PID/WAG-mediated phosphorylation of PIN3 mediates polarity switches during gravitropism (Sci Reports)

Auxin distribution depends on the polar localization of PIN-FORMED or PIN proteins. Based on different development and environmental stimuli, PIN proteins switch polarity to redirect the auxin flux. Additionally, phosphorylation of PIN is required for its function. For instance, PIN3 phosphorylation is required for PIN3 polarization and hypocotyl gravitropic response. Grones et al. showed that PID kinase is involved in the gravitropism and gravity-induced PIN3 relocation in root and hypocotyl. Downregulation of PID/WAGs increases gravity-induced PIN3 relocation and consequently gravitropic bending, whereas upregulation of PID reduces PIN3 relocation and bending. The authors introduced phosphomutant variants to the pin3-4 mutant and showed that these variants are not able to complement PIN3 function in root gravitropism. Overall, they presented a phosphorylation based polarity switch model for PIN3 in response to gravitropic stimuli. (Summary by Arif Ashraf) Scientific Reports 10.1038/s41598-018-28188-1