Integrity of the Plant Golgi

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Intellectual merit. It is well established that cells of plants, fungi, and animals contain organelles that carry out vital functions for the life of a cell. What is yet to be learned is how the identity of organelles is established and maintained. In this project, the plant Golgi apparatus will be used as a model to address this fundamental question. In plants, the Golgi apparatus is composed of highly mobile stacks of membranes that are dispersed on tubules of another organelle, the endoplasmic reticulum (ER). The plant Golgi receives proteins and membranes from proximal and distal locations; it is involved in their modification and sorting to their final destinations and in synthesizing the cell wall that encapsulates plant cells. The flow of membrane proteins through the Golgi as well as the dynamic exchange of peripherally associated proteins require continuous remodeling of this organelle. Yet, the stacks withstand dispersion during the intense traffic of proteins to and from the Golgi. This raises the fundamental biological question: How does the Golgi retain its integrity (i.e. architecture and composition)? The integrity of the Golgi depends on the organelle's ability to dynamically maintain its steady-state architecture and membrane distribution during protein traffic. Using a screen specifically developed for the plant Golgi in the Brandizzi laboratory, a unique set of mutants was identified in which an established Golgi marker is partially mis-targeted to other organelles. This screen is exciting because it sets the foundation for identifying key players of the machinery that controls plant Golgi integrity. In this project, characterization of the Golgi mutants will be carried out to identify the protein(s) responsible for the maintenance of the architecture and membrane steady-state distribution at the plant Golgi. This work will lead to answers to fundamental questions regarding organelle biogenesis and important differences in Golgi organization and function across eukaryotic biological systems. Broader impacts. Plants are the primary energy source of all biospheric development: all animals survive on plants, both directly and indirectly. The secretory pathway of plants plays a fundamental role in the conversion of fixed carbon into energy-rich materials such as proteins, lipids, and complex sugars. These plant-derived products are important not only for nutrition, but they have the potential to be used as renewable fuels, lubricants, textiles, and building materials of all kinds. The plant Golgi is a key organelle in cell wall biosynthesis and storage protein deposition. Because unique variations exist among systems as a result of evolutionary adaptation, it is important to study the plant Golgi if humanity is to tap into the full potential of plants as primary providers of bio-molecules on earth. This project will also enable the Brandizzi lab to continue their engagement in teaching and outreach activities to communicate to students and teachers the scientific discoveries in plant science and their impact on our society.