Project description:BACKGROUND:Chilo suppressalis is a widespread rice pest that poses a major threat to food security in China. This pest can develop resistance to Cry toxins from Bacillus thuringiensis (Bt), threatening the sustainable use of insect-resistant transgenic Bt rice. However, the molecular basis for the resistance mechanisms of C. suppressalis to Cry1C toxin remains unknown. This study aimed to identify genes associated with the mechanism of Cry1C resistance in C. suppressalis by comparing the midgut transcriptomic responses of resistant and susceptible C. suppressalis strains to Cry1C toxin and to provide information for insect resistance management. RESULTS:A C. suppressalis midgut transcriptome of 139,206 unigenes was de novo assembled from 373 million Illumina HiSeq and Roche 454 clean reads. Comparative analysis identified 5328 significantly differentially expressed unigenes (DEGs) between C. suppressalis Cry1C-resistant and -susceptible strains. DEGs encoding Bt Cry toxin receptors, aminopeptidase-P like protein, the ABC subfamily and alkaline phosphatase were downregulated, suggesting an association with C. suppressalis Cry1C resistance. Additionally, Cry1C resistance in C. suppressalis may be related to changes in the transcription levels of enzymes involved in hydrolysis, digestive, catalytic and detoxification processes. CONCLUSION:Our study identified genes potentially involved in Cry1C resistance in C. suppressalis by comparative transcriptome analysis. The assembled and annotated transcriptome data provide valuable genomic resources for further study of the molecular mechanisms of C. suppressalis resistance to Cry toxins.
Project description:The rice stem borer, Chilo suppressalis (Walker) (Lepidoptera: Pyralidae), is one of the most detrimental pests affecting rice crops. The use of Bacillus thuringiensis (Bt) toxins has been explored as a means to control this pest, but the potential for C. suppressalis to develop resistance to Bt toxins makes this approach problematic. Few C. suppressalis gene sequences are known, which makes in-depth study of gene function difficult. Herein, we sequenced the midgut transcriptome of the rice stem borer. In total, 37,040 contigs were obtained, with a mean size of 497 bp. As expected, the transcripts of C. suppressalis shared high similarity with arthropod genes. Gene ontology and KEGG analysis were used to classify the gene functions in C. suppressalis. Using the midgut transcriptome data, we conducted a proteome analysis to identify proteins expressed abundantly in the brush border membrane vesicles (BBMV). Of the 100 top abundant proteins that were excised and subjected to mass spectrometry analysis, 74 share high similarity with known proteins. Among these proteins, Western blot analysis showed that Aminopeptidase N and EH domain-containing protein have the binding activities with Bt-toxin Cry1Ac. These data provide invaluable information about the gene sequences of C. suppressalis and the proteins that bind with Cry1Ac.
Project description:The striped stem borer, Chilo suppressalis Walker (Lepidoptera: Crambidae), is one of the most serious rice pests. Besides attacking rice, it also feeds on an economically important vegetable crop, water-oat Zizania latifolia. The species feeding on water-oat has higher growth and survival rate than those on rice, suggesting their success in adaptation to the new host plant. However, little is known about the molecular mechanisms of host plant adaptation. Here we investigated the midgut transcriptome responses of C. suppressalis larvae reared on rice and water-oat. A total of 1,633 differentially expressed genes were identified, with a greater number up-regulated on the more delicious new host. The up-regulation of most digestive and detoxification-related genes may be the result of adaptation to the changes in nutritional requirements and toxic chemicals during host shift. In contrast, down-regulation of ribosomal genes may be related to their better development performance when feeding on the new host. In conclusion, our results suggest that transcriptional regulation of genes related to digestion, detoxification and ribosome may play an important role in adaptation of C. suppressalis to a new host plant.
Project description: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.
Project description:Diapause is a complex and dynamic process. Chilo suppressalis, an important rice pest in Asia enters facultative diapause as larvae. Our results demonstrated in Yangzhou, China, diapause was initiated between September 4 and 12, 2010. After diapause termination, C. suppressalis remained in quiescence in the field for as long as three months. The average time between collection of field larvae of C. suppressalis and their pupation decreased as the season progressed from fall to next spring. Unexpectedly, the pupated ratio of female to male in the initiation of diapause was 0.22. The abundance of hsp90, hsp70, hsp60 and CsAQP1 all peaked on January 8 or 15, 2011. Nitric oxide (NO) is a secondary messenger that is positively correlated with the diapause of C. suppressalis. Among several geographically separated populations of C. suppressalis, there are no significant differences in the mRNA levels of hsp70, hsp60 or CsAQP1.
Project description:Bacillus thuringiensis (Bt) Cry toxins play an important role in the management of insect pests. Resistance to Bt toxins has been reported in many pest insects but the mechanism responsible for this resistance in rice crop pests remains largely unknown. Cadherin is one of several Bt toxin receptors. At present, only one cadherin gene, CsCAD1, has been documented in the striped rice stem borer, Chilo suppressalis. We amplified a nearly full-length transcript of another C. suppressalis cadherin gene, CsCAD2, and found that it has a different expression pattern to CsCAD1. CsCAD1 was highly expressed in fifth and sixth instar larvae, especially in the midgut, while the expression levels of CsCA2 were equably in each developmental stage. Newly hatched larvae were fed on rice smeared with synthesized siRNA to knockdown either CsCAD1 or CsCAD2, and then were fed transgenic rice expressing either the Cry2A or Cry1C toxins. The siRNA-treatment groups had lower mortality and higher survival rates than the control group, suggesting that reduced expression of CsCAD1 or CsCAD2 increased resistance to Cry2A and Cry1C. We conclude that CsCAD1 and CsCAD2 interact with Bt toxins in C. suppressalis and that this interaction could be the mechanism underlying Bt resistance in this insect.
Project description:Neurotransmitter signaling systems play crucial roles in multiple physiological and behavioral processes in insects. Genome wide analyses of de novo transcriptome sequencing and gene specific expression profiling provide rich resources for studying neurotransmitter signaling pathways. The rice striped stem borer, Chilo suppressalis is a destructive rice pest in China and other Asian countries. The characterization of genes involved in neurotransmitter biosynthesis and transport could identify potential targets for disruption of the neurochemical communication and for crop protection.Here we report de novo sequencing of the C. suppressalis central nervous system transcriptome, identification and expression profiles of genes putatively involved in neurotransmitter biosynthesis, packaging, and recycling/degradation. A total of 54,411 unigenes were obtained from the transcriptome analysis. Among these unigenes, we have identified 32 unigenes (31 are full length genes), which encode 21 enzymes and 11 transporters putatively associated with biogenic aminergic signaling, acetylcholinergic signaling, glutamatergic signaling and GABAergic signaling. RT-PCR and qRT-PCR results indicated that 12 enzymes were highly expressed in the central nervous system and all the transporters were expressed at significantly high levels in the central nervous system. In addition, the transcript abundances of enzymes and transporters in the central nervous system were validated by qRT-PCR. The high expression levels of these genes suggest their important roles in the central nervous system.Our study identified genes potentially involved in neurotransmitter biosynthesis and transport in C. suppressalis and these genes could serve as targets to interfere with neurotransmitter production. This study presents an opportunity for the development of specific and environmentally safe insecticides for pest control.