Integrating Our Understanding of Proteolysis in Plant Biology

Plant proteolysis mediates the processing and turnover of the cellular proteome. Proteolysis is therefore a key process in plant development and differentiation, proteostasis, (a)biotic stress responses and adaptation, plant metabolism as well as senescence, autophagy and programmed cell death. Plant proteolysis involves proteolytic enzymes (e.g. the proteasome) and their associated regulators as well as sorting mechanisms (e.g. endosomal and autophagic sorting pathways) and substrate-tagging systems (e.g. ubiquitination machinery). Proteolysis is necessary in plant protein maturation, activation and degradation. Proteases recognize their substrates in various ways, including post-translational modifications and conditional degrons that allow the cell to rapidly reshape the proteome and acclimate to adverse conditions. Proteolysis appears to be particularly important to plants given the number of genes devoted to proteolysis in plants like Arabidopsis. For example, plants have the largest number of genes devoted to the ubiquitin-proteasome system of any kingdom (~ 1000 E3 ligases), and over 500 individual proteases of different classes. Plant proteases also have important practical applications, including a major role in agriculture through their impact on yield as well as (a)biotic stress defense, as well as biotechnology. The interest and active research in plant proteolytic processes has grown rapidly over the past decade. These activities and successes have been driven by a combination of novel tools and opportunities, including the advances in genomics, molecular biology, novel tools in cell biology and high-resolution imaging, proteomics and mass spectrometry techniques, in vivo activity labeling and structural biology. Examples of recent developments and breakthroughs include the novel insights in selective and organelle-specific forms of autophagy, discovery of novel N-degrons (e.g. enzymatic cysteine oxidation), the elucidation of proteolytic processing of signaling peptides in plant development and immunity, as well as, N-terminal labeling and enrichment techniques (TAILS, COFRADIC), and novel protein degradation/life-time reporter systems. This new GRC aims to bring together researchers studying all aspects of plant proteolysis and covering a wide range of disciplines, including cell and molecular biology, chemistry and biochemistry, imaging, physics and systems biology, to generate new research avenues and provide solutions to some of society’s challenges.