Biological and Agricultural Engineering

March 3 – BAE Departmental Seminar: Georgia Drakakaki Department of Plant Science

Tuesday, March 3, 2015
1:10 PM

2045 Bainer Hall




Dissecting polysaccharide deposition during cytokinesis and plant morphogenesis




Georgia Drakakaki

Department of Plant Science,

UC Davis





Plant cell walls are composed primarily of structural carbohydrates that can be broken down into sugars, providing energy directly as food/feed, or indirectly as biofuels. A greater understanding of their synthesis and assembly can lead to the development of more nutritious food/feed and more accessible biofuels. While cell wall structure and biosynthesis have been extensively studied, little is known about the transport of polysaccharides into the developing cell wall. The endomembrane system has been implicated in this process, however our mechanistic understanding of the highly regulated membrane and cargo transport mechanisms in relation to polysaccharide deposition is yet very limited.

Our research is focusing on how plant cells direct different polysaccharides, cell-wall biosynthetic enzymes and other components into the developing cell wall. We are employing a highly multidisciplinary approach in our studies that comprises chemical genomics, proteomics and genetics. Chemical genomics circumvents lethality challenges present in conventional genomic approaches and allows us to pursue the study of pathways that were hitherto impossible.

We have identified novel pharmacological inhibitors, which specifically target cell wall deposition during cell division and/or during cell elongation. Among them is, Cestrin a novel inhibitor of cellulose synthase localization. It reduces the cellulose content in plants, and interferes with the interplay of cellulose synthases with microtubules. Its behavior affords the identification of new players involved in the organization of cellulose synthase complexes at the plasma membrane. A further pharmacological inhibitor that we have identified is Endosidin 7. It targets specifically and in a time dependent manner callose synthase activity during late cytokinesis and arrests cell plate maturation. Our data detail the essential role of callose during the late stages of cell plate maturation and establish a model that describes the temporal relationship between vesicles and regulatory proteins at the cell plate assembly matrix during polysaccharide deposition.

In a complementary extension of our studies we used a proteomic approach, to identify components of the endomembrane system that are present in the trans-Golgi Network, a site of polysaccharide trafficking and recycling of endosomal components. Vesicle isolation affords the most direct dissection of the role that vesicles play in stress response and growth. Identification of the SYP61 vesicle proteome revealed the presence of proteins involved in cell wall biosynthesis, modification and in adaptive stress responses. Interestingly cellulose synthases were identified in the SYP61 vesicle proteome, indicating that SYP61 vesicles are involved in the trafficking of the CESA complexes. Based on our cumulative data, we propose that SYP61 mediates trafficking of cell wall and stress response components.

2045 Bainer Hall University of California Davis

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