Abstract
In A. thaliana, His-Asp phosphoerelay is involved in both the cytokinin- and ethylene-dependent signal transduction pathways, in which certain His-kinases particularly act as cytokinin-receptors or ethylene-receptors. Among 11 His-kinase-related proteins, 8 of them are directly implicated in either cytokinin or ethylene signaling. But, the remaining three HKs are less characterized. Here we clarified an interesting aspect of physiological functions of the least characterized one, named AHK5 (also known as CKI2). Three independent ahk5 T-DNA insertion mutant lines were established in the hope of revealing a common phenotype for all of them. The results suggested that AHK5 His-kinase regulates root elongation through an ETR1-dependently integrated abscisic acid (ABA) and ethylene signaling pathway. This new function of AHK5 will be discussed in the context of canonical signaling pathways of ABA and/or ethylene, such as those during germination and/or triple responses.
