Chilo Suppressalis Research Articles

Monitoring and Mechanisms of Chlorantraniliprole Resistance in Chilo suppressalis (Lepidoptera: Crambidae) in China.

Chlorantraniliprole, an anthranilic diamide insecticide, is widely used for controlling lepidopteran pests, because of its high insecticidal activity. However, overuse of chlorantraniliprole has led to the selection of resistance in many insect pests, including Chilo suppressalis (Lepidoptera:Crambidae), one of the most damaging rice pests in China. In this study, resistance levels to chlorantraniliprole for C. suppressalis was surveyed from eight populations of three provinces in China. The levels of resistance were ranged from 34.4-fold to 284.0-fold compared with a susceptible population. Then, a 15402 bp fragment of the full-length cDNA of ryanodine receptor gene (CsRyR) from the XS strain, the highest resistant population, and a 1992 bp fragment of CsRyR cDNA encoding the carboxyl-terminal of CsRyR gene from the other seven populations were sequenced. A common previously identified mutation that was associated with chlorantraniliprole resistance against C. suppressalis, G4910E, was not detected in any of the eight populations in this study. However, another mutation I4758M was found in all seven resistant populations. Furthermore, the relative mRNA expression levels of CsRyR gene in the seven resistant populations were all reduced compared with susceptible strain. Our study provides new insights into the basis of monitoring the development of resistance and the mechanism of resistance to chlorantraniliprole in C. suppressalis.

Molecular characterization of glutamate-gated chloride channel and its possible roles in development and abamectin susceptibility in the rice stem borer, Chilo suppressalis

Glutamate-gated chloride channels (GluCls) mediate fast inhibitory neurotransmission in invertebrate nervous systems, and are of considerable interest in insecticide discovery. The full length cDNA encoding CsGluCl was cloned from the rice stem borer Chilo suppressalis (Walker). Multiple cDNA sequence alignment revealed three variants of CsGluCl generated by alternative splicing of exon 3 and exon 9. While all the transcripts were predominantly expressed in both nerve cord and brain, the expression patterns of these three variants differed among other tissues and developmental stages. Specifically, the expression level of CsGluCl C in cuticle was similar to that in nerve cord and brain, and was the predominant variant in late pupae and early adult stages. Both injection and oral delivery of dsGluCl significantly reduced the mRNA level of CsGluCl. Increased susceptibility to abamectin and reduced larvae growth and pupation rate were observed in dsGluCl-treated larvae. Thus, our results provide the evidence that in addition to act as the target of abamectin, GluCls also play important physiological roles in the development of insects.

Identification of the ionotropic GABA receptor-like subunits from the striped stem borer, Chilo suppressalis Walker (Lepidoptera: Pyralidae)

Ionotropic γ-aminobutyric acid (GABA) receptors (GABARs) mediate rapid inhibitory neurotransmission in both vertebrates and invertebrates, and are important molecular targets of insecticides. However, components of insect GABARs remain elusive. In addition to CsRDL1 and CsRDL2, the complementary DNAs (cDNAs) of another two GABA receptor-like subunits, CsLCCH3 and Cs8916, were identified from the rice striped stem borer, Chilo suppressalis Walker in the present study. Both CsLCCH3 and Cs8916 subunits shared common structural features, such as a highly-conserved Cys-loop structure, six distinct regions involved in ligand binding (loops A-F), and four transmembrane domains (TM 1-4). Transcript analysis demonstrated that the relative mRNA expression levels of both CsLCCH3 and Cs8916 subunits were the highest in the ventral nerve cord. Regarding developmental stage, transcript levels of both subunits were highest in eggs. Injections of double-stranded RNAs (dsRNAs), including dsRDL1, dsRDL2, dsLCCH3, or ds8916, significantly reduced mRNA abundance after 24 and 48 h. However, no observable effects on the development of C. suppressalis were observed. Injection of dsRDL1 or dsRDL2 did significantly reduce the mortality of C. suppressalis treated with fluralaner. Our results indicated that CsRDLs mediated the susceptibility of C. suppressalis to fluralaner, whereas CsLCCH3 and CsL8916 did not. The current investigation enhances our knowledge of Lepidopteran GABARs and offers a molecular basis for the development of novel insecticides to control C. suppressalis.

