Cloning and molecular characterization of Triticum aestivum ornithine amino transferase (TaOAT) encoding genes

Improving Wheat Salt Tolerance for Saline Agriculture

Salinity is a major abiotic stress that threatens crop yield and food supply in saline soil areas. Crops have evolved various strategies to facilitate survival and production of harvestable yield under salinity stress. Wheat (Triticum aestivum L.) is the main crop in arid and semiarid land areas, which are often affected by soil salinity. In this review, we summarize the conventional approaches to enhance wheat salt tolerance, including cross-breeding, exogenous application of chemical compounds, beneficial soil microorganisms, and transgenic engineering. We also propose several new breeding techniques for increasing salt tolerance in wheat, such as identifying new quantitative trait loci or genes related to salt tolerance, gene stacking and multiple genome editing, and wheat wild relatives and orphan crops domestication. The challenges and possible countermeasures in enhancing wheat salinity tolerance are also discussed.

Expression of Arabidopsis Ornithine Aminotransferase (AtOAT) encoded gene enhances multiple abiotic stress tolerances in wheat

The drought and salt tolerances of wheat were enhanced by ectopic expression of the Arabidopsis ornithine aminotransferase (AtOAT) encoded gene. The OAT was confirmed to play a role in proline biosynthesis in wheat. Proline (Pro) accumulation is a common response to both abiotic and biotic stresses in plants. Ornithine aminotransferase (OAT) is pyridoxal-5-phosphate dependent enzyme involved in plant proline biosynthesis. During stress condition, proline is synthesized via glutamate and ornithine pathways. The OAT is the key enzyme in ornithine pathway. In this study, an OAT gene AtOAT from Arabidopsis was expressed in wheat for its functional characterization under drought, salinity, and heat stress conditions. We found that the expression of AtOAT enhanced the drought and salt stress tolerances of wheat by increasing the proline content and peroxidase activity. In addition, it was confirmed that the expression of AtOAT also played a partial tolerance to heat stress in the transgenic wheat plants. Moreover, quantitative real-time PCR (qRT-PCR) analysis showed that the transformation of AtOAT up-regulated the expression of the proline biosynthesis associated genes TaOAT, TaP5CS, and TaP5CR, and down-regulated that of the proline catabolism related gene TaP5CDH in the transgenic plants under stress conditions. Moreover, the genes involved in ornithine pathway (Orn-OAT-P5C/GSA-P5CR-Pro) were up-regulated along with the up-regulation of those genes involved in glutamate pathway (Glu-P5CS-P5C/GSA-P5CR-Pro). Therefore, we concluded that the expression of AtOAT enhanced wheat abiotic tolerance via modifying the proline biosynthesis by up-regulating the expression of the proline biosynthesis-associated genes and down-regulating that of the proline catabolic gene under stresses condition.

Identification of Ipomoea batatas anti-cancer peptide (IbACP)-responsive genes in sweet potato leaves

IbACP, Ipomoea batatas anti-cancer peptide, a sixteen-amino-acid peptide isolated from sweet potato leaves, is capable of mediating a rapid alkalinization of growth media in plant suspension cells. However, the biological roles of IbACP as a defense peptide have not been studied. The objective of this study was to investigate the effect of IbACP on the accumulation of reactive oxygen species (ROS) and the expression of the defense-related genes. IbACP treatment of sweet potato leaves resulted in marked accumulation of both superoxide ion (O₂^-) and hydrogen peroxide (H₂O₂). The activity of peroxidase (POD) was significantly enhanced by IbACP treatment, suggesting that high levels of POD antioxidant activity may be used to scavenge the excess H₂O₂ in sweet potato plants. The IbACP-related genes were identified by suppression subtractive hybridization (SSH), and were then classified and assigned to the following categories: defense, development, metabolism, signaling, gene expression, and abiotic stress. H₂O₂ acts as a second messenger for gene activation in some of the IbACP-triggered gene expressions. These results demonstrated that IbACP is part of an integrated strategy for genetic regulation in sweet potato. Our work highlights the function of IbACP and its potential use for enhancing stress tolerance in sweet potato, in an effort to improve our understanding of defense-response mechanisms.