Poster: Hormones
Abs #
635: PIN1 auxin efflux protein is mislocalized in MDR mutants with enhanced tropisms
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Presenter: |
Murphy, Angus S, murphy@purdue.edu |
Authors | Murphy, Angus S (A) Bandyopadhyay, Anindita (A) Noh, Bosl (B) Blakeslee, Joshua J (A) Peer, Wendy A (A) Spalding, Edgar P (B) | | Affiliations: |
(A): Purdue University
(B): University of Wisconsin, Madison
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Many aspects of stem growth are dependent on the polar movement of auxin, which is thought to be regulated at the cellular level by basal plasma membrane (PM) localization of the PIN1 auxin efflux carrier. Recently, mutations in two multidrug resistance-like genes encoding NPA-binding proteins were shown to inhibit polar auxin transport in the hypocotyls of Arabidopsis seedlings, indicating that MDR-type (p-glycoprotein) ABC transporters function in the PIN1-dependent auxin transport process. However, instead of exhibiting impaired auxin-dependent tropic bending, mdr mutant hypocotyls display enhanced gravitropic and phototropic responses. The impaired auxin transport and enhanced tropism phenotypes can be reconciled by the finding that the pgp mutations disrupt the basal accumulation of the PIN1 protein in hypocotyl cells. Consequently, lateral auxin conductance becomes a larger proportion of the whole with the result of greater growth differentials across the hypocotyl.
Other findings support a role for AtPGP1 and AtMDR1 in regulating auxin transport. 1) Both interact with the PM-anchored FKBP-like protein Twisted Dwarf1 (TWD1), which appears to play a role in p-glycoprotein PM localization and function. twd1 is morphologically similar to mdr1 pgp1 double mutants and exhibits similarly reduced auxin transport profiles. 2) The brachytic2 (br2) dwarf mutant in maize contains a defective PGP (MDR) gene. Vascular tissue formation in br2 seedlings is disrupted, while seedling roots are more highly branched and are less strictly gravitropic. br2 mutants show light-dependent, tissue specific defects in auxin transport analogous to those seen in the Arabidopsis mdr mutants.
