Differential gene expression for bacterial wilt incidence in tomato ( Solanum lycopersicum L.) revealed by cDNA-AFLP analysis

Abstract

Bacterial wilt (BW) incited by Ralstonia solanacearum (Smith) – a soil-borne bacterium is a devastating disease of tomato cultivation in the tropical and subtropical humid regions of the world. The disease is widespread in India and is the main limiting factor for tomato cultivation in Kerala. Experiments were designed to trigger the pathogen-challenged disease responses in both susceptible (H24) and resistant (Anagha) tomato genotypes and monitor the expression of stress induced genes or gene fragments at the transcript level. cDNA-AFLP (Amplified Fragment Length Polymorphism) analysis was performed with the cDNA synthesized from resistant and susceptible genotypes at second and fifth days after inoculation. A total of 763 transcript-derived fragments (TDFs) were analyzed from 21 primer sets and 58 TDFs were detected to be differentially expressed during pathogen challenge. Upon cloning and sequence analysis of these differentially expressed TDFs, two of them showed homology to plant retrotransposons-putative gag-pol polyproteins and three-showed homology to aspartate kinase/homoserine dehydrogenase. Two TDFs have sequence identity to genes known to have function in plant defense. Three-showed homology to Secretin proteins. The results indicated the involvement of several such factors in plant–pathogen interactions. The expression of transcripts was further validated through quantitative real-time PCR. The present study would be helpful in elucidating the molecular basis of the infection process and identifying the defense genes that can be targeted for incorporating bacterial wilt resistance.