Buti, S. | bioRxiv Science

bioRxiv2022

Mechanodetection of neighbor plants elicits adaptive leaf movements through calcium dynamics

Plants detect their neighbors via various cues, including reflected light and touching of leaf tips, which elicit in upward leaf movement (hyponasty). It is currently unknown how touch is sensed and how the signal is transferred from the leaf tip to the petiole base that drives hyponasty. Here, we show that touch-induced hyponasty involves a signal transduction pathway that is distinct from light-mediated hyponasty. We found that mechanostimulation of the leaf tip upon touching causes cytosolic calcium ([Ca2+]cyt induction in leaf tip trichomes that spreads towards the petiole. Both perturbation of the calcium response and the absence of trichomes inhibit touch-induced hyponasty. Finally, using plant competition assays, we show that touch-induced hyponasty is adaptive in dense stands of Arabidopsis. We thus establish a novel, adaptive mechanism regulating hyponastic leaf movement in response to mechanostimulation by neighbors in dense vegetation.

plant biology↗

bioRxiv2020

A gas-and-brake mechanism of bHLH proteins modulates shade avoidance in Arabidopsis thaliana

Plants detect proximity of competitors through reduction in the ratio between red and far red light triggering the shade avoidance syndrome, which includes accelerated shoot elongation and early flowering. Shade avoidance is regulated through PHYTOCHROME INTERACTING FACTORs (PIFs), a group of bHLH transcription factors. Another (b)HLH protein, KIDARI (KDR), which is non-DNA-binding, was identified in de-etiolation studies and proposed to interact with LONG HYPOCOTYL IN FAR-RED 1 (HFR1), a (b)HLH protein that inhibits shade avoidance. Here we establish novel roles of KDR in regulating shade avoidance and investigate how KDR regulates the shade avoidance network. We show that KDR is a positive regulator of shade avoidance and interacts with several negative growth regulators. We identify novel interactors using a combination of yeast two-hybrid screening and dedicated confirmations with bimolecular fluorescence complementation. We demonstrate that KDR is translocated primarily to the nucleus when coexpressed with these newly discovered interactors. A genetic approach confirmed that several of these novel interactions are indeed functional to shade avoidance in Arabidopsis thaliana, whereas we propose that KDR does not interact with HFR1 to regulate shade avoidance. Based on this, we propose that shade avoidance is regulated by a three-layered gas-and-brake mechanism of bHLH protein interactions, adding an additional layer of complexity to what was previously known. One-sentence summaryKIDARI is a positive regulator of shade avoidance and part of a three-layer network of bHLH transcription factor interactions.

plant biology↗