Peanut (Arachis hypogaea) transcriptome revealed the molecular interactions of the defense mechanism in response to early leaf spot fungi (Cercospora arachidicola)

Abstract

Cercospora arachidicola fungus is a causative agent of early leaf spot disease in peanut (Arachis hypogaea). However, little has been reported about the molecular interactions for defense mechanisms in the peanut plant against the fungal attack. In this study, we used RNA-Seq to analyse the expression profile of resistant (GPBD-4) and susceptible (JL-24) genotypes of peanut against C. arachidicola infection. A total of 91,734,735 raw reads were generated from RNA-Seq data. Differentially expressed genes (DEGs) were analysed for Gene Ontology to find essential genes responsible for defense mechanisms and to study their pathways by KEGG analysis. The resistant variety was able to withstand biotic stress due to exclusive up-regulation of defense-related genes (thaumatin, glutathione peroxidase, and cinnamyl alcohol dehydrogenase), while the susceptible variety was more prone to damage by infection due to down-regulation of genes including (F-box, cytochrome p450, Leucine-rich repeat protein kinase and terpene synthase) associated with a majority of biological function. RNA-Seq profile was validated by Reverse Transcriptase qPCR (RT-qPCR) technique, which showed a high correlation (R2 = 0.92) with the gene expression profile of RNA-Seq analysis. A total of 8591 EST-SSR markers were developed from the transcriptome library and 15 PCR primers based on microsatellite markers were used to validate SSR amplification. This study provides insight into the understanding of molecular interactions between plant and pathogen, and will also help to generate molecular markers for genetic mapping of peanut.