A novel histidine kinase gene, ZmHK9, mediate drought tolerance through the regulation of stomatal development in Arabidopsis

Plants have developed complex signaling networks to regulate biochemical and physiological acclimation, environmental signals were perceived and transmitted to cellular machinery to activate adaptive responses. Here, a novel drought responsive histidine kinase gene was identified and designated as ZmHK9. Under normal conditions, ZmHK9 was predominantly expressed in roots, and the roots of ZmHK9-OX transgenic lines are markedly hypersensitive to ABA and ethylene, as compare to wild type. Consistent with its expression induced by PEG and exogenous ABA treatment, promoter sequence of this gene possessed drought and ABA responsive element. Moreover, the transgenic plants were much less affected by drought stress and recovered quickly after rewatering, stomatal complex size and stomatal density in the transgenic plants are significantly smaller and lower than those of the wild-type plants. In addition, ABA induced stomatal closure and the stomatal aperture of ZmHK9-OX lines was smaller than that of wild type. Collectively, it can be concluded that ZmHK9 regulates root elongation, stomatal development and drought tolerance through ABA dependent signaling pathway in Arabidopsis.

► We clone the novel ZmHK9 gene in maize inbred line Zong31.
► ZmHK9 highly express in root and induced by PEG and exogenous ABA treatment.
► Transgenic Arabidopsis plants overexpressing ZmHK9 gene enhance drought tolerance.
► Guard cells from ZmHK9-OX plants are more sensitive to ABA-induced stomatal closure.
► Rate of water loss, stomatal density and complex size reduce in ZmHK9-OX plants.