Are there multiple circadian clocks in plants?

摘要

We have reported that Arabidopsis might have genetically distinct circadian oscillators in multiple cell-types. Rhythms of CHLOROPHYLL A/B BINDING PROTEIN2 (CAB2) promoter activity are 2.5 h longer in phytochromeB mutants in constant red light and incryptocromel cry2 double mutant (by4-1 fha-1) in constant blue light than the wild-type. However, we found that cytosolic free Ca~(2+) ([Ca~(2+)]_(cyt) ) oscillations were undetectable in these mutants in the same light conditions. Furthermore, mutants of CIRCADIAN CLOCK ASSOCIATEDl (CCAI) have short period rhythms of leaf movement but have arrhythmic [Ca~(2+)]_(cyt) oscillations. More important, the timing of cab 1-1 (tocl-1) mutant has short period rhythms of CAB2 promoter activity (-21 h) but, surprisingly, has a wild-type period for circadian [Ca~(2+)]_(cyt) oscillations (-24 h). In contrast, tocl-2, a TOCl loss-of-function mutant, has a short period of both CAB2 and [Ca~(2+)]_(cyt) rhythms (-21 h). Here we discuss the difference between the phenotypes of tocl-l and tocl-2 and how rhythms of CAB2 promoter activity and circadian [Ca~(2+)]_(cyt) oscillations might be regulated differendy.