34,978 (67.5%) could not be annotated by similarity search, Pfam, or gene ontology (GO). Contigs (905) with predicted signal peptides and no putative transmembrane domains are suggested to represent secreted protein coding genes. Among the 76 most highly expressed putative secretory protein contigs, 68 transcripts were found to be salivary gland-specific or at least -dominant, but not expressed in stomach or Malpighian tubules. However, 45 of the 68 transcripts were unknown proteins. These findings suggest that most of the GRH transcripts encoding secreted proteins expressed in salivary glands are species and/or tissue specific. Our results provide a fundamental list of genes involved in GRH-Poaceae host plant interactions including successful feeding and plant pathogen transmission.

Comparative transcriptome analysis of salivary glands of two populations of rice brown planthopper, Nilaparvata lugens, that differ in virulence

Background

The brown planthopper (BPH), Nilaparvata lugens (Stål), a destructive rice pest in Asia, can quickly overcome rice resistance by evolving new virulent populations. Herbivore saliva plays an important role in plant–herbivore interactions, including in plant defense and herbivore virulence. However, thus far little is known about BPH saliva at the molecular level, especially its role in virulence and BPH–rice interaction.

Methodology/Principal Findings

Using cDNA amplification in combination with Illumina short-read sequencing technology, we sequenced the salivary-gland transcriptomes of two BPH populations with different virulence; the populations were derived from rice variety TN1 (TN1 population) and Mudgo (M population). In total, 37,666 and 38,451 unigenes were generated from the salivary glands of these populations, respectively. When combined, a total of 43,312 unigenes were obtained, about 18 times more than the number of expressed sequence tags previously identified from these glands. Gene ontology annotations and KEGG orthology classifications indicated that genes related to metabolism, binding and transport were significantly active in the salivary glands. A total of 352 genes were predicted to encode secretory proteins, and some might play important roles in BPH feeding and BPH–rice interactions. Comparative analysis of the transcriptomes of the two populations revealed that the genes related to ‘metabolism,’ ‘digestion and absorption,’ and ‘salivary secretion’ might be associated with virulence. Moreover, 67 genes encoding putative secreted proteins were differentially expressed between the two populations, suggesting these genes may contribute to the change in virulence.

Conclusions/Significance

This study was the first to compare the salivary-gland transcriptomes of two BPH populations having different virulence traits and to find genes that may be related to this difference. Our data provide a rich molecular resource for future functional studies on salivary glands and will be useful for elucidating the molecular mechanisms underlying BPH feeding and virulence differences.

Transcriptome analysis of the salivary glands of potato leafhopper, Empoasca fabae

The potato leafhopper, Empoasca fabae, is a pest of economic crops in the United States and Canada, where it causes damage known as hopperburn. Saliva, along with mechanical injury, leads to decreases in gas exchange rates, stunting and chlorosis. Although E. fabae saliva is known to induce plant responses, little knowledge exists of saliva composition at the molecular level. We subjected the salivary glands of E. fabae to Roche 454-pyrosequencing which resulted significant number (30,893) of expressed sequence tags including 2805 contigs and 28,088 singletons. A high number of sequences (78%) showed similarity to other insect species in GenBank, including Triboliumcastaneum, Drosophilamelanogaster and Acrythosiphonpisum. KEGG analysis predicted the presence of pathways for purine and thiamine metabolic, biosynthesis of secondary metabolites, drug metabolism, and lysine degradation. Pfam analysis showed a high number of cellulase and carboxylesterase protein domains. Expression analysis of candidate genes (alpha amylase, lipase, pectin lyase, etc.) among different tissues revealed tissue-specific expression of digestive enzymes in E. fabae. This is the first study to characterize the sialotranscriptome of E. fabae and the first for any species in the family of Cicadellidae. Due to the status of these insects as economic pests, knowledge of which genes are active in the salivary glands is important for understanding their impact on host plants.

Arabidopsis thaliana-Aphid Interaction

Aphids are important pests of plants that use their stylets to tap into the sieve elements to consume phloem sap. Besides the removal of photosynthates, aphid infestation also alters source-sink patterns. Most aphids also vector viral diseases. In this chapter, we will summarize on recent significant findings in plant-aphid interaction, and how studies involving Arabidopsis thaliana and Myzus persicae (Sülzer), more commonly known as the green peach aphid (GPA), are beginning to provide important insights into the molecular basis of plant defense and susceptibility to aphids. The recent demonstration that expression of dsRNA in Arabidopsis can be used to silence expression of genes in GPA has further expanded the utility of Arabidopsis for evaluating the contribution of the aphid genome-encoded proteins to this interaction.

Gall midges (Hessian flies) as plant pathogens

Gall midges constitute an important group of plant-parasitic insects. The Hessian fly (HF; Mayetiola destructor), the most investigated gall midge, was the first insect hypothesized to have a gene-for-gene interaction with its host plant, wheat (Triticum spp.). Recent investigations support that hypothesis. The minute larval mandibles appear to act in a manner that is analogous to nematode stylets and the haustoria of filamentous plant pathogens. Putative effector proteins are encoded by hundreds of genes and expressed in the HF larval salivary gland. Cultivar-specific resistance (R) genes mediate a highly localized plant reaction that prevents the survival of avirulent HF larvae. Fine-scale mapping of HF avirulence (Avr) genes provides further evidence of effector-triggered immunity (ETI) against HF in wheat. Taken together, these discoveries suggest that the HF, and other gall midges, may be considered biotrophic, or hemibiotrophic, plant pathogens, and they demonstrate the potential that the wheat-HF interaction has in the study of insect-induced plant gall formation.

