Understanding the Shade Tolerance Responses Through Hints From Phytochrome A-Mediated Negative Feedback Regulation in Shade Avoiding Plants.

Huiying Xu,Yi Tao,Peirui Chen

doi:10.3389/fpls.2021.813092

Abstract

Based on how plants respond to shade, we typically classify them into two groups: shade avoiding and shade tolerance plants. Under vegetative shade, the shade avoiding species induce a series of shade avoidance responses (SARs) to outgrow their competitors, while the shade tolerance species induce shade tolerance responses (STRs) to increase their survival rates under dense canopy. The molecular mechanism underlying the SARs has been extensively studied using the shade avoiding model plant Arabidopsis thaliana, while little is known about STRs. In Aarabidopsis, there is a PHYA-mediated negative feedback regulation that suppresses exaggerated SARs. Recent studies revealed that in shade tolerance Cardamine hirsuta plants, a hyperactive PHYA was responsible for suppressing shade-induced elongation growth. We propose that similar signaling components may be used by shade avoiding and shade tolerance plants, and different phenotypic outputs may result from differential regulation or altered dynamic properties of these signaling components. In this review, we summarized the role of PHYA and its downstream components in shade responses, which may provide insights into understanding how both types of plants respond to shade.

Highlights

Plants grown in complex and dynamic light environments are constantly in fierce competition with their surrounding neighbors for limited light sources
Species typically found in forest understories exhibit shade tolerance responses (STRs), which allows them being adapted to shade environment
FHY3 (FARRED ELONGATED HYPOCOTYL3) and FAR1 (FAR-REDIMPAIRED RESPONSE1) are two homologous transcription factors that act downstream of PHYTOCHROME A (PHYA) in FR light signaling (Wang and Deng, 2002; Lin et al, 2007). fhy3far1 mutant displayed exaggerated hypocotyl elongation under shade, which was similar to phyA (Liu et al, 2019)

Summary

INTRODUCTION

Plants grown in complex and dynamic light environments are constantly in fierce competition with their surrounding neighbors for limited light sources. The upper leaves preferentially absorb blue (B, λ = 400–500 nm) and red (R, λ = 600–700 nm) light for photosynthesis while reflecting most of the far-red (FR) (λ = 700– 800 nm) light (Vandenbussche et al, 2005; Franklin, 2008). PHYA functions to tune down the SARs under excessive or prolonged shade conditions, which may allow the shade avoiding species to become tolerant to shade (Song et al, 2020). We summarize results from recent studies on the role of PHYA in regulating low R:FR induced SARs, which may provide hints for understanding the potential mechanism of the STRs

THE SHADE AVOIDANCE RESPONSES

THE SHADE TOLERANCE RESPONSES

REGULATION OF PHYTOCHROME INTERACTING FACTORS BY PHYTOCHROME A

PHYTOHORMONES AND THE PHYTOCHROME A SIGNALING PATHWAYS

CONCLUSION