Quantification of Serotonin in Rice and Insect Pest and its Functional Analysis in Insects Using Artificial Diet Feeding.

Rice is one of the world's most important crops, but its production suffers from insect pests. Rice brown planthopper (BPH; Nilaparvata lugens Stål) and striped stem borer (SSB, Chilo suppressalis Walker) are the two most serious pests in rice production. We reported that serotonin is an essential mediator in the interaction between rice and insect. Here, we established a method for extraction and determination of serotonin in rice and BPH.

Minor Components Play an Important Role in Interspecific Recognition of Insects: A Basis to Pheromone Based Electronic Monitoring Tools for Rice Pests.

Several lepidopteran species share the same pheromone blend consisting of (Z)-11-hexadecenal (Z11-16:Ald) and (Z)-9-hexadecenal (Z9-16:Ald) at different ratios and active doses. In rice pest Chilo suppressalis, (Z)-11-hexadecenol, (Z11-16:OH) and octadecanal (18:Ald) were identified as minor components in the pheromone gland of female moths, and these components were previously not considered as part of the sex pheromone of C. suppressalis. Z11-16:Ald, Z9-16:Ald and (Z)-13-octadecenal (Z13-18:Ald) frequently trapped other lepidopteran species, such as rice pests Scirpophaga incertulas and Mythimna separate, corn and vegetable pests Helicoverpa armigera in the field, suggesting a lack of specificity in the pheromone blend. Our data showed that the minor component Z11-16:OH did not have a synergistic effect on the attractiveness of the blend to C. suppressalis; however, pheromone mixtures containing Z11-16:OH failed in trapping male H. armigera moths. We confirmed the identity and specificity of the C. suppressalis sex pheromone and demonstrated that Z11-16:OH plays a key role in the reproductive isolation of C. suppressalis, M. separata, and H. armigera moths, and a similar role of Z9-18:Ald in that of S. incertulas and C. suppressalis. This phenomenon could be more widely applicable to interspecific interactions in the pheromone communication between insects, which is crucial to developing the electronic automatic counting device for automatically monitoring the pest population by pheromone trapping based on its species specificity.

Comparative Transcriptome Analysis Between Resistant and Susceptible Rice Cultivars Responding to Striped Stem Borer (SSB), Chilo suppressalis (Walker) Infestation.

The striped stem borer, Chilo suppressalis (Walker), is a notorious pest of rice that causes large losses in China. Breeding and screening of resistance rice cultivars are effective strategies for C. suppressalis management. In this study, insect-resistant traits of 47 rice cultivars were investigated by C. suppressalis artificial infestation (AI) both in field and greenhouse experiments, using the susceptible (S) cultivar 1665 as a control. Results suggest that two rice cultivars, namely 1688 and 1654, are resistant (R) and moderately resistant (MR) to C. suppressalis, respectively. Then, a comparative transcriptome (RNA-Seq) was de novo assembled and differentially expressed genes (DEGs) with altered expression levels were investigated among cultivars 1688, 1654, and 1665, with or without C. suppressalis infestation for 24 h. A total of 2569 and 1861 genes were up-regulated, and 3852 and 1861 genes were down-regulated in cultivars 1688 and 1654, respectively after artificial infestation with C. suppressalis compared to the non-infested control (CK). For the susceptible cultivar 1665, a total of 882 genes were up-regulated and 3863 genes were down-regulated after artificial infestation with C. suppressalis compared to the CK. Twenty four DEGs belong to proteinase inhibitor, lectin and chitinase gene families; plant hormone signal transduction and plant-pathogen interaction pathways were selected as candidate genes to test their possible role in C. suppressalis resistance. RT-qPCR results revealed that 13 genes were significantly up-regulated and 8 were significantly down-regulated in the resistant cultivar 1688 with C. suppressalis artificial infestation (1688AI) compared to the CK. Three genes, LTPL164, LTPL151, and LOC Os11g32100, showed more than a 10-fold higher expression in 1688AI than in 1688CK, suggesting their potential role in insect resistance. Overall, our results provide an important foundation for further understanding the insect resistance mechanisms of selected resistant varieties that will help us to breed C. suppressalis resistant rice varieties.

