Comparative Transcriptome Analysis Reveals the Molecular Response of Sesame Capsules to Infection by Alternaria alternata.

The genus Alternaria (Nees) is a major phytopathogen responsible for diseases. In Sesame, Alternaria alternata infects capsules during the rainy season (August-September) in Northeast China, inducing lesion expansion and compromising seed yield and quality. To investigate the molecular response of Sesame to Alternaria alternata infection, transcriptome analyses of "Liaozhi No. 9" were conducted on the pericarp and seeds of sesame capsules before and after A. alternata infection. For the data quality control, the GC content and the proportion of Q30 bases indicated that the sequencing quality was good. The correlation analysis and principal component analysis (PCA) among sample groups demonstrated that the biological replicates had high similarity and there were obvious differences between groups. Differential gene expression analysis was performed using DESeq2. There were 5892 and 9120 differentially expressed genes in the pericarp and seeds, respectively, and among them, 2788 were the same differential genes. GO functional annotation was carried out on the differentially expressed genes, and the results showed that the differential genes were mainly enriched in biological processes (cellular processes, metabolic processes), molecular functions (catalytic activity and binding), and cellular components (cellular anatomical entities and intracellular components). KEGG metabolic pathway analysis revealed that metabolic pathways such as plant hormone signal transduction and plant-pathogen interaction were enriched after the infection of A. alternata. The genes in the jasmonic acid pathway (MYC2) and in the salicylic acid pathway (NPR1 and TGA) of the plant hormone signal transduction pathway were induced after A. alternata infection. Meanwhile, the genes in plant-pathogen interaction pathway, such as CML, CDPK and CNCGs were also induced after the infection. This study indicates that sesame capsules respond to the infection of Alternaria alternata through the genes in the plant hormone signal transduction pathway and the plant-pathogen interaction metabolic pathway, providing a theoretical basis for the subsequent research on sesame disease-resistant breeding and its molecular mechanism.