Abstract
BackgroundOrnithine aminotransferase (OAT, EC:2.6.1.13), alternatively known as ornithine delta aminotransferase (δOAT), is a pyridoxal phosphate (PLP)-dependent enzyme involved in the conversion of ornithine into glutamyl-5-semi-aldehyde (GSA) and vice versa. Up till now, there has been no study on OAT in wheat despite the success of its isolation from rice, maize, and sorghum. This study focuses on identification and molecular characterization of OAT in wheat.ResultsIn total, three homeologous OAT genes in wheat genome were found on chromosome group 5, named as TaOAT-5AL, TaOAT-5BL, and TaOAT-5DL. Sequence alignment between gDNA and its corresponding cDNA obtained a total of ten exons and nine introns. A phylogenetic tree was constructed and results indicated that OATs shared highly conserved domains between monocots and eudicots, which was further illustrated by using WebLogo to generate a sequence logo. Further subcellular localization analysis indicated that they functioned in mitochondria. Protein-protein interactions supported their role in proline biosynthesis through interactions with genes, such as delta 1-pyrroline-5-carboxylate synthetase (P5CS) and pyrroline-5-carboxylate reductase (P5CR), involved in the proline metabolic pathway. Promoter analysis exposed the presence of several stress responsive elements, implying their involvement in stress regulation. Expression profiling illustrated that TaOAT was highly induced in the wheat plants exposed to drought or salt stress condition. Upregulated expression of TaOATs was observed in stamens and at the heading stage. A potential role of TaOAT genes during floret development was also revealed. Furthermore, the transgenic plants overexpressing TaOAT showed enhanced tolerance to drought stress by increasing proline accumulation. In addition, salt tolerance of the transgenic plants was also enhanced.ConclusionTaOATs genes were involved in proline synthesis and nitrogen remobilization because they interacted with genes related to proline biosynthesis enzymes and arginine catabolism. In addition, TaOAT genes had a role in abiotic stress tolerance and a potential role in floret development. The results of this study may propose future research in the improvement of wheat resistance to abiotic stresses.
Highlights
Ornithine aminotransferase (OAT, EC:2.6.1.13), alternatively known as ornithine delta aminotransferase, is a pyridoxal phosphate (PLP)-dependent enzyme involved in the conversion of ornithine into glutamyl-5semi-aldehyde (GSA) and vice versa
Isolation and structure analysis of TaOAT genes in hexaploid wheat Sequence retrieval from the International Wheat Genome Sequencing Consortium (IWGSC) database using AtOAT accession At5g46180 as query resulted in a total of three scaffolds that matched our query, namely, TGACv1_scaffold_374190, TGACv1_scaffold_404925, and TGACv1_scaffold_435304, which were located on the long arm of chromosome group 5 with e-values of 1e-30, 7e-27 and 4e-24, respectively
We found that TaOAT-5AL-2 had higher identity to TRIDC5AG054810.2
Summary
Ornithine aminotransferase (OAT, EC:2.6.1.13), alternatively known as ornithine delta aminotransferase (δOAT), is a pyridoxal phosphate (PLP)-dependent enzyme involved in the conversion of ornithine into glutamyl-5semi-aldehyde (GSA) and vice versa. There has been no study on OAT in wheat despite the success of its isolation from rice, maize, and sorghum. This study focuses on identification and molecular characterization of OAT in wheat. Wheat (Triticum aestivum) is a worldwide cultivated crop and accounts for 20% of the calories consumed by humans [1]. Improving wheat yield, especially under increasing abiotic stresses, is necessary to alleviate the situation. Plants have evolved a complex system to survive abiotic stresses via changes at the morphological, physiological and molecular levels [2, 3]. The limitations in the wheat germplasm ( known as wheat gene resources) has restricted the development of wheat varieties with abiotic stress tolerance. It is necessary to identify more stress-related genes which can be utilized in breeding programs to develop stresstolerant wheat varieties
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