Circadian clock components in Arabidopsis I. The terminal flower 1 enhances the early flowering phenotype of a mutant, lhy cca1

Abstract

Two myb-related proteins, LHY and CCA1 are essential for circadian clock function in Arabidopsis. Double loss-of-function of lhy cca1 shows a photoperiod-insensitive phenotype and a shortened generation time under short-days (SDs). To understand the molecular mechanisms underlying early flowering of lhy cca1 mutants, we screened for mutations that enhanced the phenotype of lhy cca1 under SDs. Here we show that one of the enhancer mutations is a novel allele of a shoot-identity gene, terminal flower 1 (tfl1). Triple loss-of-function of lhy cca1 tfl1 causes precocious and ectopic expression of LFY and AP1 and dramatically reduces the generation time of Arabidopsis. The additive phenotype in lhy cca1 tfl1 may be due to convergence of the autonomous and photoperiod pathways. Reduction of generation time of crops is an important issue for molecular breeding. Our results highlight a possibility that combining loss-of-function of the circadian clock and one of the shoot-identity genes can be applied for the marker-assisted breeding to manipulate flowering time of crops. Copyright © 2005 The Japanese Society for Plant Cell and Molecular Biology.