Roles of AGCVIII kinases in the hypocotyl phototropism of Arabidopsis seedlings (Plant Cell Physiol.)

Phosphorylation and de-phosphorylation are fundamental events for signal transduction. Phytohormone and light signaling are no exception in this case. Plants face towards light by creating lateral auxin gradient between exposed and shaded sides. This asymmetric auxin distribution is mediated through auxin transporter PIN-FORMED (PIN) proteins. One possible mechanism is the regulation of PIN protein through phosphorylation. In this study, they have studied AGCVIII kinase family (D6PK, phots, PID), known to regulate auxin transport activity via PIN phosphorylation. They have demonstrated that D6PK (D6 PROTEIN KINASEs) plays critical role in hypocotyl phototropism. Additionally, AGC1-12, another AGCVIII kinase, phosphorylates serine residues of PIN1 at hydrophilic loops and it shares the preferred phosphorylation site with D6PK. Taken together, D6PK and AGC1-12 play functionally important role for maintaining both phototropism and gravitropism in the hypocotyl by regulating PIN-mediated auxin transport. (Summary by Arif Ashraf) Plant Cell Physiol. 10.1093/pcp/pcy048