Titapiwatanakun, Boosaree , Bandhyopadhyay, Anindita , Blakeslee, Josh , Peer, Wendy , Murphy, Angus .
Functional and interacting domains of AtPGP4 that confer directionality of auxin transport.
P-glycoprotein (PGP) and PIN-FORMED (PIN) proteins constitute key components of polar auxin transport mechanisms in plants. PINs and PGP1/19 function as auxin efflux transporters. However, when PINs and PGPs are expressed independently in heterologous systems, they exhibit reduced substrate specificity compared to what is seen in planta. Co-immunoprecipitation assays demonstrated PIN-PGP interactions,¬†and yeast two-hybrid assays showed that the C-terminal region of PGP19, but not PGP1 interacts directly with PIN1 and PIN2. Further, co-expression of PGPs and PINs in heterologous systems increases substrate/inhibitor specificities and alters transport directionality. Gene expression and immunolocalization studies showed that the subcellular localization of PGP19 overlaps with that of PIN1 in the shoot apex and with PIN1 and PIN2 in the root, suggesting tissue-specific interactions between PGPs and PINs. Phenotypes of pin and pgp mutants suggest discrete functional roles in auxin transport, but pin pgp mutants exhibit phenotypes that are both additive and synergistic. Mutational or chemical interference of interactions between the PGP19 C-terminus and other transport complex proteins also alters transport velocity and specificity. Similar interactions can be found with PGP4, as the directionality of PGP4-mediated auxin transport can be reversed by co-expression with PIN1. As PGP4 and PGP19 are expressed in distinct tissues where different sets of interacting proteins may modify their auxin transport properties, we hypothesize that the interactions between the N-terminus of PGP4 and the C-terminus of PGP19 and PGP4 with other cellular constituent play a role in regulating directionality of auxin transport.
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1 - Purdue University, Department of Horticulture and Landscape Architecture, 625 Agriculture Mall Drive, West Lafayette, IN, 47907, USA
2 - Purdue University, Department of Horticulture and Landscape Architecture
3 - Brown University, Department of Biology
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM