Pho-view of Auxin: Reversible Protein Phosphorylation in Auxin Biosynthesis, Transport and Signalling.

Abstract The phytohormone auxin plays a central role in shaping plant growth and development. With decades of genetic and biochemical studies, numerous core molecular components and their networks, underlying auxin biosynthesis, transport and signalling, have been identified. Notably, protein phosphorylation, catalysed by kinases and oppositely hydrolysed by phosphatases, has been emerging to be a crucial type of post-translational modification, regulating physiological and developmental auxin output at all levels. In this review, we comprehensively discuss earlier and recent advances in our understanding of genetics, biochemistry and cell biology of the kinases and phosphatases participating in auxin action. We provide insights into mechanisms, by which reversible protein phosphorylation defines developmental auxin responses, discuss the current challenges, and also propose our perspectives for further directions to integrate control of protein phosphorylation into the molecular auxin network.