ATMRP1 GENE OF ARABIDOPSIS ENCODES A GLUTATHIONE S-CONJUGATE PUMP - ISOLATION AND FUNCTIONAL DEFINITION OF A PLANT ATP-BINDING CASSETTE TRANSPORTER GENE

Because plants produce cytotoxic compounds to which they, themselves, are susceptible and are exposed to exogenous toxins (microbial product s, allelochemicals, and agrochemicals), cell survival is contingent on mechanisms for detoxifying these agents, One detoxification mechanism is the glutathione S-transferase-catalyzed glutathionation of the tox in, or an activated derivative, and transport of the conjugate out of the cytosol. We show here that a transporter responsible for the remov al of glutathione S-conjugates from the cytosol, a specific Mg2+-ATPas e, is encoded by the AtMRP1 gene of Arabidopsis thaliana. The sequence of AtMRP1 and the transport capabilities of membranes prepared from y east cells transformed with plasmid-borne AtMRP1 demonstrate that this gene encodes an ATP-binding cassette transporter competent in the tra nsport of glutathione S-conjugates of xenobiotics and endogenous subst ances, including herbicides and anthocyanins.