Expression and functional analysis of rice genes involved in reproductive development and stress response

Abstract

The rice genome sequenced and annotated by the IRGSP has identified 37,544 protein-coding genes. In an effort to identify genes encoding transcription factors and signal transduction components, more than 7,000 genes belonging to 87 classes have been used to prepare a local database. Detailed analysis of genes for plant hormone response, CDPKs, C2H2 zinc-finger, and SET domain proteins unraveled interesting evolutionary aspects in relation to genes and the rice genome. A 51k microarray, SAGE analysis, and real-time polymerase chain reaction revealed differential expression of target genes during reproductive development and stress conditions. Several genes specific to reproductive floral organs and seed development have been identified. A large number of SAGE tags are observed from intergenic regions and antisense strands reflecting the unexplored transcription potential of the rice genome. Analysis of rice gene promoter activities has been undertaken in transgenic tobacco/Arabidopsis to demarcate regions conferring anther-/pollen-specific expression. OSISAP1, a gene coding for a stress-associated zinc-finger protein, and its promoter have been functionally validated in transgenic tobacco and rice. Genes for proteins interacting with OSISAP1 have also been found to be stress-inducible. Investigations on functional analysis of stress-responsive genes are in progress.