Knockdown of the GABA receptor RDL genes decreases abamectin susceptibility in the rice stem borer, Chilo suppressalis

The γ-aminobutyric acid (GABA) receptor is a primary neurotransmitter receptor in both vertebrate and invertebrate nervous systems. Multiple RDL subunits have been found in insects including the rice stem borer, Chilo suppressalis, however, comparative characterization of duplicated RDL genes in insects is still limited. In this study, comparison of the genomic sequences and the cDNA sequences revealed that both CsRDL1 and CsRDL2 consisted of 10 exons and 9 introns, and their exon-intron boundaries occur in the same position with respect to the coding sequences. Expression profiling showed that both CsRDL1 and CsRDL2 were predominantly expressed in nervous system, and had low expression levels in the gut and integument. The transcript level of CsRDL2 dramatically increased from the prepupae to late pupae and were much higher than that of CsRDL1 in adult stages. Notably, dietary ingestion of dsRDL1 and dsRDL2 significantly decreased the larval susceptibility to abamectin. These results suggest that CsRDL1 and CsRDL2 might play both physiological roles in development and toxicological roles in action of abamectin in C. suppressalis.

Effect of rearing conditions on the correlation between larval development time and pupal weight of the rice stem borer, Chilo suppressalis.

A strong positive correlation between development time and body size is commonly assumed. However, the evidence is increasing that the correlation between the two traits can be positive, zero or negative, depending on whether the two traits are under antagonistic or synergistic selection. In the present study, we examined the relation between larval development time and pupal weight of the rice stem borer Chilo suppressalis under laboratory and field conditions. For individuals reared at constant temperatures (22, 25, 28 and 31°C), a longer larval period tended to result in larger pupae, showing a positive correlation between larval development time and pupal weight; whereas for those reared under field conditions, a longer larval period tended to result in smaller pupae at 23.5 and 29.8°C, showing a negative correlation between the two traits. There was no correlation between the two traits at the mean daily temperature of 31°C. At constant temperatures, larval development time shortened significantly as rearing temperature increased, whereas pupae tended to become larger at higher temperatures, although no significant difference was detected among temperatures for pupal weight. Under field conditions, larval development time decreased significantly as the mean daily temperature increased, whereas pupal weight of females increased significantly with the increase in the mean daily temperature, which is an example of the reverse temperature–size rule. Feeding method significantly affected larval development time and pupal weight. For individuals fed on live rice plants, larval development time shortened significantly and pupal weight increased significantly compared with those reared on fresh rice stems.

Characterization of transgenic rice expressing fusion protein Cry1Ab/Vip3A for insect resistance

Management of resistance development of insect pests is of great importance for continued utilization of Bt crop. The high-dose/refuge and pyramid (gene stacking) strategy are commonly employed to delay the evolution of insect resistance. Due to the anticipated difficulty for deployment of mandatory refuge for transgenic crops in China, where the size of farmer is quite small, stacking of genes with different modes of action is a more feasible strategy. Here we report the development of transgenic rice expressing a fusion protein of Cry1Ab and Vip3A toxin. Analysis of trypsin proteolysis suggested that the fusion protein is equivalent to the combination of Cry1Ab and Vip3A protein. The transgenic plants expressing the fusion protein were found to be highly resistant to two major rice pests, Asiatic rice borer Chilo suppressalis (Lepidoptera: Crambidae) and rice leaf folder Cnaphalocrocis medinalis (Lepidoptera: Crambidae), while their agronomic performances showed no significant difference compared to the non-transgenic recipient rice. Therefore, the transgenic rice may be utilized for rice pest control in China.

