Role of ATG8 specialization in plant selective autophagy

Phenotypic plasticity is the ability of an organism to adapt to changing environmental conditions. It involves modulating cellular programs, such as metabolism and endomembrane transport, in response to specific environmental cues. These subcellular adjustments underlie variations in plant growth and architecture across different ecological niches. It is a key adaptive mechanism that enables plants to cope with environmental unpredictability. Therefore, understanding the molecular basis of the homeostatic processes that underlie phenotypic plasticity is critical for developing crop varieties that can cope with irregular environmental conditions. Autophagy is an essential quality control mechanism that ensures the timely removal of unwanted or excess macromolecules that could otherwise harm the cell. Autophagy is a very potent recycling/membrane transport process. In contrast to the ubiquitin/proteasome system, where cargo proteins are tagged, unfolded, and degraded one by one at the proteasome, autophagic cargoes are rapidly quarantined from the rest of the cytoplasm. Hence, autophagy facilitates dynamic cell-state switches that are critical for remodeling the cell to adapt to the current environment. Initial studies suggested autophagy is a starvation-induced bulk degradation process. However, it is now well established that autophagy is highly selective. So far, most of the studies on autophagy in plants have focused on the functional characterization of the core ATG machinery. The degree to which selective autophagy contributes to environmental adaptation is poorly understood in plants. The ubiquitin like protein ATG8 is a key player in selective autophagy. The ATG8 gene family is expanded in plants. Functional specialization of the ATG8 gene family, which could contribute to selective autophagy, is currently being overlooked in the plant autophagy field. The central hypothesis of the proposed research is that unique structural elements underpin ATG8 specificity, and ATG8 specialization contributes to selective autophagy. At the completion of this project, we will have generated a thorough understanding of the biophysical properties of ATG8 specialization and expanded the selective autophagy toolbox in plants. This multidisciplinary project will pave the way for future studies that will further dissect selective autophagy in plants and reveal its contribution to phenotypic plasticity in plants.

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