NSF Undergraduate Researcher Skidmore College Amsterdam, New York
Body of Abstract: Approximately 600 million years ago, an ancestor of Charophycean green alga successfully invaded terrestrial habitat and ultimately yielded modern day land plants. Through genomic analyses, Penium margaritaceum is suggested to be the closest living descendant to this divergence between algae and terrestrial plants, in turn opening pathways for a new model organism of great evolutionary significance. One of the more distinct features of many of these algae is the large and complex extracellular matrix (ECM) that they secrete. This includes cell walls with notable biochemical similarity to those found in many land plants and complex and often prolific amounts of a gel-like extracellular polymeric substance (EPS) secreted beyond the wall. The secretory machinery that processes the ECM includes a highly ordered set of stationary Golgi bodies, an assortment of secretory vesicles, and a cytoskeletal network that incudes microtubules and actin. In this study, we performed an experimental and structural analysis of the secretion apparatus of the unicellular zygnematophyte, Penium margaritaceum. Specifically, we screened a large library of chemical agents and subcellular inhibitors that target specific components of the secretion process. Cells were observed using a variety of microscopy techniques. Results suggest structural changes to the Golgi apparatus when treated with Golgicide, BFA, and Endosidin 5. Changes to exocytosis of ECM was characterized by cell wall alteration and changes to EPS secretion. Pectate lyase was shown to have great impact on cell wall integrity. EPS inhibition was categorized into 4 groups: no EPS production, capsuling, tufting, and shortened trails. SMIFH2 produced tufting of EPS around the cells. Our data reveals significant structural and functional disruptions to the secretory apparatus through targeted inhibitors. These disruptions can be used to further elucidate the evolutionary and genetic processes of land plants and secretion studies.