Simultaneous effects of thermal stress and fungal infection on lipid peroxidation and antioxidant system of rice-striped stem borer, Chilo suppressalis Walker (Lepidoptera: Crambidae)

ABSTRACTThe effects of thermal stress, time of exposure, and infection by Beauveria bassiana were determined on the lipid peroxidation and antioxidant system of Chilo suppressalis Walker. The larvae were exposed to 24°C and 34°C for, respectively, 24 h and 72 h. Then, these two groups of larvae were divided into three subgroups: intact larvae, larvae injected with 80 μg/ml of Tween-80 (0.02%), and larvae injected with 104 spores/ml of Beauveria bassiana suspended in 80 μg/ml of Tween-80 (0.02%). The highest activities of superoxide dismutase and peroxidase were found in larvae injected with B. bassiana at both thermal regimes, while the activity of catalase was lowest in these treatments. Highest activities of glutathione S-transferase, glucose-6-phosphate dehydrogenase, and ascorbate peroxidase were observed in the larvae injected with B. bassiana at both thermal regimes. Finally, thermal stress and fungal injection led to the highest amounts of Malondialdehyde and the ratio of oxidized and reduced thiols at both thermal regimes. In our study, the simultaneous exposure of C. suppressalis to thermal stress and B. bassiana infection significantly increased the concentration of oxidative agents in the body of treated larvae, indicating that the antioxidant system may have a role in larval defense.Abbreviations: SOD: Superoxide dismutase; POX: Peroxidase; CAT: Catalase; APOX: Ascorbate peroxidase; GPDH: Glucose-6-Phosphate dehydrogenase; GSTs: Glutathione S-transferases; MDA: Malondialdehyde; RSSR/RSH: Oxidized and reduced thiols.

Constitutive overexpression of cytochrome P450 monooxygenase genes contributes to chlorantraniliprole resistance in Chilo suppressalis (Walker).

The rice striped stem borer (SSB), Chilo suppressalis (Walker), which is one of the most economically important phytophagous pests, has developed resistance to multiple insecticides. The resistance of SSB against chlorantraniliprole has been investigated in detail. However, the mechanism of its metabolic resistance has rarely been studied. A field population from Wuhu City, China was used to establish chlorantraniliprole resistant and susceptible strains (WHR and WHS) by laboratory continuous selection. Enzyme activities data suggested the potential involvement of cytochrome P450 monooxygenase in WHR. CYP6CV5, CYP9A68, CYP321F3, and CYP324A12 were significantly overexpressed in WHR (from 4.48 to 44.88-fold). These four P450 genes were expressed in the late developmental stages of WHR; however, they were almost absent during the egg stage. In addition, their expressions were much more sensitive to chlorantraniliprole induction in WHR than in WHS. Injection of individual and mixture dsRNAs reduced the expression of the four target genes (55.2-73.2% and 43.2-50.2%, respectively) and caused significant larvae mortality (55.1-65.1% and 88.2%, respectively). Multiple overexpressed P450 genes were potentially associated with chlorantraniliprole resistance, as confirmed by the RNA interference (RNAi) assay. Our findings suggested that metabolic resistance to chlorantraniliprole might be mediated by P450s. © 2018 Society of Chemical Industry.

Functional analysis of eight chitinase genes in rice stem borer and their potential application in pest control

Insect chitinases participate in numerous physiological processes such as nutrition, parasitism, morphogenesis and immunity. These properties make chitinases good targets for pest control. Rice striped stem borer (SSB), Chilo suppressalis Walker, is one of the most destructive pests of rice causing huge yield losses. In our previous work, we reported the identification of 12 SSB chitinase (CsCht) genes, and studied the functions of CsCht1 to 4. Here, we have extended our study to investigate the expression patterns and functions of CsCht5 to 12. All eight chitinase genes displayed distinct temporospatial expression profiles. We looked at the effect of knocking down each gene at the developmental stage where highest expression was observed. Knocking down CsCht5, CsCht6 and CsCht8 resulted in high mortality and delayed development. Although silencing CsCht7, CsCht9, CsCht10, CsCht11 and CsCht12 had no apparent effect on development, knocking down CsCht10 in SSB individuals that were simultaneously treated with Beauveria bassiana (Bb84) led to higher mortality rates and quicker death, suggesting CsCht10 has an essential role in protecting SSB from exogenous microorganisms. In summary, we elucidated the functions of eight SSB chitinase genes and found that CsCht10 could be a good candidate for pest control.

