Abiotic stresses (非生物胁迫) have severe detrimental (有害的) 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 (引出) its effects by binding a family of soluble receptors (可溶性受体), increasing affinity (亲和) of the receptors to type 2C phosphatases (PP2Cs; 2C磷酸酶) 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 (二穗短柄草). The Brachypodium genome encodes a family of 10 functionally conserved ABA receptors. The 10th in the series, BdPYL10, encodes a defective (有缺陷的) receptor and is likely a pseudogene. Combinatorial protein interaction assay (蛋白质相互作用分析) further validated computational analysis (计算分析), which grouped Brachypodium ABA receptors into three subfamilies, similarly to Arabidopsis classification. Brachypodium subfamily III receptors inhibited PP2C activity in vitro (体外) and complemented Arabidopsis quadruple (pyr1/pyl1/pyl2/pyl4) mutant. BdPYL1 T-DNA mutant exhibited clear ABA hyposensitivity (低敏感性) 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 (小生境). These results lay the groundwork (基础) for targeting the prominent ABA receptors for stress perception in grasses, and reveal functional differences and commonalities (共性) between monocots and eudicots.

First Published online: October 16, 2017.