Understanding the genetic and epigenetic architecture in complex network of rice flowering pathways

Abstract

Although the molecular basis of flowering time control is well dissected in the long day (LD) plant Arabidopsis, it is still largely unknown in the short day (SD) plant rice. Rice flowering time (heading date) is an important agronomic trait for season adaption and grain yield, which is affected by both genetic and environmental factors. During the last decade, as the nature of florigen was identified, notable progress has been made on exploration how florigen gene expression is genetically controlled. In Arabidopsis expression of certain key flowering integrators such as FLOWERING LOCUS C (FLC) and FLOWERING LOCUS T (FT) are also epigenetically regulated by various chromatin modifications, however, very little is known in rice on this aspect until very recently. This review summarized the advances of both genetic networks and chromatin modifications in rice flowering time control, attempting to give a complete view of the genetic and epigenetic architecture in complex network of rice flowering pathways.

Figure 1

Comparison of core-flowering-pathways in rice and Arabidopsis. OsGI/GI-Hd1/CO-Hd3a/FT pathway is conserved between rice and Arabidopsis. CO. accelerates flowering under LD, however, Hd1 promotes flowering under SD and represses it under LD. Besides, Ghd7 and Ehd1 in rice, and FLC in Arabidopsis are unique flowering integrators, respectively. FLC and Ghd7 are major flowering suppressors, while Ehd1 acts as a flowering promoter

Figure 2

Complex flowering time control network in rice. Rice flowering network is formed by two florigen genes Hd3a and RFT1, and four regulation modules, including Hd1-dependent pathway, Ehd1-dependent pathway, crosstalk between Hd1 and Ehd1 pathway, and flowering regulators independent of Hd1 and Ehd1. The first three signals come together to regulate Hd1 and Ehd1 and affect florigen gene expression; the last module may directly control the expression of florigen genes independent of Hd1 and Ehd1. Besides, expressions of Ehd3, RID1, OsMADS50, Hd3a, and RFT1 can be affected by H3K36me2/3; OsLFL1 and OsLF transcriptions can be mediated by H3K27me3. Finally, all those florigen signals are transported from leaves to SAM and trigger flowering transition there. All the gene names for short are showed in Table 1