Abstract
Heading date 3a (Hd3a) protein in rice and its Arabidopsis ortholog FT are recently considered as the likely florigen, the crucial component of a long-distance flowering signal. Hd3a protein is generated at the leaf phloem tissue in flowering-promoting conditions, moves from leaves to apical meristem and causes flowering. Here we show overexpression of Hd3a in vasculature caused not only early heading but also high tillering, semi-dwarf, abnormal internode elongation and abnormal panicle architecture. Detailed observation revealed that high tillering phenotype is caused by outgrowth of axillary meristems. We show that Hd3a protein moves from leaf to the axillary meristems and induces meristem outgrowth. These data suggest that Hd3a/FT-like proteins may define the novel type of the mobile molecule that integrates the development between organs that sense and adapt the environment.
