Identification of PP2C Genes in Tibetan Hulless Barley (Hordeum vulgare var. nudum) Under Dehydration Stress and Initiatory Expression and Functional Analysis of HvPP2C59

Protein phosphatase 2Cs (PP2Cs) are negative regulators in the classic abscisic acid (ABA)-mediated drought stress signaling network. However, some members of PP2Cs can regulate the resistant to abiotic stresses positively, which provided a new way to solve the problem of low yield under severe environment. PP2C genes have been studied in many plants, but not been reported in Tibetan hulless barley, which survived from harsh environment and can be used as a good subject for analyzing drought tolerance mechanism. Fifty-four PP2C genes were identified in hulless barley under dehydration stress from our previous RNA-Seq data. Of these PP2Cs, 12 were significantly induced under dehydration stress and may be considered drought resistance candidate genes. Phylogenetic study showed that these HvPP2Cs can be classified into 12 major clusters (group A-I, K-M). HvPP2C59, which belongs to group F, showed remarkable continuously upregulated pattern during dehydration stress, was cloned in this study. Bioinformatics analysis identified motifs such as ABRE, MeJA, and G-box (light responsiveness) within its promoter region. Expression analysis indicated that HvPP2C59 can be promoted under drought, NaCl, and polyethylene glycol (PEG) 6000 stress, suppressed under dark, but was almost unaffected with ABA treatment. HvPP2C59-silenced plants had higher leaf water loss rate (WLR) and lower survival rate (SR) compared with controls under dehydration stress. The silenced plants also showed retarded vegetative growth under normal condition. Silencing of HvPP2C59 resulted in restrained expression of cold-regulated gene, LEA genes, and JA bio-synthesis key gene AOC. The study of PP2C genes in hulless barley will provide practical support to further expound the specific mechanism of plant response to drought stress.

Automated summary

This study identified 54 PP2C genes in Tibetan hulless barley and found that 12 of them were significantly induced under dehydration stress. HvPP2C59, belonging to group F, showed a remarkable continuously upregulated pattern during dehydration stress. Silencing HvPP2C59 gene resulted in increased leaf water loss rate, decreased survival rate, and retarded vegetative growth in hulless barley.