Abstract
Greening of etiolated seedlings is an important process of photomorphogenic responses. The chlorophyll synthesis under light must be finely controlled because certain intermediates of chlorophyll synthesis act as oxidative reactants, which might cause dangerous effects on plants. However, the regulatory mechanism underlying the chlorophyll synthesis during de-etiolation (or greening) is not fully understood. In this respect, it was recently reported that a phytochrome-interacting bHLH transcription factor, name PIF1, serves as a negative regulator of the chlorophyll synthesis in etiolated seedlings. PIF1 is interesting because this bHLH factor turned out to be identical to PIL5, which we previously identified as a factor that directly interacts with the Arabidopsis clock-component PRR1/TOC1 in yeast two-hybrid analyses. This fact led us to envisage that the clock-associated factors, such as PRRs and CCA1, might closely implicated in the control of the chlorophyll synthesis. Here we report several lines evidence that strongly support this intriguing hypothesis.
