Characterisation and natural variation of a dehydrin gene in Quercus petraea (Matt.) Liebl

AnDHN, a Dehydrin Protein From Ammopiptanthus nanus, Mitigates the Negative Effects of Drought Stress in Plants

Dehydrins (DHNs) play crucial roles in a broad spectrum of abiotic stresses in model plants. However, the evolutionary role of DHNs has not been explored, and the function of DHN proteins is largely unknown in Ammopiptanthus nanus (A. nanus), an ancient and endangered legume species from the deserts of northwestern China. In this study, we isolated a drought-response gene (c195333_g1_i1) from a drought-induced RNA-seq library of A. nanus. Evolutionary bioinformatics showed that c195333_g1_i1 is an ortholog of Arabidopsis DHN, and we renamed it AnDHN. Moreover, DHN proteins may define a class of proteins that are evolutionarily conserved in all angiosperms that have experienced a contraction during the evolution of legumes. Arabidopsis plants overexpressing AnDHN exhibited morpho-physiological changes, such as an increased germination rate, higher relative water content (RWC), higher proline (PRO) content, increased peroxidase (POD) and catalase (CAT) activities, lower contents of malondialdehyde (MDA), H₂O₂ and O₂ ^-, and longer root length. Our results showed that the transgenic lines had improved drought resistance with deep root system architecture, excellent water retention, increased osmotic adjustment, and enhanced reactive oxygen species (ROS) scavenging. Furthermore, the transgenic lines also had enhanced salt and cold tolerance. Our findings demonstrate that AnDHN may be a good candidate gene for improving abiotic stress tolerance in crops. Key Message: Using transcriptome analysis in Ammopiptanthus nanus, we isolated a drought-responsive gene, AnDHN, that plays a key role in enhancing abiotic stress tolerance in plants, with strong functional diversification in legumes.

Characterization of Dehydrin protein, CdDHN4-L and CdDHN4-S, and their differential protective roles against abiotic stress in vitro

BACKGROUND

Dehydrins play positive roles in regulating plant abiotic stress responses. The objective of this study was to characterize two dehydrin genes, CdDHN4-L and CdDHN4-S, generated by alternative splicing of CdDHN4 in bermudagrass.

RESULTS

Overexpression of CdDHN4-L with φ-segment and CdDHN4-S lacking of φ-segment in Arabidopsis significantly increased tolerance against abiotic stresses. The growth phenotype of Arabidopsis exposed to NaCl at 100 mM was better in plants overexpressing CdDHN4-L than those overexpressing CdDHN4-S, as well as better in E.coli cells overexpressing CdDHN4-L than those overexpressing CdDHN4-S in 300 and 400 mM NaCl, and under extreme temperature conditions at - 20 °C and 50 °C. The CdDHN4-L had higher disordered characterization on structures than CdDHN4-S at temperatures from 10 to 90 °C. The recovery activities of lactic dehydrogenase (LDH) and alcohol dehydrogenase (ADH) in presence of CdDHN4-L and CdDHN4-S were higher than that of LDH and ADH alone under freeze-thaw damage and heat. Protein-binding and bimolecular fluorescence complementation showed that both proteins could bind to proteins with positive isoelectric point via electrostatic forces.

CONCLUSIONS

These results indicate that CdDHN4-L has higher protective ability against abiotic stresses due to its higher flexible unfolded structure and thermostability in comparison with CdDHN4-S. These provided direct evidence of the function of the φ-segment in dehydrins for protecting plants against abiotic stress and to show the electrostatic interaction between dehydrins and client proteins.

Morpho-anatomical, physiological and biochemical changes in rubber tree seeds

The physical, physiological and biochemical changes during the development until the dispersal of rubber tree seeds were evaluated with the purpose of estimating the point at physiological maturity. A total of 30 plants were selected at different points in a commercial planting area and had their flowers marked during the anthesis and every 15 days after marking. Fruits and seeds were collected for analysis of moisture content, dry matter, diameter and length. Details of the anatomy ultra-structure of the seeds were evaluated. The seed emergence, emergency speed index, heat resistant proteins and oxidative stress enzymes were examined. It was observed that fruits reached maximum size at 120 days after anthesis and seeds at 150 days. The seeds acquired germination capacity after 150 days. At 175 days, they presented the highest percentage of dry matter and lowest moisture, in addition to a higher percentage of germination and vigor. Therefore, it was possible to conclude that the physiological maturity of the rubber tree seeds occurs at 175 days after anthesis, and coincides with its maximum physiological quality. At 175 and 180 days post-anthesis, there is a greater expression of heat resistant proteins as well as low molecular weight and greater oxidative stress enzyme activity.

