<i>Hd1</i>, a Major Photoperiod Sensitivity Quantitative Trait Locus in Rice, Is Closely Related to the Arabidopsis Flowering Time Gene <i>CONSTANS</i>

TLDR

We suggest that Hd1 promotes heading under short‑day conditions and inhibits it under long‑day conditions. High‑resolution mapping of 1,505 segregants defined a ~12‑kb candidate region for Hd1. Hd1, a ~12‑kb QTL homologous to Arabidopsis CONSTANS, was identified by map‑based cloning, shown to be allelic to se1 mutants, functionally validated by complementation, and its expression is largely photoperiod‑independent.

Abstract

A major quantitative trait locus (QTL) controlling response to photoperiod, Hd1, was identified by means of a map-based cloning strategy. High-resolution mapping using 1505 segregants enabled us to define a genomic region of ∼12 kb as a candidate for Hd1. Further analysis revealed that the Hd1 QTL corresponds to a gene that is a homolog of CONSTANS in Arabidopsis. Sequencing analysis revealed a 43-bp deletion in the first exon of the photoperiod sensitivity 1 (se1) mutant HS66 and a 433-bp insertion in the intron in mutant HS110. Se1 is allelic to the Hd1 QTL, as determined by analysis of two se1 mutants, HS66 and HS110. Genetic complementation analysis proved the function of the candidate gene. The amount of Hd1 mRNA was not greatly affected by a change in length of the photoperiod. We suggest that Hd1 functions in the promotion of heading under short-day conditions and in inhibition under long-day conditions.