Genetic interactions between diverged alleles of <i>Early heading date 1</i> (<i>Ehd1</i>) and <i>Heading date 3a</i> (<i>Hd3a</i>)<i>/ RICE <scp>FLOWERING LOCUS</scp> T1</i> (<i><scp>RFT</scp>1</i>) control differential heading and contribute to regional adaptation in rice (<i>Oryza sativa</i>)

Abstract

Summary Initiation of flowering, also called heading, in rice ( Oryza sativa ) is determined by the florigens encoded by Heading date 3a ( Hd3a ) and RICE FLOWERING LOCUS T1 ( RFT 1 ). Early heading date 1 ( Ehd1 ) regulates Hd3a and RFT 1 . However, different rice varieties have diverged alleles of Ehd1 and Hd3a/ RFT 1 and their genetic interactions remain largely unclear. Here we generated three segregating populations for different combinations of diverged Ehd1 and Hd3a/RFT1 alleles, and analyzed their genetic interactions between these alleles. We demonstrated that, in an ehd1 mutant background, Hd3a was silenced, but RFT 1 was expressed (although at lower levels than in plants with a functional Ehd1 ) under short‐day ( SD ) and long‐day ( LD ) conditions. We identified a nonfunctional RFT 1 allele ( rft1 ); the lines carrying homozygous ehd1 and Hd3a/rft1 failed to induce the floral transition under SD and LD conditions. Like Hd3a, RFT 1 also interacted with 14‐3‐3 proteins, the florigen receptors, but a nonfunctional RFT 1 with a crucial E105K mutation failed to interact with 14‐3‐3 proteins. Furthermore, analyses of sequence variation and geographic distribution suggested that functional RFT 1 alleles were selected during rice adaptation to high‐latitude regions. Our results demonstrate the important roles of RFT 1 in rice flowering and regional adaptation.