Transcriptional analysis and histochemistry reveal that hypersensitive cell death and H2O2 have crucial roles in the resistance of tea plant (Camellia sinensis (L.) O. Kuntze) to anthracnose

Anthracnose causes severe losses of tea production in China.Although genes and biological processes involved in anthracnose resistance have been reported in other plants,the molecular response to anthracnose in tea plant is unknown.We used the susceptible tea cultivar Longjing 43 and the resistant cultivar Zhongcha 108 as materials and compared transcriptome changes in the leaves of both cultivars following Colletotrichum fructicola inoculation.In all,9015 and 8624 genes were differentially expressed between the resistant and susceptible cultivars and their controls(0 h),respectively.In both cultivars,the differentially expressed genes(DEGs)were enriched in 215 pathways,including responses to sugar metabolism,phytohormones,reactive oxygen species(ROS),biotic stimuli and signalling,transmembrane transporter activity,protease activity and signalling receptor activity,but DEG expression levels were higher in Zhongcha 108 than in Longjing 43.Moreover,functional enrichment analysis of the DEGs showed that hydrogen peroxide(H2O2)metabolism,cell death,secondary metabolism,and carbohydrate metabolism are involved in the defence of Zhongcha 108,and 88 key genes were identified.Protein–protein interaction(PPI)network demonstrated that putative mitogen-activated protein kinase(MAPK)cascades are activated by resistance(R)genes and mediate downstream defence responses.Histochemical analysis subsequently validated the strong hypersensitive response(HR)and H2O2 accumulation that occurred around the hyphal infection sites in Zhongcha 108.Overall,our results indicate that the HR and H2O2 are critical mechanisms in tea plant defence against anthracnose and may be activated by R genes via MAPK cascades.

Genome-wide identification and expression profiling reveal the diverse role of Methyl-CpG-binding domain proteins in tea plant Camellia sinensis

Methyl-CpG-binding domain(MBD)proteins are important DNA methylation readers that recognise methylated CpG sites and recruit histone deacetylase(HDAC)complexes and chromatin remodelling factors,leading to chromatin compaction,gene transcription,and genome integrity.Currently,MBD genes have only been identified in a few plant species and their structure and function in tea plants(Camellia sinensis)are unknown.In this study,16 C.sinensis MBD genes(CsMBD)were identified on a genome-wide level and classified into eight classes.The CsMBD genes were mapped on nine chromosomes in tea plants,and nine pairs of CsMBD genes existed.Based on conserved domain analysis,all of the identified CsMBD proteins contained at least one MBD domain.Expression analyses showed that CsMBD genes were expressed in tissue-and organ-specific patterns.We investigated the expression patterns of CsMBD genes in response to abiotic and biotic stresses and during different plant growth and development stages.Multiple pthytohormone and stress-related cis-acting was evaluated in their promoter region,such as GGTCA,TGACG,ABRE and LTR.Specific CsMBD genes were associated with environmental stresses and developmental stages,with little overlap.Overall,our findings reveal the diverse roles of CsMBD genes under different stress and developmental conditions,highlighting candidate genes for further functional studies on tea plants.

iTRAQ-based quantitative proteomic analysis of tea plant(Camellia sinensis(L.)O.Kuntze)during cold acclimation and de-acclimation procedures

To gain a better understanding on the mechanism of cold acclimation in tea plant[Camellia sinensis(L.)O.Kuntze]at the proteome level,an iTRAQ based quantitative proteome analysis was carried out to identify differentially accumulated proteins in the mature leaves which were collected at non-acclimated(NA),fully acclimated(CA)and de-acclimated(DA)stages.407 and 477 proteins identified from CA and DA showed significant abundance changes(at 95%confidence)compared with NA,respectively.Moreover,251 protein species changed their abundance in DA compared with CA.Those differential abundance protein species were mainly involved in metabolism,cell wall,photosynthesis,energy,protein synthesis,antioxidation,carbohydrate metabolic process and binding,and mapped to the pathways of biosynthesis of secondary metabolites,microbial metabolism in diverse environment,ribosome,metabolic pathway,sugar metabolism,protein processing,photosynthesis,and plant-pathogen interaction pathway.However,no significant correlation was detected between the identified proteins and cognate gene transcript levels by correlation analysis and qRT-PCR analysis.This study presents a comprehensive proteome in mature leaves at different cold acclimation status and provides new insights into cold acclimation mechanisms in tea plants.