Transcriptome And Expression Profiling Studies On The Brown Planthopper Nilaparvata Lugens (St(?)l) In Response To Water Stress Rice

As an r-strategy and monophagous insect species on rice and wild rice(Oryza sativa and Oryza rufipogon), the brown planthopper, Nilaparvata lugens(St l), is one of the most destructive migratory pest of rice crops in the temperate andtropical regions of Asia and Australia, whichcauses serious yield losses and poses aconstant threat to rice supplies. Since the mid-1960s, the brown planthopperpopulation has increased due to changes of rice cultivation system brought byprecocious dwarf varieties in the south, as well as a large area of the northernexpansion of rice, a lot of irrational use of chemical pesticides and other factors. Andthese reasons create a very favorable ecological condition for brown planthoppers’seasonal north-south migration back and forth. Global climate change leads to spatialand temporal changes of surface precipitation. Extreme weather like droughts andfloods occured frequently and could have an impact on the brown planthopper.Studies on the impact of water stress to brown planthoppers are rare. How brownplanthoppers adapt to water stress is also rarely reported. In this study,5-leaf stage ofrice (TN1) were treated using polyethylene glycol6000(0and15%concentration),and then brown planthopper female adult feed these rices. We use transcriptomesequencing method to study the change of gene under water stress. The sequencingdata were verified by quantitative real-time PCR. The results are as follows:1. Differentially expressed genes of transcriptome sequencingWhen FDR and p-value was less than or equal to0.05as the threshold, brownplanthoppers in the treatment group had23significant differential genes comparedwith the control group, which the number of up-regulated genes was18and thenumber of down-regulated genes was5;1331significant differential transcripts,which the number of up-regulated transcripts was712and the number ofdown-regulated transcripts was619. When only p-value was less than or equal to0.05as the threshold, brown planthoppers in the treatment group had197significantdifferential genes, which the number of up-regulated genes was138and the numberof down-regulated genes was59;2850significant differential transcripts, which the number of up-regulated transcripts was1555and the number of down-regulatedtranscripts was1295.2. GO significant enrichment analysis results of differentially expressed genesThe upregulated number of GO terms in treatment group were38, thedown-regulated number of GO terms in treatment group were42. Metabolicprocesses, single-organism process, cell, catalytic activity and binding increasedsubstantially; immune system process, extracellular region, synapse, organelle part,structural molecule activity and molecular transducer activity decreased significantly.3. Pathway significant enrichment analysis of differentially expressed genesThere were179significantly enriched metabolic pathways in the treatmentgroup, related to622significant differential transcripts. Metabolic pathwayscontaining differentially expressed genes in top21: Spliceosome, Cell cycle, mRNAsurveillance pathway, Dorso-ventral axis formation, Phosphatidylinositol signalingsystem, RNAdegradation, Lysosome, Axon guidance, Inositol phosphate metabolism,RNA transport, Long-term potentiation, Aminoacyl-tRNA biosynthesis, Oxidativephosphorylation, Endocytosis, Oocyte meiosis, Peroxisome, Protein processing inendoplasmic reticulum, Ribosome biogenesis in eukaryotes, Calcium signalingpathway, Amino sugar and nucleotide sugar metabolism and Lysine degradation.Among179, there were39pathways participating in carbohydrates, lipids, proteins,feeding and water metabolism.4. Results of real-time quantitative PCR validationWe selected20significant differentially expressed genes randomly to verify thesequencing results. The result showed that80%of the gene expression tendency wasthe same between transcriptome sequencing results and qPCR results. In addition,the t test results confirmed the sequencing results. We verified the samples of24h,48h and72h by real-time quantitative PCR. The result of sample of72h had a largedifference with samples of24h and48h which was based on the t test results. Butthere was no significant difference between24h and48h.In summary, we analyzed the transcriptome sequencing result and got23differentially expressed genes and1331differentially expressed isogenes respondedto water stress by15%PEG,45enriched GO terms and179enriched pathways. Andwe extremely confirmed the sequencing results by real-time quantitative validation. At the same time, real-time quantitative test showed the time effectiveness ofsignificant expression genes was about2d. The study provided a theoretical basis forrevealing molecular mechanism of brown planthopper response to water stress.