RUI: Functional Characterization of a Geminivirus AC4 N-myristoylated Protein

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Geminiviruses infect a broad range of economically important crop species all over the world and are increasingly being shown to occur in mixed infections, resulting in synergistic interactions, characterized by severe symptoms and huge yield losses. Partly because of mixed infections, these viruses undergo recombination, presumably during replication, resulting in more virulent strains than their pedigree. One of the crops severely affected by these viruses is cassava (Manihot esculenta Crantz), a root crop that serves as a staple food to more than 500 million people worldwide. This new cassava virus, named East African cassava mosaic Cameroon virus (EACMCV) was isolated from cassava fields in Cameroon. We have shown that the EACMCV encoded AC4 protein is a symptom determinant and suppresses virus induced gene silencing (VIGS), an antivirus mechanism exhibited by eukaryotic plants. These studies also showed that AC4 targets the plasma and cytosolic membranes. Mutantional analyses showed that these properties depend on the AC4 encoded N-myristoylation motif, a membrane-binding motif, suggesting, that to function, AC4 must be within a membrane locale. These unique features and its small size (10 kDa) make AC4 a potentially good probe to dissect and elucidate physiological and biochemical events occurring within the plant cell membrane following virus infection. The specific aims of this project are to: 1) Determine the role of AC4 protein in EACMCV pathogenesis, 2) Investigate the interaction between AC4 and the proteins that have been identified in a yeast two-hybrid screen, and 3) Functionally characterize the AC4-interacting proteins.Since the plasma membrane plays an important role in trafficking in and out of the cell, AC4 likely plays an important role in virus entry and/or exit. This project will identify and characterize membrane proteins that interact with AC4 since such proteins might play a role in geminivirus infection, which would be crucial as new approaches are sought to control these viruses. An important component of this project is the training of undergraduate students, mostly from underrepresented minority groups, in molecular biology and biotechnology. This training will make these students competitive in the fast growing biotechnology job market upon graduation.