Isolation and expression analysis of defense-related genes in sorghum–Colletotrichum sublineolum interaction

Abstract

Anthracnose caused by the fungal pathogen Colletotrichum sublineolum is one of the most devastating diseases in sorghum. To better understand the molecular basis of sorghum–C. sublineolum interactions, a cDNA library enriched for defense response mRNAs was constructed by suppression subtractive hybridization (SSH) of inoculated mesocotyl tissues of a resistant cultivar (cv. DK18) vs. non-inoculated samples. A total of forty pathogen-inducible genes involved in cell rescue and defense, signal transduction, abiotic stress, secondary metabolism and protein degradation were identified, implicating a complex defense response to the anthracnose pathogen. Gene expression analyses demonstrated that all the genes were induced by C. sublineolum and two non-host pathogens. However, the expression patterns of nineteen genes suggested that they are regulated differently during host and non-host defense responses in sorghum. Genes encoding an ABA-responsive protein, a leucine-rich repeat protein, a flavonoid 3′-hydroxylase and a glutathione S-transferase were induced in the resistant cultivar but their expression was hardly detected in susceptible plants, suggesting that they play significant roles in anthracnose resistance. This study provides an efficient resource for sorghum defense-related gene discovery that may further enhance the investigation of molecular mechanisms of defense responses in sorghum toward fungal pathogens.