Abstract
The two-component regulatory systems involving histidine-kinases (HK), which serve as signal receptors, are widespread signal transduction strategies in higher plants. In fact, HKs act as cytokinin receptors, which play crucial roles in hormone responses in Arabidopsis. It should also be emphasized that the plant two-component systems had evolved form the ones in prokaryotic bacteria. In fact, it was demonstrated that the Arabidopsis HKs (AHK2/3/4) are able to function as plant hormone cytokinin sensors in Esherichia coli. Hence, it is of interest to characterize the plant two-component systems from the evolutional viewpoint. In this respect, Physcomitrella patens is particularly interesting, because this species of moss is a basal lineage of land plants, having diverged before the acquisition of well developed vasculature. Here, we conducted genome-wide bio-informatics with special reference to the two-component systems-associated genes, including clock-associated ones, by adopting the genome databases of P. patens. Furthermore, we will provide experimental evidence for that this moss had a set of AHK2/3/4 homolog, which has an ability to act as cytokinin sensors in E. coli.
