Long‐term abscisic acid promotes golden2‐like1 degradation through constitutive photomorphogenic 1 in a light intensity‐dependent manner to suppress chloroplast development

Abstract

Abiotic stress, a serious threat to plants, occurs for extended periods in nature.Abscisic acid (ABA) plays a critical role in abiotic stress responses in plants. Therefore, stress responses mediated by ABA have been studied extensively, especially in shortterm responses. However, long-term stress responses mediated by ABA remain largely unknown. To elucidate the mechanism by which plants respond to prolonged abiotic stress, we used long-term ABA treatment that activates the signalling against abiotic stress such as dehydration and investigated mechanisms underlying the responses. Long-term ABA treatment activates constitutive photomorphogenic 1 (COP1). Active COP1 mediates the ubiquitination of golden2-like1 (GLK1) for degradation, contributing to lowering expression of photosynthesis-associated genes such as glutamyl-tRNA reductase (HEMA1) and protochlorophyllide oxidoreductase A (PORA), resulting in the suppression of chloroplast development. Moreover, COP1 activation and GLK1 degradation upon long-term ABA treatment depend on light intensity. Additionally, plants with COP1 mutation or exposed to higher light intensity were more sensitive to salt stress. Collectively, our results demonstrate that longterm treatment of ABA leads to activation of COP1 in a light intensity-dependent manner for GLK1 degradation to suppress chloroplast development, which we propose to constitute a mechanism of balancing normal growth and stress responses upon the long-term abiotic stress.

E3 ligase BRUTUS Is a Negative Regulator for the Cellular Energy Level and the Expression of Energy Metabolism-Related Genes Encoded by Two Organellar Genomes in Leaf Tissues

“…Total protein extracts were prepared as described previously with some modifications ( Lee et al, 2021 ). Plant leaf tissues were ground in liquid nitrogen and homogenized using extraction buffer (50 mM Tris–HCl, pH 7.5, 150 mM NaCl, 1 mM EDTA, 0.1% Triton X-100, EDTA-free protease inhibitor cocktail [Roche, Switzerland]).…”

The Role of E3 Ubiquitin Ligases in Chloroplast Function

“…Recently, several studies have illuminated an intriguing connection linking hormone, light, and retrograde signaling pathways to the fundamental role of COP1-mediated degradation in chloroplast biogenesis [ 44 , 53 , 67 ]. ABA is a plant hormone participating in stress signaling and functions antagonistic to light signaling to control developmental processes such as seed germination and stomatal movement [ 68 , 69 , 70 ].…”

Basic Protein Modules Combining Abscisic Acid and Light Signaling in Arabidopsis

“…Endogenous basal ABA does not directly suppress photosynthesis and inhibits a stress-escape response (avoidance of stress through reproduction, a response that is unfavorable for an individual plant, but necessary to preserve the species) under normal conditions, allowing plants to accumulate biomass and increase yield ( Negin et al, 2019 ). However, long-term ABA treatment causes COP1 activation in a light intensity-dependent manner to suppress chloroplast development and balance growth and stress responses ( Lee et al, 2021 ). PhyB stimulates the ABA biosynthesis in the shoots, and mobile shoot-to-root ABA signaling links phyB-mediated light perception with root reactive oxygen species (ROS) homeostasis for optimal plant propagation ( Ha et al, 2018 ).…”