Abstract
Circadian clock in higher plants regulates various phenomena such as flowering, stomatal opening, and organ elongation. Two related myb proteins, LATE ELONGATED HYPOCOTYL (LHY) and CIRCADIAN CLOCK ASSOCIATED 1 (CCA1) play key roles in the clock-controlled processes such as regulation of flowering time and organ elongation in Arabidopsis thaliana. Recently, we have found that mutations in these two genes (lhy;cca1) affected both chlorophyll content and chlorophyll a/b ratio under different photoperiodic conditions. To understand a molecular mechanism underlying the clock-controlled regulation of chlorophyll, genetic analysis was performed and chlorophyll contents and a/b ratio of lhy;cca1 and control plants were compared.
Under different photoperiods, the amount of chlorophyll was almost constant in wild-type plants. By contrast, the chlorophyll content of lhy;cca1 was highly affected by length of light period. In addition, the ratio of chlorophyll a/b was altered in lhy;cca1 under the different photoperiods. We identified several mutations that suppressed the phenotypes of lhy;cca1. Hypothetical models to explain the phenotypes of lhy;cca1 will be discussed.
