Authors: THANGAVELU RAMAN, VARUN GOPALAKRISHNAN, GANGA DEVI PERUMAL
Abstract: Identification of defense-related genes in the host is one of the most essential steps in understanding disease resistance mechanisms in plants. In this study, a suppression subtractive hybridization (SSH) library was constructed to study differential gene expression in banana plants mediated through a Fusarium wilt pathogen (Fusarium oxysporum f.sp cubense - Foc) and its interaction with the Foc effective biocontrol agent Trichoderma asperellum (prr2). Here cDNAs from the roots of banana cv. Grand Naine infected by Foc were used as the driver and cDNAs from Foc + T. asperellum inoculated banana plants as the tester population. After hybridization and cloning, an EST library of 300 nonredundant clones was obtained. Based on sequence analysis and a homology search in the NCBI database, the clones were assigned to different functional categories. The expression patterns of six selected defense-related genes, namely endochitinase, polyubiquitin, calmodulin binding protein, pleotropic drug resistant gene, isoflavone reductase, and mannose binding lectin, were analyzed through quantitative real-time PCR in Foc alone inoculated and Foc + T. asperellum inoculated banana plants. It was observed that the expression of these genes during initial progression of disease was higher in Foc + T. asperellum inoculated plants as compared to Foc alone inoculated plants. Our results constitute a step toward a better understanding of the role of mycoparasitic T. asperellum in plant defense during its interaction with Foc in the susceptible banana cultivar Grand Naine.
Keywords: Foc-biocontrol interaction, Fusarium oxysporum f. sp. cubense, Musa defense genes, suppression subtractive hybridization
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