Abstract
LHY and CCA1 play central roles in the control of circadian rhythms in Arabidopsis. Loss-of-function of LHY and CCA1 genes (lhy;cca1) affects both flowering time and organ elongation in a photoperiod dependent manner. To investigate roles of molecular interactions between the endogenous circadian clock function and exogenous stimuli such as light/dark cycles in the control of photoperiodic flowering responses, genetic screening of enhancer mutations of the late flowering and semi-dwarf phenotype of the lhy;cca1 were performed. Seven enhancers were isolated and named petanko 1-7 (pta1-7). The pta7 mutation was identified as a novel gene by map-based cloning. Genetic screening of suppressor mutants of pta7 by EMS-mutagenesis has been performed. Yeast two-hybrid screening has identified several proteins (IF1, 2 and 3) that interact with PTA7. IF1 has been reported to control flowering via expression of a floral repressor FLC. IF2 has high homology to floral regulators in reported rice and maize. IF3 is a clock-controlled gene and co-expressed with LHY and CCA1, suggesting that LHY/CCA1-IF3-PTA7-IF1-FLC and IF2 may play a key role in the clock-associated control of flowering time.
