Research On Gene Expression Profile Of Nitric Oxide Participating In Low Temperature-Inhibited Pollen Tube Growth In Camellia Sinensis

Tea plant[Camellia sinensis(L.)0.Kuntze]is an important economic crop in China.As a perennial evergreen woody plant,it is distributed from tropics to temperate zone,but low temperatures limit higher latitudes development in tea plants.Therefore,the research on the mechanism of low temperature tolerance in tea plants has received more and more attention.The regulation mechanism is very complicated in tea plants under low temperature.In recent years,with the application of high-throughput sequencing technology in botany,the cold resistance mechanism has made important progress in tea plant vegetative organs(leaf).However,there are few studies on the cold resistance mechanism in tea plant reproductive organs(pollen tube).Current studies have demonstrated that nitric oxide(NO),a broad-spectrum signal molecule,plays a negative regulatory role in response to low-temperature stress in tea pollen tubes growth.Therefore,in order to revealing the mechanism of NO signaling involved in pollen tube growth under low temperature.this study used the RNA-Seq to perform transcriptome sequencing of tea pollen tubes under 25℃(CK),4oC(LT),and NO(NO)treatment,including comparative analysis and functional annotation in every transcripts databases.Subsequently,the CK,LT,and NO transcripts were compared and screened for CK-VS-LT,CK-VS-NO and LT-VS-NO differentially expressed genes(DEGs)according to the screening criteria of|log2Ratio|>1 and probability>0.7.Finally,the differential genes of CK-VS-LT and CK-VS-NO DEGs were classified and analyzed.The main results are as follows:1.By annotating the function of Unigenes in tea pollen tube transcriptome,the annotation of six databases NR,NT,Swiss-Prot,KEGG,COG,GO library are 33716,31957,21494,20425,13029 and 26422 Unigenes,respectively.A total of 36097 Unigenes are annotated in six databases.There were 34776 coding protein box(CDS)aligned to the protein library by predicted CDS,including 33749 known and 1027 predicted CDSs.The results of CDSs annotations involved in all aspects of plant growth and development.According to the NR annotation results,it is found that there is a close relationship between C.sinensis and Vitis vinifera.These annotation results provide a large number of candidate genes for the molecular mechanism of tea pollen tube elongation,and provide a basis study of tea pollen tube under low temperature.2.766 and 497 DEGs are obtained by screening CK-VS-LT and CK-VS-NO,respectively.We obtained the related of DEGs that NO participate in tea pollen tubes growth under low temperature through further classification and analysis CK-VS-LT and CK-VS-NO DEGs,including plant hormone metabolism and signaling pathways,transcription factors(TFs),vesicle polarized trafficking,cell wall biosynthesis,the ubiquitination machinery of the ubiquitin system and species-specific secondary metabolite pathways.Combining with previous studies and our resultes,we speculated a potential signaling pathway model that NO is involved in tea pollen tube response to low temperature,Plant hormone signaling pathways(ABA,BRs,ET and auxin)respond to pollen germination and tube elongation at low temperature,and then TFs(MYB,ZFP,CAMTA and MADS-box)modulated relevant proteins expression.MADS-box may also act directly on the NO anabolic pathway,which in turn regulates the NO content in tea pollen tube.Meanwhile,the UPS(E3s,26S proteasome,U-box and BTB/POZ)probably involves in affecting pollen germination and tube growth in response to low-temperature stress by modulating the posttranslational proteins levels.Additionally,Ca2+ gradielt,vesicle polarized trafficking as well as cell wall biosynthesis might participate in pollen tube elongation under low-temperature stress through the NO signaling pathway by CAMTA,PI4K and COBRA-like genes.In summary,this study used RNA,seq technology to explore the potential signal transduction mechanism of NO involved in tea pollen tube growth under low temperature.The results not only enrich the tea plant transcriptome data resources,but also provide basic data for the molecular mechanism of NO response to low temperature in tea plants.