Multidrug Resistance-Like Genes and Auxin Transport

University Of Wisconsin-Madison, Madison WI

Investigators

Abstract

This project is designed to determine the functions of AtMDR1 and other proteins encoded by a group of ABC transporter genes in Arabidopsis that are homologous to multi-drug resistance (MDR) proteins of animals. The animal MDR proteins are most often studied for their roles in the resistance of cancer tumors to chemotherapeutic drugs. This research will investigate the roles these proteins play in plants. Genetic, biochemical, and physiological evidence indicates that at least two of the Arabidopsis MDR proteins participate in the transport of the plant hormone auxin, and thus are important to plant growth and development. The auxin-transport inhibitor NPA binds tightly to AtMDR1 and AtPGP1 proteins. Knockout mutants lacking these proteins have severe defects in polar auxin transport. The phenotypes of the knockout mutants are consistent with abnormal auxin distribution being the cause. The research activities that produced the substantial background information on these two genes will be reiterated to reach some never-before studied genes within the MDR-like subcluster. In addition, biochemical studies will test hypotheses about the mechanism of AtMDR1 function. For example, is it an auxin transporter or a regulator of an auxin transporter? The experimental plan includes characterizing knockout phenotypes, determining the effects of the knockout mutations on auxin distribution, and biochemical studies of the AtMDR1 gene after expression in a heterologous system. The two PIs responsible for the project have complementary areas of expertise and will provide interdisciplinary training for postdoctoral research associates and graduate students. The dissection of these interesting genes genetically, biochemically, and physiologically is expected to provide new insight into the hormonal control of plant growth and development.