The warming of overall climate requires to breed plant cultivars
tolerant to extreme osmotic tolerance, e.g. to high salt concentration in order to
improve their chance to survive deleterious effects of abiotic stress conditions. Our
initial aim is to isolate and characterize abiotic stress response regulatory genes
arisen from Arabidopsis thaliana which is known as a model species for such
investigations in higher plant. For this reason, a Ser/Thr protein kinase, the CRK5
was chosen. The CRK5 protein kinase is partly functionally characterized
exhibiting a role in the regulation of gravitropic responses of Arabidopsis thaliana
roots (Rigó et al., 2013). The CRK5 is a plasma membrane associated kinase that
forms U-shaped patterns facing outer lateral walls of root epidermis cells. The
CRK5 phosphorylates the hydrophilic loop of the auxin efflux transporter PIN2 in
vitro. Thus, delayed gravitropic response of crk5 mutant reflects defective
phosphorylation of PIN2 and deceleration of its brefeldin sensitive membrane
recycling. Recently, we have been investigating the regulatory role of CRK5
protein kinase under osmotic (salt) and oxidative (hydrogen peroxide) stresses. The
aim was to gather additional information regarding its role in the regulation of
responses to either high salinity or oxidative stress, and consequently, regarding the
impact on the auxin biosynthesis, transport and signaling. CRK protein kinase is
hypothesized to be involved in the regulation of the effect of reactive oxygen
species (ROS, e.g. hydrogen peroxide)