Control of Circadian Rhythms and Photoperiodic Flowering by the <i>Arabidopsis GIGANTEA</i> Gene

TLDR

Plants regulate flowering in a day‑length–dependent manner, a key photoperiodic response. Loss‑of‑function mutations in GIGANTEA disrupt photoperiod‑dependent flowering, reduce circadian amplitude, shorten period, and alter light signaling, indicating GI’s essential role in the plant circadian feedback loop.

Abstract

Photoperiodic responses in plants include flowering that is day-length–dependent. Mutations in the Arabidopsis thaliana GIGANTEA ( GI ) gene cause photoperiod-insensitive flowering and alteration of circadian rhythms. The GI gene encodes a protein containing six putative transmembrane domains. Circadian expression patterns of the GI gene and the clock-associated genes, LHY and CCA1 , are altered in gi mutants, showing that GI is required for maintaining circadian amplitude and appropriate period length of these genes. The gi-1 mutation also affects light signaling to the clock, which suggests that GI participates in a feedback loop of the plant circadian system.