The dehydrin wzy2 promoter from wheat defines its contribution to stress tolerance

Dehydrins (DHNs), which are stress-related proteins, are important for plant survival under various abiotic and biotic stresses. To elucidate the regulatory mechanisms of wheat-derived DHNs under these stresses, we characterized the DHN wzy2 promoter of the wheat cultivar Zhengyin 1 and studied its contribution to stress tolerance. Sequence analysis indicated that the wzy2 gene contains one 109-bp intron inserted in the nucleotide sequence encoding the S-motif and characterized by a GT-AG border. The wzy2 promoter was revealed to contain several potential stress-related cis-acting regulatory elements, including elements responsive to abscisic acid (ABA; ABREs), anoxia (GC motifs), low temperature (LTREs), auxin (TGA elements), methyl jasmonate (MeJA; TGACG motifs), and gibberellin (TATC boxes). Quantitative real-time PCR analysis showed that transcript accumulation occurred in response to low temperature, anoxia, indoleacetic acid, MeJA, ABA, and gibberellin (GA) treatments. Histochemical analysis of GUS expression demonstrated that wzy2 promoter activity could be upregulated by low temperature, anoxia, ABA, and GA treatments. Interestingly, wzy2 promoter element-driven β-glucuronidase expression was first observed in meristemoids rather than calli of wheat seeds subjected to anoxia. Taken together, these results indicate that YSK2-type wzy2 can be induced directly by ABA, low temperature, anoxia, and GA treatments and indirectly by drought, implying that different cis-acting elements interact in stress response cross talk.

Bioclimatic regions influence genetic structure of four Jordanian Stipa species

Strong environmental gradients can affect the genetic structure of plant populations, but little is known as to whether closely related species respond similarly or idiosyncratically to ecogeographic variation. We analysed the extent to which gradients in temperature and rainfall shape the genetic structure of four Stipa species in four bioclimatic regions in Jordan. Genetic diversity, differentiation and structure of Stipa species were investigated using amplified fragment length polymorphism (AFLP) molecular markers. For each of the four study species, we sampled 120 individuals from ten populations situated in distinct bioclimatic regions and assessed the degree of genetic diversity and genetic differentiation within and among populations. The widespread ruderals Stipa capensis and S. parviflora had higher genetic diversity than the geographically restricted semi-desert species S. arabica and S. lagascae. In three of the four species, genetic diversity strongly decreased with precipitation, while genetic diversity increased with temperature in S. capensis. Most genetic diversity resided among populations in the semi-desert species (Φ(ST) = 0.572/0.595 in S. arabica/lagascae) but within populations in the ruderal species (Φ(ST) = 0.355/0.387 S. capensis/parviflora). Principal coordinate analysis (PCoA) and STRUCTURE analysis showed that Stipa populations of all species clustered ecogeographically. A genome scan revealed that divergent selection at particular AFLP loci contributed to genetic differentiation. Irrespective of their different life histories, Stipa species responded similarly to the bioclimatic gradient in Jordan. We conclude that, in addition to predominant random processes, steep climatic gradients might shape the genetic structure of plant populations.

Characterization of two novel cold-inducible K3 dehydrin genes from alfalfa (Medicago sativa spp. sativa L.)

Dehydrin defines a complex family of intrinsically disordered proteins with potential adaptive value with regard to freeze-induced cell dehydration. Search within an expressed sequence tags library from cDNAs of cold-acclimated crowns of alfalfa (Medicago sativa spp. sativa L.) identified transcripts putatively encoding K(3)-type dehydrins. Analysis of full-length coding sequences unveiled two highly homologous sequence variants, K(3)-A and K(3)-B. An increase in the frequency of genotypes yielding positive genomic amplification of the K(3)-dehydrin variants in response to selection for superior tolerance to freezing and the induction of their expression at low temperature strongly support a link with cold adaptation. The presence of multiple allelic forms within single genotypes and independent segregation indicate that the two K(3) dehydrin variants are encoded by distinct genes located at unlinked loci. The co-inheritance of the K(3)-A dehydrin with a Y(2)K(4) dehydrin restriction fragment length polymorphism with a demonstrated impact on freezing tolerance suggests the presence of a genome domain where these functionally related genes are located. These results provide additional evidence that dehydrin play important roles with regard to tolerance to subfreezing temperatures. They also underscore the value of recurrent selection to help identify variants within a large multigene family in allopolyploid species like alfalfa.

Genome-wide analysis and identification of HAK potassium transporter gene family in maize (Zea mays L.)

The high-affinity K(+) (HAK) transporter gene family constitutes the largest family that functions as potassium transporter in plant and is important for various cellular processes of plant life. In spite of their physiological importance, systematic analyses of ZmHAK genes have not yet been investigated. In this paper, we indicated the isolation and characterization of ZmHAK genes in whole-genome wide by using bioinformatics methods. A total of 27 members (ZmHAK1-ZmHAK27) of this family were identified in maize genome. ZmHAK genes were distributed in all the maize 10 chromosomes. These genes expanded in the maize genome partly due to tandem and segmental duplication events. Multiple alignment and motif display results revealed major maize ZmHAK proteins share all the three conserved domains. Phylogenetic analysis indicated ZmHAK family can be divided into six subfamilies. Putative cis-elements involved in Ca(2+) response, abiotic stress adaption, light and circadian rhythms regulation and seed development were observed in the promoters of ZmHAK genes. Expression data mining suggested maize ZmHAK genes have temporal and spatial expression pattern. In all, these results will provide molecular insights into the potassium transporter research in maize.