It is not accidental that the members of the PRR family are transcribed from DNA to RNA at different times of day, suggesting that the protein products function in processes that are coordinated with diurnal events. Thus, one of the mechanisms of clock gene regulation is the control of transcription and accumulation of RNA transcripts. Other forms of regulation are post-translationalafter the clock gene proteins have been made. These proteins are translocated to different compartments to perform their functions, have phosphate groups attached to them to change their activity, or are marked for degradationall precisely timed for optimal function.
With mutant analyses, McClung and his coworkers have shown that the PRR genes do not act in isolation, but rather are integrated and overlapping in function. Double and triple mutants have effects that are not simply additive but are much larger than those of single mutants. This suggests that it is adaptive for plants to have a group of genes, each with a small effect, but when functionally linked with other genes, part of a precise mechanism capable of subtle and specific responses, like the interlocking wheels of a clock.
McClung and his colleagues are studying how such mechanisms could have evolved. Through sequence analysis of PRR7 in over 100 different cultivars of Arabidopsis, they have shown that the nucleotides in the gene's DNA are replaced at a significant ra
|Contact: C. Robertson McClung|
American Society of Plant Biologists