Hd1 — Oryza sativa Japonica

Summary

Rice gene Hd1 (also known as BBX7, COL9, and other synonyms) on chromosome 6 encodes a transcription factor with DNA-binding, zinc-binding, and NAD ADP-ribosyltransferase activities, belonging to the CONSTANS-like family with B-box and CCT domains. Hd1 is associated with photoperiodic flowering regulation, including upregulation under short days and downregulation under long days, as well as circadian rhythm, oxidative stress responses, and hormone signaling pathways involving jasmonic acid, ethylene, and salicylic acid. The gene has been linked to blast resistance, grain number, grain yield, grain quality, amino acid content, panicle traits, and heading date. Additional associations include root development, spikelet number, plant height, UV-B sensitivity, and stress tolerance traits such as freezing tolerance and disease resistance. Studies of related genes in other species connect the family to flowering time, oxidative stress tolerance, and root growth.