Switching genetic effects of the flowering time gene <i>Hd1</i> in LD conditions by <i>Ghd7</i> and <i>OsPRR37</i> in rice

Abstract

Flowering time control in plants is a major limiting factor on the range of species. Day length, perceived via the photoperiodic pathway, is a critical factor for the induction of flowering. The module of <i>GIGANTEA (GI)</i>-<i>CONSTANS (CO)</i>-<i>FLOWERING LOCUS T</i> in the long day (LD) plant <i>Arabidopsis</i> is conserved in diverse plant species including the short day (SD) plant rice, where this module comprises <i>OsGI-Heading date 1</i> (<i>Hd1</i>)-<i>Heading date 3a</i>. <i>Hd1</i>, the rice ortholog of <i>Arabidopsis CO</i>, has dual functions in the regulation of flowering time, promoting flowering in SD conditions and delaying it in LD conditions. We herein show genetic interactions among three LD repressor genes: <i>Hd1</i>, <i>Grain number</i>, <i>plant height and heading date 7</i> (<i>Ghd7</i>), and <i>Oryza sativa Pseudo-Response Regulator37</i> (<i>OsPRR37</i>). Genetic analyses, including segregation analyses, evaluations of near isogenic lines, and transformation for flowering time demonstrated that <i>Hd1</i> promoted flowering time in inductive SD and non-inductive LD conditions in genetic condition of loss-of-function <i>Ghd7</i> and <i>OsPRR37</i> (<i>ghd7osprr37</i>) in rice. Functional <i>Ghd7</i> or <i>OsPRR37</i> may switch the genetic effects of <i>Hd1</i> from the promotion to the delay of flowering times in LD conditions.