Identification of different ABA biosynthesis sites at seedling and fruiting stages in Arachis hypogaea L. following water stress

摘要

Abscisic acid (ABA) is one of the most important phytohormones involved in abiotic stress responses. ABA transport in plants is important in determining endogenous ABA levels and their resulting physiological responses. However, the regulation of ABA transport remains unclear. In this study, we compared the ABA concentrations and AhNCED1 levels at seedling and fruiting stages in peanut (Arachis hypogaea L.), in response to water stress. At the seedling stage, ABA initially accumulated in roots (1 h), followed by the lower stem (2 h) and finally in the upper stem (4 h). The expression/activity of an ABA biosynthesis rate-limiting enzyme, AhNCED1, showed the same accumulation patterns. In contrast, during the fruiting stage, ABA and AhNCED1 increases were initially detected in the first apical leaf of main stem, followed by the stem, and finally in the root. These results imply that biosynthesis of ABA in peanut plants subject to water deficiency could be dependent on developmental stage with the roots being the initial site of ABA biosynthesis during the seedling stage, whereas during the fruiting stage ABA biosynthesis occurs initially in the leaf. The distribution patterns of ABA in seedling stage peanuts in response to water stress were: root-stem-leaf, while in fruiting stage peanuts the distribution patterns of ABA were: leaf-stem-root. These findings will help to understand plant regulatory water deficit resistance mechanisms at seedling and fruiting stages and to advance our total understanding of the regulation of ABA transport.