Mechanistic and genetic regulation of plant responses to vegetation proximity: the roles of DRACULA2 and HFR1

Abstract

Light provides essential energy for plant photosynthesis and information about the surrounding environment. Light challenging conditions, such as vegetation proximity and shade, require fast response and a fine-tuned signalling network to properly adapt plant development. Several transcriptional regulators are at the core of plant responses to vegetation proximity, including the positively-acting PHYTOCHROME INTERACTING FACTORs (PIFs) and the antagonistic HFR1. Nonetheless, knowledge about the regulation of shade responses improves continuously. DRACULA2 (DRA2) is a newly identified Arabidopsis thaliana shade avoidance regulator, part of the nuclear pore complex (NPC), which affects several aspects of plant development (e.g., shade-induced hypocotyl elongation) through transport-dependent and -independent activities. Besides its pleiotropic phenotype shared with other nucleoporin (NUP)-deficient mutants, DRA2 is specifically involved in the regulation of shade-induced gene expression. We found that DRA2 is a dynamic NUP, i.e., not exclusively NPC located, which could allow it to act independently of the NPC. Moreover, transport-dependent functions of the NPC might be part of a broader mechanism of shade regulation. While shade avoidance is better studied, we are beginning to understand the regulation of an alternative plant strategy to vegetation proximity, tolerance to shade, by using Cardamine hirsuta, a close relative of A. thaliana. We demonstrated that C. hirsuta HFR1 inhibits hypocotyl elongation in shade by constraining the expression profile of shade induced genes. HFR1 accumulates in shade and directly interacts with various PIFs, such as the major shade avoidance promoting PIF7 in A. thaliana. We show that a higher stability in shade coupled with higher expression levels can lead to a higher biological activity of HFR1 in C. hirsuta resulting in the shade tolerance habit of C. hirsuta.

Date of Award	17 Jul 2018
Original language	English
Supervisor	Jaime F. Martínez-García (Director) & Charlotte Poschenrieder (Tutor)