Phosphoproteomic Analysis Of A Ser/Thr Protein Kinase PID Mediated Signaling In Arabidopsis

Polar transport of auxin is important for plant growth and development.The directional auxin flow depends on the polar subcellular localization of PIN auxin efflux regulators in plant.Overexpression of the PINOID protein kinase induces a basal-topical shift in PIN localization,resulting in the loss of auxin gradients and strong defects in embryo and seedling roots.In this study,the phosphorylated peptides in seedlings of 35S::PID and wide type Arabidopsis were analyzed using solid metal affinity chromatography and dimethyl tag-based quantification mass spectrometry approaches.In 35S::PID seedlings,383 increased and 607 decreased proteins,as well as 360 induced and 187 reduced phosphorylated proteins were identified.The alterations of protein expression patterns and phosphorylated levels revealed that overexpressed PINOID protein kinase led to the enhanced phosphorylation of PIN,changes of PIN polarity,and altered auxin gradients.This resulted in the changes of phytohormone-related signaling networks,such as BR signaling pathway,ABA signaling pathway and calcium signaling pathway.The proteomic and phosphoproteomic result also revealed that sugar/starch metabolism,glycolysis and tricarboxylic acid cycle were activated,as well as cell wall polysaccharide metabolism were activated,which provided energy for lateral root growth.These provide important evidence for understanding the function of PID regulation in auxin polar transport.