N-degron pathways in plants impact on stress resilience

N-degron pathways in plants impact on stress resilience

3^rd Annual Congress on Plant Biology & Agricultural Sciences
April 04, 2022 | Webinar

Andreas Bachmair

University of Vienna, Austria

Abstract:

Many processes of adaptation to adverse conditions require abundance changes in the proteome. Changes at the amino terminus of proteins impact on protein turnover, because protein half-lives critically depend on the structure of the amino terminus. So-called N-degrons are recognized by ubiquitin ligases, to channel them into proteasomal turnover. Alternatively, autophagy receptors can encompass binding domains to feed vacuolar/ lysosomal degradation. Plants employ several pathways to degrade proteins with bulky first residues. Whereas proteins starting with basic amino acids Arg, Lys and His are recognized by PRT6, a ubiquitin ligase with similarity to mammalian UBR1 and 2, proteins with hydrophobic first residues have different turnover paths. One plant-specific ubiquitin ligase (PRT1) recognizes aromatic first residues. Based on mutant screens and inhibitor studies, we found that degradation of proteins with aliphatic hydrophobic first residues such as Leu occurs both via the vacuole, and by the proteasome. We present data on genes involved in these two degradation pathways. In addition, heterologous expression of plant ubiquitin ligases allows to study these in a non-redundant background. We use yeast as a host for PRT6 and other UBR domain proteins of Arabidopsis to study their ability to act as N-recognins and to learn about their substrate preferences. In this assay, PRT6 requires Arabidopsis UBC2 as cognate E2 for activity. The existence of multiple degradation routes offers flexibility to a plant cell. While the PRT6-mediated pathway is central for response to flooding, and PRT1 has a role in biotic stress responses, the biological functions of the other pathways remain to be determined.

Biography:

A.B. is a professor at the University of Vienna. Andreas Bachmair finished his PhD at the University of Vienna and started his career as a Postdoctoral Fellow at the MIT and the Max Planck Institute for Plant Breeding research in Cologne, Germany. After holding assistant and associate professorships at the Institute of Botany of the University of Vienna he became group leader at the MPI, a position he held until 2008. He then returned to Vienna as group leader and associate professor at the Max F. Perutz Laboratories.

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