Collaborative Research:RUI: Invasion of land: Using model charophyte Penium margaritaceum to elucidate subcellular responses to stress that were key in the evolution of land plants

Cornell University, Ithaca NY

Investigators

Abstract

The colonization of land by green algae 450 to 500 million years ago and their evolution into land plants represent important events in the natural history of the planet. These terrestrial (land) plants have caused major changes to the Earth's biochemistry and biosphere. Land plants evolved from green algae called charophytes, a small but diverse group of freshwater and terrestrial organisms. Central to the success of the charophyte colonization of land was the extracellular matrix (ECM) that surrounds their cells. This ECM is made up of a wall that covers the outside of the cell and the gel-like substances that are secreted from these organisms. This project will provide a comprehensive understanding of the formation and function of the ECM of the charophyte being tested, Penium. This organism will be grown under various environmental conditions, including water stress and extreme dryness. The ECM and its related biosynthetic processes will be studied using cutting edge technologies that were previously funded by the National Science Foundation. This research will provide insight into the mechanisms that were important to initiate survival on land by ancient charophytes, as well as mechanisms that are still used by many land plants today. This information will be used to devise models of how plants adapt to life on land and how they tolerate non-biological stresses such as drought. This project will also provide opportunities for post-doctoral training and summer undergraduate research, initiate external summer programs for local high school students, and serve as a basis for future course development. The goal of this project is to provide a comprehensive understanding of the extracellular matrix (ECM) and its biosynthesis dynamics in the model charophyte, Penium. It will examine the changes that occur in ECM processing when cells are placed under desiccation stress. The ECM and its biosynthetic machinery will be studied using molecular, biochemical, and high resolution microscopy technologies previously funded by the National Science Foundation. This will provide insight into mechanisms that were important to survival on land by ancient charophytes and continue to be used by many land plants, including those exposed to drought. Specific areas to be studied include: (A) polar cell growth in Penium, with an emphasis on pectin and cellulose production during wall expansion; (B) the secretion of ECM components involving two distinct pathways, the cell wall polysaccharides delivered to specific expansion zones along with extracellular polymeric substances extracellular (EPS) targeted to transitory secretion sites; (C) changes in cell wall architecture; and (D) EPS targeted production and delivery that are critical for tolerating abiotic stresses. The results of this project will be of significance to the fields of plant evolutionary biology, cell biology, molecular biology, and developmental biology. This project will also provide significant opportunities for outreach and student training.