Abstract
One core group of clock components in Arabidopsis that controls the pace of the central oscillator is comprised of five PRR proteins whose biochemical function in the clock remains unclear. The PRRs are related to Response Regulators (RRs) of His-Asp phospho-relay signal transduction systems. We have identified and characterized genes encoding PRR homologs from Physcomitrella (Designated as PpPRR1, PpPRR2, PpPRR3 and PpPRR4).
It should be noted that the Arabidopsis PRRs lack phospho-accepting aspartate
(D) residue.Instead, each pesudo-receiver has a glutamate (E) residue at this particular position. Interestingly, Physcomitrella PRR does not show this property, instead all PpPRRs retain the aspartate (D) at the potential phosphorylation site.
Expression of PpPRRs under DD, LL and LD conditions shows circadian, arrhythmic and diurnal pattern respectively. These data have allowed us to interpret how plant PRRs evolved during evolution.
