Transcriptome of Pigeonpea Roots under Water Deficit Analyzed by Suppression Subtractive Hybridization

Abstract

Pigeonpea ( Cajanus cajan (L) Millsp.) is a drought tolerant legume widely gr own in the arid and semi-arid tropics of the world which posse sses a deep and extensive root system that succors a number of important physiological an d metabolic functions to cope with drought. Application of available functional genomi cs approaches to improve productivity under water deficit requires a better understanding of the mechanisms involved during pigeonpea’s response to water defic it stress. In order to identify the genes associated with water deficit in pigeonpea, Suppres sion Subtractive Hybridization cDNA library was constructed from polyethylene glycol-in duced water deficit young root tissues from pigeonpea and 157 high quality ESTs were gener ated by sequencing of 300 random clones which resulted in 95 unigenes comprising 37 contigs and 58 singlets. The cluster analysis of ESTs revealed that the majority of the genes had significant similarity with known proteins available in the databases along wit h unique and hypothetical/uncharacterized proteins. These differ ential ESTs were characterized and genes relevant to the specific physiological proces ses were identified. Northern blot analysis revealed the up regulation of ornithine am inotransferase, cyclophilin, DREB and peroxidase. The differentially expressed sequences are conceived to serve as a potential source of stress inducible genes of the water defic it transcriptome and hence may provide useful information to understand the molecular mech anism of water deficit management in legumes. Keywords : cDNA, drought, PEG, Polyethylene glycol.