Molecular Genetic Approach for the Search of Florigen; Rice as an Example

Abstract

The study of genes involved in regulation of flowering time in rice started only recently. Comparative study of flowering time genes in rice, a SDP, and Arabidopsis, a LDP, indicates that they are highly conserved between the two species. The difference between rice and Arabidopsis is generated by the difference in the regulation of FT by CO, Hd3a by Hd1 in rice. A genetic model suggests that genes are conserved but their regulation is different between them.
Our study on Hd3a promoter activity by the use of Hd3a::gus fusion indicates it is active in the vascular tissue of leaf. The Hd3a-GFP fusion gene driven by the phloem-specific rolC promoter caused early flowering in rice. These results suggest a possibility that Hd3a protein might function as a florigen. In this talk we present results of our studies on Hd3a gene and its protein product.