Molecular profiling of red rot resistance in sugarcane

Abstract

We have undertaken detailed studies on the mechanism of red rot resistance in sugarcane. Our initial studies based on biochemical tools, identified the possible involvement of oxidative enzymes and red rot pigments in disease resistance. Further studies revealed the role of pathogenesis-related (PR) proteins and 3-deoxyanthocyanidin phytoalexins in red rot resistance. Our recent genomic studies involving semiquantitative RT-PCR, differential display (DD)-RT-PCR and subtractive libraries identified many transcripts involved in red rot resistance. Differential accumulation of transcripts potentially involved in the flavanoid biosynthetic pathway genes was established and further confirmed the role of sugarcane phytoalexins in red rot resistance. Similarly the role of PR- proteins like chitinase, -1,3-glucanase and TLPs in red rot resistance was established at the transcript level. Differential accumulation of chitinase, -1,3-glucanase was further validated by qPCR and northern blot analysis. In subtractive libraries, ~400 transcripts associated with signal transduction, defense, transcription factors, energy metabolism, carbohydrate metabolism and cell structure maintenance were obtained. Using RACE technique, we have isolated full length sequences of the following four genes putatively involved in red rot resistance viz. 14-3-3 like protein, chitinase, xylanase inhibitor and basal antifungal peptide. Studies on regulation of five major families/classes of defense related transcription factors (TFs) revealed earlier induction of 14 red rot pathogen responsive TFs in resistant variety. Also to identify specific proteins involved in host resistance, proteomic approach has been attempted by optimizing sample preparation from stalk tissues, 2-D electrophoresis (2-DE), downstream processing of identified spots by MS analysis and bioinformatics. About 125 up/down regulated proteins were characterized by peptide mass finger printing, some of the identified important proteins were putative callose synthase, R2R3-MYB transcription factor MYB6, p-coumarate 3-hydroxylase, PrLTP1 and PISTILLATA-like protein.