Aman Husbands

  • Feb 11, 2019

Date & Location: February 11, 2019, at 4p; Room 101 Biochemistry Building

Subject: Do ligand-binding transcription factors drive morphological complexity?

Host: Beronda Montgomery

About the Speaker

University: The Ohio State University

Abstract: Biological complexity is accomplished in part by intricate regulation of transcription factor (TF) activity. One particularly powerful mechanism to regulate TF activity is high-affinity ligand binding. This enables organisms to directly integrate signals, and rapidly effect large-scale changes to gene regulatory network outputs. In plants however, the impacts of TF-ligand interactions are virtually unstudied. Here we show that the activity of the CLASS III HOMEODOMAIN-LEUCINE ZIPPER (HD-ZIPIII) family of developmental regulators is directly regulated by their lipid-binding START domain. Our data indicate that HD-ZIPIII proteins adopt a transcriptionally-potent, DNA-binding-competent state upon binding of a phospholipid ligand at their START domain. The START ligand appears to operate as a switch, using an intramolecular mechanism to convert HD-ZIPIII proteins into highly-potent TFs. Intrinsic coupling of transcriptional activity to lipophilic ligand-binding is a hallmark of mammalian nuclear receptors (NRs), and suggests HD-ZIPIII proteins as a new class of plant-specific NRs. Like NRs, HD-ZIPIII proteins are ancient, regulate core biological processes, and their functional diversification parallels the elaboration of complex morphologies. The remarkably similar evolutionary properties of HD-ZIPIII and animal NRs may reflect a specific and important role for ligand-binding TFs in the acquisition of developmental complexity.