Expression Profile and Functional Characterization Suggesting the Involvement of Three Chemosensory Proteins in Perception of Host Plant Volatiles in Chilo suppressalis (Lepidoptera: Pyralidae).

The high sensitivity of the olfactory system is essential for feeding and oviposition in moth insects, and some chemosensory proteins (CSPs) are thought to play roles in this system by binding and carrying hydrophobic odorants across the aqueous sensillar lymph. In this study, to identify the olfactory CSPs from a repertoire of 21 CSP members in the notorious rice pest Chilo suppressalis (Walker) (Lepidoptera: Pyralidae), tissue expression patterns were firstly examined by quantitative real-time polymerase chain reaction (qPCR). It showed that CSP2 was antennae specific and seven more CSPs (CSP1, 3, 4, 6, 15, 16, and 17) were antennae biased in expression, suggesting their olfactory roles; while other CSPs were multiple-tissue expressed and non-antennae biased, suggesting other functions for these genes. To further determine the ligand binding specificity, three putative olfactory genes (CSP1–3) were expressed in Escherichia coli cells, and binding affinity of these three recombinant CSP proteins were measured for 35 plant volatiles by the ligand binding assays. CSP1 and CSP2 exhibited high binding affinities (Ki ≤ 10.00 µM) for four (2-tridecanone, benzaldehyde, laurinaldehyde and 2-pentadecanone) and two (2-heptanol and (+)-cedrol) host plant volatiles, respectively; the three CSPs also showed moderate binding affinity (Ki = 10.01–20.00 µM) for 16 plant volatiles. Our study suggests that the three CSPs play essential roles in the perception of host plant volatiles, providing bases for the elucidation of olfactory mechanisms in this important pyralid pest.

Divergence in larval diapause induction between the rice and water-oat populations of the striped stem borer, Chilo suppressalis (Walker) (Lepidoptera: Crambidae).

Differences in diapause traits can result in the seasonal reproductive isolation of host plant-associated insect populations and thereby facilitate the population divergence. The striped stem borer, Chilo suppressalis, has two host plant-associated populations: rice population and water-oat population. Several studies have found evidence that seasonal reproductive isolation between these populations is at least partially due to interpopulation differences in diapause. However, there still lack unambiguous evidence comparing characteristics of diapause induction for both populations. We compared the photoperiodic response and the age of peak photoperiod sensitivity of these populations and used RNA-Seq to compare the molecular response of diapause induction between populations. The photoperiodic response of the two populations differed at 25°C; the critical night length of larvae from the rice population was 11h and 20min, whereas no obvious critical night length was in those from the water-oat population. In rice population, larvae were most sensitive to photoperiod at 9-12days of age, whereas in water-oat population, larvae were the most sensitive to photoperiod at 9-10days of age. The RNA-Seq results indicated that there were several differences in the molecular response of diapause induction and small overlap in differentially expressed genes (DEGs) between populations. Furthermore, GO analysis indicated that both rice and water-oat population's DEGs were significantly enriched in heme and iron binding. Besides, water-oat population's DEGs were significantly enriched in metabolizing nutrients but rice population's DEGs do not. Thus, our results described differences in diapause induction between rice and water-oat populations of C. suppressalis which could affect the timing of diapause and thereby contribute to the seasonal reproductive isolation of these host plant-associated populations. In conclusion, this work suggests that difference in diapause induction could promote the population divergence in insects associated with different host plants.

Transgenic microRNA-14 rice shows high resistance to rice stem borer.

SummaryRice stem borer (RSB, Chilo suppressalis) is an insect pest that causes huge economic losses every year. Control efforts rely heavily on chemical insecticides, which leads to serious problems such as insecticide resistance, environment pollution, and food safety issues. Therefore, developing alternative pest control methods is an important task. Here, we identified an insect‐specific microRNA, miR‐14, in RSB, which was predicted to target Spook (Spo) and Ecdysone receptor (EcR) in the ecdysone signalling network. In‐vitro dual luciferase assays using HEK293T cells confirmed the interactions of Csu‐miR‐14 with CsSpo and with CsEcR. Csu‐miR‐14 exhibited high levels of expression at the end of each larval instar stage, and its expression was negatively correlated with the expression of its two target genes. Overexpression of Csu‐miR‐14 at the third day of the fifth instar stage led to high mortality and developmental defects in RSB individuals. We produced 35 rice transformants to express miR‐14 and found that three lines had a single copy with highly abundant miR‐14 mature transcripts. Feeding bioassays using both T0 and T1 generations of transgenic miR‐14 rice indicated that at least one line (C#24) showed high resistance to RSB. These results indicated that the approach of miRNAs as targets has potential for improving pest control methods. Moreover, using insect‐specific miRNAs rather than protein‐encoding genes for pest control may prove benign to non‐insect species, and thus is worthy of further exploration.

