Expression analysis of dehydrin multigene family across tolerant and susceptible barley (Hordeum vulgare L.) genotypes in response to terminal drought stress

Dehydrins are one of the characteristic families of plant proteins that usually accumulate in response to drought. In the present study, gene expressions of dehydrin multigene family (13 genes) were examined in flag leaves of tolerant (Yousef) and susceptible (Moroco) barley varieties under terminal drought to characterize the involvement of dehydrins in the adaptive processes. The stomatal conductance, RWC, and Chl a, b contents had more reduction in Moroco than the Yousef which has more elevated osmotic adjustment. Drought stress increased significantly MDA and electrolyte leakage levels, but greater in Moroco, indicating a poor protection of cell and cytoplasmic membrane in this variety. Yousef variety had no reduction in grain yield under drought condition. Five genes (Dhn1, Dhn3, Dhn5, Dhn7 and Dhn9) were exclusively induced in Yousef under drought stress. In the stress condition, relative gene expression of Dhn3, Dhn9 had the direct correlations (P < 0.05) with Chl a, b contents, osmotic adjustment, stomatal conductance, plant biomass and grain yield, and the negative correlations (P < 0.05) with MDA and electrolyte leakage levels. The results supported the impending functional roles of dehydrin K_n and particularly Y_nSK_n types in dehydration tolerance of barley during the reproductive stage.     

Plant dehydrins: shedding light on structure and expression patterns of dehydrin gene family in barley

Dehydrins, an important group of late embryogenesis abundant proteins, accumulate in response to dehydration stresses and play protective roles under stress conditions. Herein, phylogenetic analysis of the dehydrin family was performed using the protein sequences of 108 dehydrins obtained from 14 plant species based on plant taxonomy and protein subclasses. Sub-cellular localization and phosphorylation sites of these proteins were also predicted. The protein features distinguishing these dehydrins categories were identified using various attribute weighting and decision tree analyses. The results revealed that the presence of the S motif preceding the K motif (Y_nSK_n, SK_n, and S_nKS) was more evident and the Y_nSK_n subclass was more frequent in monocots. In barley, as one of the most drought-tolerant crops, there are ten members of Y_nSK_n out of 13 HvDhns. In promoter regions, six types of abiotic stress-responsive elements were identified. Regulatory elements in UTR sequences of HvDhns were infrequent while only four miRNA targets were found. Furthermore, physiological parameters and gene expression levels of HvDhns were studied in tolerant (HV1) and susceptible (HV2) cultivars, and in an Iranian tolerant wild barley genotype (Spontaneum; HS) subjected to gradual water stress and after recovery duration at the vegetative stage. The results showed the significant impact of dehydration on dry matter, relative leaf water, chlorophyll contents, and oxidative damages in HV2 compared with the other studied genotypes, suggesting a poor dehydration tolerance, and incapability of recovering after re-watering in HV2. Under severe drought stress, among the 13 HvDhns genes, 5 and 10 were exclusively induced in HV1 and HS, respectively. The gene and protein structures and the expression patterns of HvDhns as well as the physiological data consistently support the role of dehydrins in survival and recovery of barley plants from drought particularly in HS. Overall, this information would be helpful for functional characterization of the Dhn family in plants.