Poster: Membrane Transport

Abs # 1231: A multidrug-resistance associated protein involved in anthocyanin transport in Zea mays.

Presenter:	Goodman, Christopher D, cdgood@stanford.edu
Authors	Goodman, Christopher D (A)   Walbot, Virginia  (A)
Affiliations:	(A): Stanford University

Anthocyanin biosynthesis is one of the most well-studied enzymatic pathways in biology but little is known about the molecular mechanisms of its final stage; the transport of the anthocyanin pigment into the vacuole. We have identified a multidrug-resistance associated protein, ZmMRP1, involved in this transport process. ZmMRP1 expression is controlled by the regulators of anthocyanin biosynthesis and mirrors the expression of other anthocyanin structural genes. Localization of ZmMRP1 in vivo shows its presence in the tonoplast, the site at which anthocyanin transport occurs. Mutants generated using antisense constructs have a distinct pigmentation phenotype in the adult plant that results from a significant reduction in anthocyanin levels but no alteration in the ratio of anthocyanin species produced. Surprisingly, no aleurone phenotype was observed in mutant plants. This appears to be reflect the presence of second, highly homologous gene - ZmMRP2 - that is also co-regulated with the anthocyanin pathway but is expressed exclusively in the aleurone. This is the first description of a plant MRP with a known endogenous substrate and, as such, provides a new model system for examining the biological and biochemical mechanisms involved in the MRP-mediated transport of plant secondary metabolites.