Isolation of novel gain- and loss-of-function alleles of the circadian clock gene LATE ELONGATED HYPOCOTYL (LHY) in Arabidopsis

Abstract

In Arabidopsis, two myb-related proteins, LATE ELONGATED HYPOCOTYL (LHY) and CIRCADIAN CLOCK ASSOCIATED 1 (CCA1), play key roles in the control of circadian rhythms. Photoperiodic flowering and elongation of hypocotyls are regulated by a circadian clock. Here, we report the isolation and characterization of a novel deletion allele (lhy-14) and a gain-of-function allele (lhy-2) of lhy. Based on long hypocotyl and late flowering phenotypes under long days, lhy-2 was isolated as an intragenic suppressor of lhy-12, one of the loss-of-function alleles of lhy. Although the lhy-12 mRNA has a 19-bp truncation, we found that this was not caused by a deletion in the LHY but by a point mutation. We propose a model explaining the loss-of-function of LHY in lhy-12 and the partial suppression of the lhy-12 phenotype by lhy-2, by the abnormal splicing of LHY mRNA.