Abstract
In the Arabidopsis thaliana genome, there are at least 11 distinct Arabidopsis histidine kinases classified into two groups: the ethylene receptors consist of 5 members and the other six AHKs. Recently, it has been shown that ATHK1 and a cytokinin receptor CRE1/AHK4 can function as osmosensing receptors in yeast, here we further showed that AHK2 and AHK3 as well. However, the ethylene receptors do not. Expression of ATHK1, AHK2, AHK3 and AHK4 is induced by dehydration. Transgenic plants overexpressing ATHK1 have delay in bolting and display shorter inflorescence, however the morphological phenotype of the athk1 T-DNA insertion mutant is unchanged. Callus induction assay suggested that ATHK1 may also function as cytokinin receptor. Germination assays demonstrated that these 4 kinases may have important function in ABA and glucose signalings. Northern blot analysis of stress-inducible marker genes suggested that these kinases also play an important role in abiotic stress signaling.
