COP1 promotes ABA‐induced stomatal closure by modulating the abundance of ABI/HAB and AHG3 phosphatases

Abstract

 Plant stomata are crucial to control water transpiration in response to environmental stresses and to modulate gas exchange necessary for photosynthesis. The phytohormone ABA promotes stomatal closure and inhibits light-induced stomatal opening. The Arabidopsis thaliana E3 ubiquitin ligase COP1 functions in ABA-mediated stomatal closure. However, the underlying molecular mechanisms are still not fully understood.  Yeast two-hybrid assays were used to identify ABA signaling components that interact with COP1, and biochemical, molecular and genetic studies were carried out to elucidate the regulatory role of COP1 in ABA signaling.  The cop1 mutants are hyposensitive to ABA-triggered stomatal closure under light and dark conditions. COP1 interacts with and ubiquitinates the Arabidopsis thaliana Clade A type 2C phosphatases (PP2Cs) ABI/HAB group and AHG3, thus triggering their degradation. ABA enhances the COP1-mediated degradation of these PP2Cs. Mutations in ABI1 and AHG3 partly rescue the cop1 stomatal phenotype and the phosphorylation level of OST1, a crucial Accepted Article This article is protected by copyright. All rights reserved SnRK2-type kinase in ABA signaling.  Our data indicate that COP1 is part of a novel signaling pathway promoting ABA-mediated stomatal closure by regulating the stability of a subset of the Clade A PP2Cs. These findings provide novel insights into the interplay between ABA and the light signaling component in the modulation of stomatal movement.

Morpho-Physiological and Transcriptome Changes in Tomato Anthers of Different Developmental Stages under Drought Stress

“…In the PMC-MEI anthers, Slcyp707a1, encoding ABA 8′-hydroxylase involved in ABA catabolism, was markedly up-regulated. The core components of ABA signaling genes including one ABA receptor SlPYL9 , two protein phosphatase 2C (PP2C) genes, ABA insensitive 2 ( SlABI2 ) and ABA-hypersensitive germination 3 ( SlAHG3 ) [ 51 , 52 ], and two SNF1-Related Protein Kinase2 ( SnRK2 ) genes ( SlSRK2C and AY222455 ) were likewise significantly up-regulated ( Figure 7 B). Additionally, two known direct downstream targets of SnRK2, SlAREB2 (homologue of AtAREB2 ) and SlABF3 (homologue of AtABF3 ) ( Figure S5B ), were exclusively significantly up-regulated in PMC-MEI anthers, suggesting that ABA signaling is induced early during another development under drought stress.…”

Illuminating the COP1/SPA Ubiquitin Ligase: Fresh Insights Into Its Structure and Functions During Plant Photomorphogenesis

“…COP1 directly interacts and facilitates the degradation of type 2C phosphatases (PP2Cs), which are ABA coreceptors that positively regulate stomatal opening in the absence of ABA. By degrading PP2Cs, COP1 promotes stomatal closure and acts together with ABA (Chen et al, 2020). The COP1interacting protein CIP1 has also been reported to promote ABA signaling, but further details remain unknown (Ren et al, 2016).…”

“…Accordingly, cop1 mutants accumulate higher levels of ICE1 proteins in the nuclei of abaxial leaf epidermal cells, suggesting that the interaction partners of the COP1/SPA complex may vary according to the tissue types. In addition to stomatal differentiation, COP1 promotes ABA-mediated stomatal closure (Chen et al, 2020) and functions as an important regulator of abiotic stress in plants (Moazzam-Jazi et al, 2018). The role of COP1 in biotic stresses has also been documented.…”

Control of ABA Signaling and Crosstalk with Other Hormones by the Selective Degradation of Pathway Components

“…It is not clear whether so few Ub ligases controlling SnRK2s results from the paucity of experimental data, or if this signaling step is weakly controlled at the level of protein ubiquitination. [30]; REA1 [31]; PUB22 [32]; PUB23 [32] RCAR3/PYL8 RIFP1 [33]; DDA1 [30] RCAR10/PYL4 DDA1 [30]; RSL1 [34]; UBC26 (E2)-RFA4 (E3) [35]; RFA1 [35] RCAR11/PYR1 RSL1 [34]; RFA1 [35]; RFA4 [35] Type 2C protein phosphatases (PP2C) ABI1 PUB12 [36]; PUB13 [36]; BPM3 [37]; BPM5 [37]; UBC27/AIRP3 [38]; COP1 [39] ABI2 RGLG1 [40]; RGLG5 [40] HAB1 BPM3 [37]; BPM5 [37] HAB2/NHL29 RGLG1 [40]; RGLG5 [40] AHG1 PIR1.2 [41]; PIR2 [41] AHG3/PP2CA RGLG1 [40]; RGLG5 [40]; PIR1.2 [41]; PIR2 [41]; COP1 [39]; BPM3 [37]; BPM5 [37] HAI1/SAG113 PIR1. usually limited to a single functional group of the ABA signaling pathway.…”