Using auxin to understand context-dependent hormone response

Duke University, Durham NC

Investigators

Abstract

Title: Using auxin to understand context-dependent hormone response Project Summary Cells constantly integrate a suite of intrinsic and extrinsic information to coordinate their activities. The suite of stimuli perceived by a cell – the context – can drastically alter the response to a subsequent stimulus. The plant hormone auxin provides a fascinating example of this context-dependent response: auxin regulates diverse phenomena from cell expansion to cell fate specification during all aspects of a plant's life. How the same hormone can elicit such diverse responses depending on the context is unknown. Here I propose work to discover genetic factors required for context-depending auxin response. Seedlings of Arabidopsis thaliana respond oppositely to exogenous auxin when grown in the light versus when grown in darkness. I hypothesize that auxin triggers distinct genetic pathways in light and darkness. Using Arabidopsis as a model, I will test this hypothesis first by performing a mutant screen that will isolate novel factors required for context-dependent and context-independent auxin signaling. I will subsequently assay how the DNA-binding landscape of AUXIN RESPONSE FACTOR (ARF) transcriptional effectors compares in light and dark-grown hypocotyls. If ARF binding varies substantially due to context, I will test whether differences in chromatin accessibility underlies this variation. If ARF DNA-binding is similar across contexts, then other factors in complex with the ARFs are likely responsible for modulating auxin response; these will be investigated using TURBO-ID to identify ARF protein complex components. Finally, I will perform time course RNA-seq followed by Gene Regulatory Network (GRN) analysis to assess how the transcriptional response to auxin changes in the light versus in the darkness. Altogether the mutant screen, ARF DNA-binding profiles, and GRNs will elucidate how context affects the response to a stimulus and identify important factors in context-dependent signaling that can be investigated in the future.