| Hulless barley(Hordeum vulgare L.var.nudum Hook.f.)is the most characteristic crop in the Tibetan Plateau region,and it has an important position in the agricultural history,culture and economic development of the Tibetan Plateau.The growth and production of hulless barley are still subject to multiple abiotic stresses such as low temperature,drought,salinity,alkali and barrenness in the Tibetan plateau region.Nicotinamide is an amide compound of nicotinic acid.Nicotinamide is a precursor to the synthesis of lysergic acid and is also directly involved in the transport,distribution and storage of metal ions,especially iron ions,in plants,and plays a crucial role in antioxidant,growth and development control,and response to various abiotic stresses.In this study,the nicotinamide synthase gene HvnNAS1 and its promoter fragment were cloned from the hulless barley variety "Kunlun 14",and the structural characteristics of the gene and protein were analyzed.We also investigated its function and expression pattern under salinity,alkali,drought,and low nitrogen conditions.This result was laid for a deeper understanding of the study of nicotinamide resistance mechanisms in a variety of abiotic stresses.It provides a basis for solving multiple adversity stresses and quality improvement faced in hulless barley production by means of molecular breeding.The results of the study are as follows:(1)The sequence of HvnNAS1 gene and its promoter fragment of hulless barley were identical to that of barley Hv NAS1.The promoter fragment of hulless barley HvnNAS1 gene has more abscisic acid and jasmonic acid induced expression elements.The HvnNAS1 protein consists of 267 amino acids,is a hydrophobic stable protein with no transmembrane structure,has two serines,one threonine and two tyrosines for a total of five phosphorylation sites,and does not have a signal peptide.The secondary structure of HvnNAS1 protein has α-helix,β-turn angle,extended chain,and irregular coiling accounting for 54.68%,0.00%,12.36%,and 29.59% of the total amino acids,respectively,and Hv NAS1 has the closest affinity to Hv NAS3.(2)The expression patterns of HvnNAS1 in different tissues and under salinity,alkali,drought,and low nitrogen stresses were analyzed.The results showed that HvnNAS1 was expression in plant roots only,which was consistent with the results obtained from the barley database.Salinity and alkali stress can induce HvnNAS1 expression in the roots only,but not in the leaves.Subcellular localization results showed that HvnNAS1 was localized in the cytoplasm.(3)The overexpression vector of HvnNAS1 was constructed and transferred into Arabidopsis thaliana,and the resistance of transgenic plants to abiotic stresses like salinity,alkali,drought and low nitrogen stresses was investigated.The results showed that the transgenic plants were significantly better than wild-type plants in seed germination rate,growth status and biomass under salinity,alkali,drought and low nitrogen stresses,indicating that overexpression of HvnNAS1 in Arabidopsis thaliana could improve the resistance to salinity,alkali,drought and low nitrogen stresses. |
