| Sorghum is the fifth most important cereal crop in the world,with rich genetic diversity and great potential to explore important genetic resources.Sorghum also is a diploid plant with a simple genome of about 730 MB in size,and it can be used as a model plant for studying C4 crops.With the continuous growth of the global population and the deterioration of environment degradation,sorghum has received broad attention from breeders in recent years because of its drought,hardiness and salt resistance,but during its growth,sorghum is often suffering from pests and pathogens.Anthracnose caused by the hemibiotrophic pathogen Colletotrichum sublineolum is one of the most destructive diseases of sorghum.Salicylic acid(SA)is a phytohormone essential for plant immunity;however,the role of SA in sorghum resistance to anthracnose has not been well explored.In this study,we found that Colletotrichum sublineolum infection induced the expression of SA-responsive genes and exogenous SA enhanced resistance to anthracnose in BTx623.To rule out the possibility that SA triggers anthracnose resistance in sorghum by its direct toxic function on pathogen,BTx623 was identified as a SA sensitive line and WHEATLAND as a SA insensitive line by SA-inhibiting sorghum growth.SA treatment could not induce anthracnose resistance in WHEATLAND indicating the endogenous SA signaling is required for SA-triggered resistance.By analyzing the transcriptome data of SA sensitive line and insensitive line after SA treatment,a total of 5355 SA-induced differentially expressed genes(DEGs)were detected in BTx623,while only 3444 DEGs were detected in WHEATLAND.Some DEGs were upregulated and downregulated in both BTx623 and WHEATLAND but the induction/repression of them were higher in BTx623 than in WHEATLAND.Transcriptome data further prove that BTx623 is a SA sensitive sorghum line,while Wheatland is a SA tolerant sorghum line.SA pretreatment regulated the expression of 2125 genes in BTx623 but only 524 genes in WHEATLAND during Colletotrichum sublineolum infection.The cutin,suberine and wax biosynthesis pathway involved in the plant immune response and the flavonoid biosynthesis pathway involved in anthracnose resistance were enriched in BTx623 specifically upregulated genes.Additionally,some immune-related genes and plant disease resistance genes(R genes)were only differentially expressed in BTx623.Since the sorghum inbred lines showed different sensitivity to SA,we detected the sensitivity of 299 sorghum inbred lines to SA and performed genome-wide association study(GWAS)to further exploring how SA regulates the resistance of sorghum to anthracnose.The results showed that a single nucleotide polymorphism(SNP)site located within the bHLH transcription factor SbMYC-coded gene was significantly associated with the sensitivity of sorghum seedlings to S A.This SNP site causes a missense mutation in the Leucine zippers(Zip)domain sequence of SbMYC.It has been reported that MYC transcription factors are critical to plant responses to SA,so this study intends to explore in depth the function of SbMYC in sorghum response to SA and anthracnose resistance.First,we studied the biological function of the SbMYC transcription factor by cloning it and transferring it into Arabidopsis myc2 mutants.The results showed that the SbMYCT form,which encodes protein consistent with the Zip functional domain site sequence in other species,could better complement the phenotype of Arabidopsis myc2 mutants.This shows that this missense mutation in SbMYC may affect its function and then causes the difference in SA sensitivity between different sorghum inbred lines.In this study,we want to further verify the function of the SbMYC gene by high expression and mutation of SbMYC in sorghum,and now we have obtained the T0 generation strain of the transgenic plants.This study will provide an important reference for more in-depth study of the gene function of sorghum on anthracnose resistance and future anthracnose resistance breeding. |
PDF Full Text Request