Organ-specific gene expression and genetic transformation for improving rice

Abstract

Organ-specific expression of the genes isolated from the chloroplast genome of indica rice has been shown to involve quantitative and qualitative changes in mRNAs. This in turn depends largely on the quantity of the template and signal components such as calcium and protein phosphatases/kinases. To isolate nuclear genes and promoters specific to inflorescence and roots, organ-specific cDNA libraries were made from indica rice. These have either been employed for differential screening or cDNA clones have been randomly picked and tested for organ-specific expression. An analysis of such cDNAs has revealed that 12 cDNAs are new to rice and five of them do not show homology to any known sequence from the databases. Genomic clones of several have been isolated to delineate organ-specific promoters by employing the transgenic rice/tobacco system. An Agrobacterium-mediated high-frequency transformation system for elite indica variety Pusa Basmati 1 has been established. The system has been used to analyze the activity of a new promoter and to introduce agronomically useful genes in rice.