Molecular Mechanisms of Plant UFMylation in Modulating Autophagy Under Heat Stress

Plants as sessile organisms continuously defend themselves against environmental stresses. At the protein level, both translational regulation and post-translational modifications (PTMs) tightly control the synthesis or degradation of stress-responsive proteins to response to environmental stimulus. At the organelle level, de novo biogenesis of healthy novel organelles and the degradation of stressed old compartments constantly meet the increased need for synthesizing or transporting stress-responsive proteins and waste removal. Autophagy turns over cellular materials upon nutrient deprivation or in adverse environments. Dysfunction of autophagy leads to survival and developmental defects under stresses. Recent studies have uncovered the role of a ubiquitination-like PTM, UFMylation, involving in the crosstalk of endoplasmic reticulum (ER) stress responses and autophagy in both animals and plants. Key scientific questions in plants include identifying the substrates of UFMylation that respond to specific environmental signals, as well as elucidating the receptors or regulatory mechanisms underlying the role of UFMylation in coordinating autophagy and organelle homeostasis. Our recent discoveries of UFMylation in modulating plant ER-phagy triggered by salt stress-induced ER stress have inspired us to further investigate whether UFMylation also modulates other stress-responsive trafficking pathways and their molecular mechanisms. In our preliminary studies, we observed a heat stress hypersensitive phenotype in mutants of the UFL1, key E3 ligase component in the UFMylation cascade. We therefore aim to further perform pull-down mass spectrometry (MS) screening to investigate underlying molecular mechanisms of how plant UFMylation might modulate autophagy under heat stress.