Effect of fasting on digestive gland lipase transcripts expression in Penaeus vannamei

Digestive and intracellular lipases were studied in the digestive gland of whiteleg shrimp Penaeus vannamei. A partial sequence of the intracellular lipase was obtained from the digestive gland cDNA. The digestive and intracellular lipase mRNAs were detected differentially in different body parts of shrimp; digestive lipase mRNA is exclusively found in the digestive gland, suggesting a function as a digestive enzyme. Intracellular lipase mRNA was found in pleopods, digestive tube, uropods, hemocytes, muscle and gonad and its function was related to mobilization of energy reserves. The lipase transcripts in the digestive gland of shrimp, showed a dynamic expression at 120 h of fasting causing significant changes of digestive and intracellular mRNA, intracellular lipase mRNA were 3.33-fold higher than digestive lipase mRNA after fasting period, suggesting an alternate expression to maintain the lipid homeostasis under stress conditions.

Antibiosis against the green peach aphid requires the Arabidopsis thaliana MYZUS PERSICAE-INDUCED LIPASE1 gene

The green peach aphid (GPA) (Myzus persicae Sülzer) is an important sap-sucking pest of a large variety of plants, including Arabidopsis thaliana. Arabidopsis utilizes a combination of defenses that deter insects from settling on the plant, limit insect feeding and curtail insect reproduction. We demonstrate that the previously uncharacterized Arabidopsis MPL1 (MYZUS PERSICAE-INDUCED LIPASE1) gene has an important role in defense against the GPA. MPL1 expression was rapidly induced to high level in GPA-infested plants. Furthermore, the GPA population was larger on the mpl1 mutant than the wild-type (WT) plant. In contrast, constitutive over-expression of MPL1 from the Cauliflower mosaic virus 35S gene promoter curtailed the size of the GPA population. Insect settling and feeding behavior were unaffected on the mpl1 mutant. However, compared with the phloem-sap enriched petiole exudate from the WT plant, mpl1 petiole exudate was deficient in an activity that restricts insect reproduction on a synthetic diet. Furthermore, MPL1 was required for the heightened accumulation of an antibiotic activity in petiole exudate of the Arabidopsis ssi2 mutant, which exhibits enhanced resistance to GPA. These results indicate that MPL1 has an essential function in antibiosis against GPA. The MPL1 protein exhibits homology to lipases and recombinant MPL1 has lipase activity, thus suggesting that a MPL1-dependent lipid, or a product thereof, has an important role in antibiosis against GPA.

Robotic mechanical wounding (MecWorm) versus herbivore-induced responses: early signaling and volatile emission in Lima bean (Phaseolus lunatus L.)

Insect herbivory on plants is a complex incident consisting of at least two different aspects, mechanical damage and chemical factors. Only the combination of both is able to induce the respective plant defenses. Thus, diverse plant species emit volatile organic compounds (VOCs) in response to herbivory (HW), whereas mechanical damage inflicted as single wounding event (MD) does not induce increased VOC emissions. In contrast, a robotic worm (MecWorm, MW) allowed demonstrating that continuous mechanical damage is sufficient to induce volatile emission in Lima bean. However, the induced VOC blends remain characteristic for the respective stimulus. In order to identify putative differences in plant signaling leading to defenses, we compared time courses of early signals induced by wounding in Lima bean. Neither MD nor MW alone was able to induce plasma membrane (V (m)) depolarization, as observed after Spodoptera littoralis HW, but V (m) depolarization occurred in both treatments when used in combination with herbivore-derived oral secretions. A significant increase in cytosolic Ca(2+) concentrations was observed only after HW, whereas MD and MW did not affect this second messenger. H(2)O(2) was generated within 2-3 h after leaf damage by HW and MW, whereas MD induced only half of the H(2)O(2) levels compared to the other treatments. Both HW and MW induced a marked accumulation of NO, but with distinct temporal patterns. NO production after MD followed the same trend but reached significantly lower values. The results indicate that chemical signals from the herbivores are responsible for the induction of the earliest signaling events. These changes appear to be characteristic for the reaction to herbivory.

Changes in properties of wheat leaf cuticle during interactions with Hessian fly

Infestation of wheat by Hessian fly larvae causes a variety of physical and biochemical modifications of the host plant. Changes occur in cuticle permeability, lipid composition and gene transcript abundance, and these responses differ substantially between resistant and susceptible wheat lines. Staining assays revealed that susceptible plants exhibited a generalized increase in leaf sheath epidermal permeability during infestation; whereas, epidermal permeability was only minimally affected in resistant plants. Furthermore, temporal profiling using gas chromatographic methods revealed that changes in cuticle lipid (wax and cutin) composition correlated well with differing levels of epidermal permeability in susceptible and resistant plants. Temporal analysis of cuticle-associated gene mRNA levels, by quantitative real-time PCR, indicated a relationship between transcript abundance and changes in cuticle lipid profiles of resistant and susceptible plants. Results suggest that conserving cuticle integrity via induction of specific wax constituents and maintenance of cutin amounts, determined by the accumulation of cuticle-associated transcripts, could be important components of wheat resistance to Hessian fly larvae.