Herbivore-induced rice resistance against rice blast mediated by salicylic acid.

In agro-ecosystems, plants are important mediators of interactions between their associated herbivorous insects and microbes, and any change in plants induced by one species may lead to cascading effects on interactions with other species. Often, such effects are regulated by phytohormones such as jasmonic acid (JA) and salicylic acid (SA). Here, we investigated the tripartite interactions among rice plants, three insect herbivores (Chilo suppressalis, Cnaphalocrocis medinalis or Nilaparvata lugens), and the causal agent of rice blast disease, the fungus Magnaporthe oryzae. We found that pre-infestation of rice by C. suppressalis or N. lugens but not by C. medinalis conferred resistance to M. oryzae. For C. suppressalis and N. lugens, insect infestation without fungal inoculation induced the accumulation of both JA and SA in rice leaves. In contrast, infestation by C. medinalis increased JA levels but reduced SA levels. The exogenous application of SA but not of JA conferred resistance against M. oryzae. These results suggest that pre-infestation by C. suppressalis or N. lugens conferred resistance against M. oryzae by increasing SA accumulation. These findings enhance our understanding of the interactions among rice plant, insects and pathogens, and provide valuable information for developing an ecologically sound strategy for controlling rice blast.

Bt rice plants may protect neighbouring non-Bt rice plants against the striped stem borer, Chilo suppressalis.

The area planted with insect-resistant genetically engineered crops expressing Bacillus thuringiensis (Bt) genes has greatly increased in many areas of the world. Given the nearby presence of non-Bt crops (including those planted as refuges) and non-crop habitats, pests targeted by the Bt trait have a choice between Bt and non-Bt crops or weeds, and their host preference may greatly affect insect management and management of pest resistance to Bt proteins. In this study, we examined the oviposition preference of the target pest of Bt rice, Chilo suppressalis, for Bt versus non-Bt rice plants as influenced by previous damage caused by C. suppressalis larvae. The results showed that C. suppressalis females had no oviposition preference for undamaged Bt or non-Bt plants but were repelled by conspecific-damaged plants whether Bt or non-Bt. Consequently, C. suppressalis egg masses were more numerous on Bt plants than on neighbouring non-Bt plants both in greenhouse and in field experiments due to the significantly greater caterpillar damage on non-Bt plants. We also found evidence of poorer performance of C. suppressalis larvae on conspecific-damaged rice plants when compared with undamaged plants. GC-MS analyses showed that larval damage induced the release of volatiles that repelled mated C. suppressalis females in wind tunnel experiments. These findings suggest that Bt rice could act as a dead-end trap crop for C. suppressalis and thereby protect adjacent non-Bt rice plants. The results also indicate that the oviposition behaviour of target pest females should be considered in the development of Bt resistance management strategies.

Distribution and degradation kinetics of cyhalodiamide in Chinese rice field environment

