TY - JOUR ID - 1279 TI - Complex regulation of the TIR/AFB family of auxin receptors JO - Proc Natl Acad Sci USA PY - 2009 SP - 22540-22545 AU - Parry, G. AU - Calderón Villalobos, L.I. AU - Prigge, M. AU - Peret, B. AU - Dharmasiri, S. AU - Itoh, H. AU - Lechner, E. AU - Gray, W.M. AU - Bennett, M. AU - Estelle, M. VL - 106(52) UR - http://www.pnas.org/content/106/52/22528.full DO - 10.1073/pnas.0911967106 AB - Auxin regulates most aspects of plant growth and development. The hormone is perceived by the TIR1/AFB family of F-box proteins acting in concert with the Aux/IAA transcriptional repressors. Arabidopsis plants that lack members of the TIR1/AFB family are auxin resistant and display a variety of growth defects. However, little is known about the functional differences between individual members of the family. Phylogenetic studies reveal that the TIR1/AFB proteins are conserved across land plant lineages and fall into four clades. Three of these subgroups emerged before separation of angiosperms and gymnosperms whereas the last emerged before the monocot-eudicot split. This evolutionary history suggests that the members of each clade have distinct functions. To explore this possibility in Arabidopsis, we have analyzed a range of mutant genotypes, generated promoter swap transgenic lines, and performed in vitro binding assays between individual TIR1/AFB and Aux/IAA proteins. Our results indicate that the TIR1/AFB proteins have distinct biochemical activities and that TIR1 and AFB2 are the dominant auxin receptors in the seedling root. Further, we demonstrate that TIR1, AFB2, and AFB3, but not AFB1 exhibit significant posttranscriptional regulation. The microRNA miR393 is expressed in a pattern complementary to that of the auxin receptors and appears to regulate TIR1/AFB expression. However our data suggest that this regulation is complex. Our results suggest that differences between members of the auxin receptor family may contribute to the complexity of auxin response. A2 - C1 - Molecular Signal Processing ER - TY - JOUR ID - 854 TI - Auxin signaling JO - Curr Opin Plant Biol PY - 2006 SP - 448-453 AU - Quint, M. AU - Gray, W.M. VL - 9 UR - DO - 10.1016/j.pbi.2006.07.006 AB - Auxin regulates a host of plant developmental and physiological processes, including embryogenesis, vascular differentiation, organogenesis, tropic growth, and root and shoot architecture. Genetic and biochemical studies carried out over the past decade have revealed that much of this regulation involves the SCFTIR1/AFB-mediated proteolysis of the Aux/IAA family of transcriptional regulators. With the recent finding that the TRANSPORT INHIBITOR RESPONSE1 (TIR1)/AUXIN SIGNALING F-BOX (AFB) proteins also function as auxin receptors, a potentially complete, and surprisingly simple, signaling pathway from perception to transcriptional response is now before us. However, understanding how this seemingly simple pathway controls the myriad of specific auxin responses remains a daunting challenge, and compelling evidence exists for SCFTIR1/AFB-independent auxin signaling pathways. A2 - C1 - Molecular Signal Processing ER -