title: A per-ARNT-sim-like sensor domain uniquely regulates the activity of the homeodomain leucine zipper transcription factor REVOLUTA in Arabidopsis.
abstract: Class III homeodomain leucine zipper (HD-ZIP III) transcription factors regulate critical developmental programs in plants; these include leaf polarity, polarity along the shoot-root axis, and stem cell specification and proliferation. One of the defining features of HD-ZIP III proteins is the presence of a Per-ARNT-Sim-like (PAS-like) MEKHLA domain at the C terminus. PAS-like domains are known to respond to a variety of chemical and physical stimuli. Here, we provide evidence that the MEKHLA domain acts as a negative regulator of Arabidopsis thaliana HD-ZIP III REVOLUTA activity. Based on experiments in yeast and plants, we propose a model in which the MEKHLA domain inhibits dimerization through a sequence-independent steric masking mechanism. This inhibition is relieved in response to a cellular signal that requires the C terminus of the MEKHLA domain for its perception. Overexpression experiments suggest that this signal is unequally distributed and/or sensed in the plant. Our data show that the function of the REVOLUTA MEKHLA domain differs among other HD-ZIP III family members; this difference may explain the genetic differences that have been observed among family members. This finding, combined with our phylogenetic analysis, suggests that REVOLUTA is the latest type of HD-ZIP III protein to have evolved in land plants.
authors.affiliation: Department of Plant Biology, Carnegie Institution, Stanford, California 94305, USA.
authors.forename: Enrico
authors.initials: E
authors.lastname: Magnani
authors.forename: M Kathryn
authors.initials: MK
authors.lastname: Barton
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D019295:Computational Biology; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D016350:Leucine Zippers; D008969:Molecular Sequence Data; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D054730:Protein Interaction Domains and Motifs; D055503:Protein Multimerization; D016415:Sequence Alignment
chemical_list: D029681:Arabidopsis Proteins; D018398:Homeodomain Proteins; C402597:IFL1 protein, Arabidopsis