Abstract Cyhalodiamide is a novel agrochemical which is effective against Lepidoptera pests, including Cnaphalocrocis medinalis, Chilo suppressalis, Pieris rapae, Plutella xylostella, Helicoverpa armigera, etc. In the study, a fast and accurate analytical method was developed to detect cyhalodiamide in Chinese typical rice field environment by a modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged, Safe) method with UPLC-MS/MS (ultra-high performance chromatography-tandem mass spectrometry). The mean recoveries of cyhalodiamide varied from 73.5% to 107.5%, with the RSDs from 1.2% to 10.7%. The limits of determination (LODs) were 0.0005 mg·kg− 1, and the limits of quantitation (LOQs) were from 0.002 to 0.01 mg·kg− 1 in all five matrices. This method was used to determine cyhalodiamide residues for studies of the distribution and degradation kinetics in rice field environment. The field trials results showed that cyhalodiamide was easily degradable and the half-lives were 4.2–13.6 d in rice straw, 8.77 d in paddy soil and 5.37–8.45 d in paddy water, respectively. The final residues of cyhalodiamide in brown rice were below 0.35 mg·kg− 1. The used dosage of 33.75 g·hm− 2 with pre-harvest interval (PHI) of 21 d and the maximum residue limit (MRL) of cyhalodiamide in rice at 0.1 mg·kg− 1 were recommended, which would be safe to human health and environment. The developed analytical method will be useful to monitor cyhalodiamide residues and safety evaluation in rice environment.

Molecular Characterization of a Mitochondrial Manganese Superoxide Dismutase From Chilo suppressalis (Lepidoptera: Crambidae).

In insects, superoxide dismutases (SODs) play a critical role in the scavenging of harmful reactive oxygen species (ROS) and protecting against oxidative stress induced by various environmental stresses. The Asiatic rice borer, Chilo suppressalis (Walker) (Lepidoptera: Crambidae), is an economically important insect pest of rice crops. In this study, a mitochondrial manganese SOD (Cs-mMnSOD) gene was characterized in C. suppressalis. The deduced Cs-mMnSOD protein has typical highly conserved features of mitochondrial manganese SODs, including four manganese binding residues, the signature DVWEHAYY peptide, and a mitochondrial-targeting sequence at the N-terminus. Transcription of Cs-mMnSOD was detectable at all developmental stages, but highest in pupae. Furthermore, the mRNA level of Cs-mMnSOD was strongly upregulated (more than twofold increase) following exposure to low and high temperatures (4, 30 and 35°C), insecticides (chlorpyrifos and chlorantraniliprole), and chemical reagents (cumene hydroperoxide, paraquat, H2O2 and CdCl2), but slightly elevated (less than twofold increase) in response to 8°C, abamectin and CuSO4. Additionally, the Cs-mMnSOD transcription results were consistent with the enzymatic activity data of the protein product. Purified recombinant Cs-mMnSOD protein expressed in Escherichia coli displayed SOD activity and thermostability. Furthermore, E. coli cells overexpressing Cs-mMnSOD exhibited long-term resistance to the oxidative inducers cumene hydroperoxide and paraquat. Our findings indicate that Cs-mMnSOD plays an important role in protecting C. suppressalis against oxidative damage.

OsLRR-RLK1, an early responsive leucine-rich repeat receptor-like kinase, initiates rice defense responses against a chewing herbivore.

Plants are constantly exposed to a variety of environmental stresses, including herbivory. How plants perceive herbivores on a molecular level is poorly understood. Leucine-rich repeat receptor-like kinases (LRR-RLKs), the largest subfamily of RLKs, are essential for plants to detect external stress signals, and may therefore also be involved in herbivore perception. Here, we employed RNA interference silencing, phytohormone profiling and complementation, as well as herbivore resistance assays, to investigate the requirement of an LRR-RLK for the initiation of rice (Oryza sativa) defenses against the chewing herbivore striped stem borer (SSB) Chilo suppressalis. We discovered a plasma membrane-localized LRR-RLK, OsLRR-RLK1, whose transcription is strongly up-regulated by SSB attack and treatment with oral secretions of Spodoptera frugiperda. OsLRR-RLK1 acts upstream of mitogen-activated protein kinase (MPK) cascades, and positively regulates defense-related MPKs and WRKY transcription factors. Moreover, OsLRR-RLK1 is a positive regulator of SSB-elicited, but not wound-elicited, levels of jasmonic acid and ethylene, trypsin protease inhibitor activity and plant resistance towards SSB. OsLRR-RLK1 therefore plays an important role in herbivory-induced defenses of rice. Given the well-documented role of LRR-RLKs in the perception of stress-related molecules, we speculate that OsLRR-RLK1 may be involved in the perception of herbivory-associated molecular patterns.