Abiotic stresses have severe detrimental effects on agricultural productivity worldwide. Abscisic acid (ABA) levels rise in response to abiotic stresses, and play a role in coordinating physiological responses. ABA elicits its effects by binding a family of soluble receptors, increasing affinity of the receptors to type 2C phosphatases (PP2Cs) leading to phosphatase inhibition. In the current study, we conducted a comprehensive analysis of the ABA signaling pathway in the cereal model grass Brachypodium distachyon. The Brachypodium genome encodes a family of 10 functionally conserved ABA receptors. The 10th in the series, BdPYL10, encodes a defective receptor and is likely a pseudogene. Combinatorial protein interaction assay further validated computational analysis, which grouped Brachypodium ABA receptors into three subfamilies, similarly to Arabidopsis classification. Brachypodium subfamily III receptors inhibited PP2C activity in vitro and complemented Arabidopsis quadruple (pyr1/pyl1/pyl2/pyl4) mutant. BdPYL1 T-DNA mutant exhibited clear ABA hyposensitivity phenotypes during seedling establishment and in mature plants. Single receptor predominance is in agreement with high transcriptional abundance of only a small Brachypodium ABA receptors subset, harboring the higher marginal significance of BdPYL1. Our findings suggest that unlike the highly redundant ABA core signaling components of Arabidopsis, Brachypodium encompasses a more compact and specialized ABA receptor apparatus. This organization may contribute to plant adaptations to ecological niches. These results lay the groundwork for targeting the prominent ABA receptors for stress perception in grasses, and reveal functional differences and commonalities between monocots and eudicots.
Bibliographical noteFunding Information:
The authors thank Prof. Sean Cutler for kindly providing the quadruple A. thaliana pyr1/pyl1/pyl2/pyl4 mutant and ABI1G180D related plasmids, David Weiss for comments on the manuscript, Rafael Yaari for his valuable bioinformatics assistance, and Alon Samach for his helpful comments and discussions. This work was supported in part by the ISF Israel Science Foundation (1069/14). L.S.M. is indebted to the Israeli President’s Scholarship for Scientific Excellence and Innovation.
© 2017 The Authors The Plant Journal © 2017 John Wiley & Sons Ltd
- Brachypodium distachyon
- abscisic acid
- abscisic acid signaling
- type 2C phosphatases