Exploring The Molecular Mechanisms Underlying The Resistance Of Camellia Sinensis To Ectropis Oblique Provided By Transcriptomic Comparisons

Ectropis oblique is a specialist geometrid that feeds on tea plant(Camellia sinensis) and causes serious damage in the southern areas of China. Molecular breeding of tea plant for tea geometrid resistance draws various tea producing countries’ attention. The studies on the mechanisms of resistance to E. oblique by tea plants are the foundation of creating new insect-resistance materials. Tea plants have generated a series of mechanisms to resist two processes related to E. oblique feeding: mechanical damage and oral secretion stimuli. We employed RNA-sequencing(RNA-Seq) to compare three genome-wide expression profiles of a mechanically damaged plant, geometrid-damaged plant and undamaged control to elucidate the molecular mechanisms, and used real-time quantitative PCR(q RT-PCR) to verify the results by RNA-Seq. And on the basis of sequencing data we excavated for 9 NBS-LRR-like resistance sequences Cs NBSs, and detected Cs NBS1 and Cs NBS2 expression patterns in different resistance tea plants after E. oblique damage by q RT-PCR. The Cs NBS1 and Cs NBS2 genes were detected their expression differences between the high and low resistance tea plants, respectively. The main results are as follows:1. We used RNA-Seq to obtain three genome-wide expression profiles of a mechanically damaged plant, geometrid-damaged plant and undamaged control, and analyzed the differentially expressed unigenes bioinformatics after strategic transcriptomic comparisons, and finally tested the reliability of outcomes produced by RNA-Seq with q RT-PCR. Our research determined 2995 unigenes induced only by E. oblique oral secretion stimuli from 65548 unigenes. These unigenes were highly enriched in the plant hormone signal transduction pathways for insect resistance. For example the transcripts related to production of or responses to jasmonic acid(JA) and ethylene(ET) exhibited significant increases in expression after E. oblique damage. And we found brassinosteroids(BRs) can increase plant resistance to E. oblique stress.2. We filtered for 9 NBS-LRR-like resistance unigenes named Cs NBS1-9 through all assembly sequences with NBS-LRR protein annotations being aligned by the BLASTX against the NCBI non-redundant(NR) protein database and conserved domains being detected by the Conserved Domains software. The bioinformatics analysis for the coding amino acid sequences showed that, all the Cs NBSs contain the NBS domain of NBS-LRR protein family typical structure through SMART, MEME and COLIS softwares; the other domains were arranged significantly differently and of diverse protein length; the phylogenetic tree of Cs NBSs protein reflected Cs NBSs may be divided into TIR-NBS-LRR(TNL) and non-TIR-NBS-LRR(non-TNL) two groups, with Cs NBS1 and Cs NBS2 respectively as the TNL and CNL of non-TNL subfamilies sequences.3. The expression patterns of Cs NBS1 and Cs NBS2 in different resistance tea plants after E. oblique damage by q RT-PCR revealed that, Cs NBS2 of the high resistance tea plant increases the expression level while Cs NBS1 decreases the expression level, however the two genes of the low resistance one have a otherwise trend. The Cs NBS1 and Cs NBS2 genes expression differences between the high and low resistance tea cultivars showed that, the high resistance tea plants have a lower Cs NBS1 but higher Cs NBS2 expression level than the low resistance one, indicating Cs NBS1 and Cs NBS2 can work as potential resistance indicators.