| Sesame（Sesamum indicum）stem rot,a destructive fungal disease caused by Macrophomina phaseolina（MP）,is a severe threat to the yield and quality of sesame.Up to now,many reports are focused on sesame germplasm resistance,epidemiology and control of sesame stem rot,while the molecular mechanism of the interaction between sesame and MP remains to be explained.Therefore,it is of great significance for sesame breeding and genetic improvement to explore the molecular mechanism of sesame resistance to stem rot and screen the candidate resistant genes against MP.In this study,the molecular mechanism of sesame resistance to MP was preliminarily explored by the analysis of the transcriptome data from disease-resistant（DR）sesame genotype Zhengzhi No.13 and disease-susceptible（DS）sesame genotype Ji 9014 at 0h,12 h,24 h,36 h and 48 h post MP inoculation.In addition,genes involved in the defence to MP were screened out and their functions need further verified.The main contents and results of this study are as follows:1.A set of 867 core genes induced under MP stress were revealed by comparative transcriptomics and they were enriched in GO terms such as ribosome-related processes,fruit ripening and regulation of jasmonic acid mediated signalling pathway.The genes which code for protein kinases,pathogenesis-related proteins,cytochrome P450 and peroxidase in the core gene set are closely related to plant resistance.Furthermore,52 genes expressed continuously and differentially between DR and DS were screened under MP press,which were enriched in GO terms such as response to abscisic acid,cell wall,hormone-mediated signalling pathway,response to hormone,defence response and signal transduction.It is indicated that the genes in these two sets have conjectural functions in the sesame defence against MP to some extent.2.Weighted gene co-expression network analysis（WGCNA）revealed the hub genes highly related to stem rot resistance in sesame,among which three genes encode leucine rich repeat receptor kinase-like（LRR-RLK）protein family,including LOC105160699,LOC105172070 and LOC110012469.It is indicated that LRR-RLKs may play an important role in the defense response of sesame to MP.In addition,some key transcription factors that play important roles in the defense response were detected in these hub genes,such as LOC105161270（GRAS）,LOC105173824（b HLH）and LOC105174354（MYB）.3.The molecular mechanism of sesame resistance against Macrophomina phaseolina was revealed via RNA-seq.All genes involved in the PTI and ETI were detected in this study.Among them,174 genes showed different expression patterns between DR and DS.These genes include PRRs and R genes that recognize pathogens,Ca2+influx process related genes and MAPK cascades related genes that phosphorylate and activate downstream genes such as Rbohs and genes related to hormone metabolism and transduction（JA/ET and SA）.Of note,most of the PRRs,Ca2+influx related genes and R genes were induced in DR,indicating stronger PTI and ETI were triggered in DR.Finally,the expression of genes related to JA/ET and SA biosynthesis and signalling transduction also showed differences among DR and DS,indicating that JA/ET and SA signalling transduction pathway are both crucial in sesame resistance to MP.4.Analysis of RNA-seq revealed that SiWAKL gene family can respond to MP stress in sesame.A total of 23 SiWAKLs on nine sesame linkage groups were identified.They can be divided into 8 groups and their molecular weight are 67.74 k Da-86.62k Da.GO annotation showed that SiWAKLs take functions in phosphorylation and signalling transduction on the cell membrane.It is worth noting that the expression of SiWAKL02 and SiWAKL10 were high an they can be induced observably in DR when inoculated with MP,while they showed no significant changes in DS.Additionally,SiWAKL02（LOC105162019）exists in 52-gene sets differentially expressed between DR and DS,indicating that SiWAKL02 may play an important role in sesame resistance to MP. |
