MAP kinase regulation of PIN-FORMED auxin transporters

• Applicant: Professor Dr. Claus Schwechheimer
• Subject Area: Plant Cell and Developmental Biology
• Term: from 2020 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 446615548

Auxin is a mobile plant hormone that is directionally transported from cell-to-cell through the activity of polarly distributed PIN auxin efflux transporters. Understanding auxin transport activity and directional transport is of great importance for the understanding of fundamental processes in plant development. In recent years, we and others have elucidated the role of PIN phosphorylation at conserved serine (S) residues for the regulation of PIN activity, plasma membrane distribution and polarity. Strikingly, three PIN serine residues required for PIN activation and polarity control, S1 – S3, reside in close proximity to hypothesized MAP kinase-targeted threonine phosphosites, T1 – T3, in the highly conserved T1PRXS1 – T3PRXS3 motifs. The role of T1 – T3 phosphosite phosphorylation, as well as that of a co-regulated S337 MAP kinase target site, for PIN function has not been elucidated as yet. Here, I propose to use immunostaining with phosphosite specific antibodies and quantitative phosphoproteomics to study the distribution and abundance of T phosphosite phosphorylation, alone and in conjunction with S phosphosite phosphorylation. Further, I propose to study the abundance of these phosphorylations in MAP signalling mutants to identify in planta MAP signalling cascades required for T phosphorylation. Finally, I propose to examine the role of T phosphosite phosphorylation for PIN activation, polarity control and other cell biological functions using a combination of genetics, cell biology and physiology, in isolation and together with S1 – S3 phosphorylation.

• DFG Programme: Research Grants