Molecular profiling of systemic acquired resistance (SAR)-responsive transcripts in sugarcane challenged with Colletotrichum falcatum.

Abstract

Red rot disease of sugarcane caused by Colletotrichum falcatum is one of the serious constraints affecting the productivity of the crop. The strategy of employing systemic acquired resistance (SAR) against red rot yielded consistently good results at field level. However, elucidation of genes involved in the induction of SAR continues to be a challenging area of research for a critical understanding of red rot disease resistance in sugarcane. Here, temporal expression of 22 putative defense-related genes were analyzed by semiquantitative reverse transcription-PCR (RT-PCR) in red rot-susceptible cultivar (CoC 671) with response to priming using various SAR inducers, viz. benzothiadiazole (BTH), salicylic acid (SA), and C. falcatum elicitor. Among the 22 genes studied, 12 transcripts were found to be differentially expressed, of which seven transcripts represent phenylpropanoid pathway and five transcripts represent resistant gene analogues (RGAs). Differentially regulated phenylpropanoid pathway genes such as cinnamic acid 4-hydroxylase, 4-coumarate:coenzyme A ligase, chalcone synthase, and chalcone reductase were reported to play a major role in the regulation of phytoalexin synthesis, whereas R genes such as NBS-LRR genes and basal layer antifungal peptide (BAF) genes were upregulated upon SAR induction in response to pathogen challenge. These upregulated genes presumably play a potential role in SAR induction and might contribute to defense against C. falcatum.