Brachypodium distachyon BdPP2CA6 Interacts with BdPYLs and BdSnRK2 and Positively Regulates Salt Tolerance in Transgenic Arabidopsis

Abstract

The phytohormone abscisic acid (ABA) is essential in plant responding to biotic and abiotic stresses. Although ABA signaling model is well established in Arabidopsis, ABA receptor PYL family and clade A PP2C subfamily are not yet characterized in monocot model plant Brachypodium distachyon. In this study, we identified 12 PYLs and 8 clade A PP2Cs from B. distachyon genome and successfully cloned 12 PYLs and 7 clade A PP2Cs. Bioinformatic and expression analyses showed that most of the identified genes respond to several signal molecules and abiotic stresses. Protein–protein interaction analysis revealed that many BdPYLs and BdPP2CAs participate in the classic ABA-PYL-PP2C-SnRK2 signaling pathway. A clade A PP2C, designated BdPP2CA6, interacted with BdPYL11 in the absence of ABA and localized in nucleus. Most clade A PP2C members from Arabidopsis showed negatively regulation in ABA signaling pathway, whereas BdPP2CA6-overexpression transgenic Arabidopsis showed ABA hypersensitive phenotype, resulting in enhanced stomatal closure and salinity tolerance. Our results indicate that BdPP2CA6 positively regulates ABA and stress signal pathway in transgenic Arabidopsis plant seedlings.

Non‐redundant functions of the dimeric ABA receptor BdPYL1 in the grass Brachypodium

“…Based on low overall amino acid homology (10-20%), specifically in the gate and latch loop sections ( Figure S1), we suggest that the latter are not ABA receptors. This hypothesis is strengthened by the lack of interaction of these three proteins and PP2Cs, as presented by Zhang et al (2017). In eudicots such as A. thaliana and tomato, phylogenetic analysis of receptors revealed three distinct subfamilies (Ma et al, 2009;Park et al, 2009;Gonzalez-Guzman et al, 2014).…”

“…This hypothesis is strengthened by the lack of interaction of these three proteins and PP2Cs, as presented by Zhang et al . ().…”

“…Genome‐wide domain analysis performed by Zhang et al . () resulted in 12 START domain proteins annotated as PYR/L ABA receptors. However, further sequence analysis performed here does not concur with this assumption for three out of the 12 proteins (encoded by BRADI2G32950, BRADI2G48630, BRADI2G62090 ).…”

“…In the current study, we identified nine functional ABA receptors and one additional receptor-BdPYL10, which is likely to be a pseudo gene. Recently, two papers describing the ABA pathway of B. distachyon were published, both studies focused on the PP2C co-receptor (Cao et al, 2016;Zhang et al, 2017). Genome-wide domain analysis performed by Zhang et al (2017) resulted in 12 START domain proteins annotated as PYR/ L ABA receptors.…”

“…Recently, two papers describing the ABA pathway of B. distachyon were published, both studies focused on the PP2C co-receptor (Cao et al, 2016;Zhang et al, 2017). Genome-wide domain analysis performed by Zhang et al (2017) resulted in 12 START domain proteins annotated as PYR/ L ABA receptors. However, further sequence analysis performed here does not concur with this assumption for three out of the 12 proteins (encoded by BRADI2G32950, BRADI2G48630, BRADI2G62090).…”