Genome-Wide Identification of the PP2C Gene Family and Analyses with Their Expression Profiling in Response to Cold Stress in Wild Sugarcane.

Type 2C protein phosphatases (PP2Cs) represent a major group of protein phosphatases in plants, some of which have already been confirmed to play important roles in diverse plant processes. In this study, analyses of the phylogenetics, gene structure, protein domain, chromosome localization, and collinearity, as well as an identification of the expression profile, protein-protein interaction, and subcellular location, were carried out on the PP2C family in wild sugarcane (Saccharum spontaneum). The results showed that 145 PP2C proteins were classified into 13 clades. Phylogenetic analysis suggested that SsPP2Cs are evolutionarily closer to those of sorghum, and the number of SsPP2Cs is the highest. There were 124 pairs of SsPP2C genes expanding via segmental duplications. Half of the SsPP2C proteins were predicted to be localized in the chloroplast (73), with the next most common predicted localizations being in the cytoplasm (37) and nucleus (17). Analysis of the promoter revealed that SsPP2Cs might be photosensitive, responsive to abiotic stresses, and hormone-stimulated. A total of 27 SsPP2Cs showed cold-stress-induced expressions, and SsPP2C27 (Sspon.01G0007840-2D) and SsPP2C64 (Sspon.03G0002800-3D) were the potential hubs involved in ABA signal transduction. Our study presents a comprehensive analysis of the SsPP2C gene family, which can play a vital role in the further study of phosphatases in wild sugarcane. The results suggest that the PP2C family is evolutionarily conserved, and that it functions in various developmental processes in wild sugarcane.

A type-2C protein phosphatase (GhDRP1) participates in cotton (Gossypium hirsutum) response to drought stress.

KEY MESSAGE: GhDRP1 acts as a negatively regulator to participate in response to drought stress possibly by modulating ABA signaling pathway and flavonoid biosynthesis pathway which affects stomata movement and thus water loss, ROS scavenging enzymes, and proline accumulation in cotton. Type-2C protein phosphatases (PP2C) may play important roles in plant stress signal transduction. Here, we show the evidence that a cotton PP2C protein GhDRP1 participates in plant response to drought stress. GhDRP1 gene encodes an active type-2C protein phosphatase (PP2C) and its expression is significantly induced in cotton by drought stress. Compared with wild type, the GhDRP1 overexpression (OE) transgenic cotton and Arabidopsis displayed reduced drought tolerance, whereas GhDRP1-silenced (RNAi) cotton showed enhanced drought tolerance. Under drought stress, malondialdehyde content was lower, whereas superoxide dismutase and peroxidase activities, proline content, stomata closure and relative water content were higher in GhDRP1 RNAi plants compared with those in wild type. In contrast, GhDRP1 OE plants showed the opposite phenotype under the same conditions. Expression levels of some stress-related and flavonoid biosynthesis-related genes were altered in GhDRP1 transgenic plants under drought stress. Additionally, GhDRP1 protein could interact with other proteins such as PYLs, SNF1-related protein kinase and GLK1-like protein. Collectively, these data suggest that GhDRP1 participates in plant response to drought stress possibly by modulating ABA signaling pathway and flavonoid biosynthesis pathway which affects stomata movement and thus water loss, ROS scavenging enzymes, and proline accumulation in cotton.

Identification of the PP2C gene family in paper mulberry (Broussonetia papyrifera) and its roles in the regulation mechanism of the response to cold stress.

OBJECTIVES: To study the possible roles of type-2C protein phosphatases (PP2Cs) which have been confirmed to play roles in the response to diverse abiotic stresses in paper mulberry, we launched a series of genomic and functional studies of BpPP2Cs. RESULTS: Sixty-three PP2C proteins in paper mulberry (Broussonetia papyrifera) were classified into 13 clades. Four BpPP2Cs with kinase domains were verified to be highly conserved in organisms ranging from algae to dicots. Seven pairs of BpPP2C genes were found to be expanding, and 18 BpPP2C genes had orthologues in Arabidopsis. BpPP2Cs showed broad expression in different tissues; the expression levels of 18 BpPP2Cs were changed and the phosphorylation levels of seven BpPP2C proteins increased at low temperature. Cold-response elements were found in the promoter region of 31 BpPP2Cs. Finally, Bp01g0320 was found to act as a hub protein and Bp01g0512 and Bp09g1278 played key roles in the ABA-signaling pathway and MAPK cascades, respectively. CONCLUSION: These results suggest that the PP2C gene family of paper mulberry is evolutionarily conserved and participates the regulation of the response to cold stress, which will play a vital role in further research on phosphatases in paper mulberry.

Chromatin remodeling for the transcription of type 2C protein phosphatase genes in response to salt stress.

Type 2C protein phosphatases (PP2Cs) counteract protein kinases, thereby inhibiting the abscisic acid (ABA)-mediated response to abiotic stress in Arabidopsis thaliana. In the absence of stress, the promoters of PP2C genes (e.g., ABI1, ABI2, and HAI1) are negatively regulated by repressors that suppress gene transcription in a signal-independent manner. Quantitative reverse transcription PCR (RT-qPCR) and chromatin immunoprecipitation (ChIP) assays revealed that the levels of PP2C gene transcripts and RNA polymerase II (RNAPII) that stalled at the transcription start sites (TSS) of PP2C gene loci were increased under salt stress. The salt-induced increases in RNA polymerase-mediated transcription were reduced in 35S:AtMYB44 plants, confirming that AtMYB44 acts as a repressor of PP2C gene transcription. ChIP assays revealed that AtMYB44 repressors are released and nucleosomes are evicted from the promoter regions in response to salt stress. Under these conditions, histone H3 acetylation (H3ac) and methylation (H3K4me3) around the TSS regions significantly increased. The salt-induced increases in PP2C gene transcription were reduced in abf3 plants, indicating that ABF3 activates PP2C gene transcription. Overall, our data indicate that salt stress converts PP2C gene chromatin from a repressor-associated suppression status to an activator-mediated transcription status. In addition, we observed that the Arabidopsis mutant brm-3, which is moderately defective in SWI2/SNF2 chromatin remodeling ATPase BRAHMA (BRM) activity, produced more PP2C gene transcripts under salt stress conditions, indicating that BRM ATPase contributes to the repression of PP2C gene transcription.