Zhang Jing, Wang Yongxu, Zhang Susu, Zhang Shuhui, Liu Wenjun, Wang Nan, Fang Hongcheng, Zhang Zongying, Chen Xuesen
College of Chemistry and Material Science, Shandong Agricultural University, Tai'an, 271018, Shandong, China.
Shandong Institute of Pomology, Shandong Academy Agricultural Sciences, Tai'an, 271000, Shandong, China.
Hortic Res. 2024 Aug 8;11(10):uhae215. doi: 10.1093/hr/uhae215. eCollection 2024 Oct.
Fruit aroma is an important organoleptic quality, which influences consumer preference and market competitiveness. Aroma compound synthesis pathways in plants have been widely identified, among the lipoxygenase pathway is crucial for fatty acid catabolism to form esters in apple. However, the regulatory mechanism of this pathway remains elusive. In this study, linear regression analysis and transgene verification revealed that the lipoxygenase MdLOX1a is involved in ester biosynthesis. Yeast one-hybrid library screening indicated that a protein, MdASG1 (ABIOTIC STRESS GENE 1), was a positive regulator of and ester production based on yeast one-hybrid and dual-luciferase assays, as well as correlation analysis among eight different apple cultivars. Overexpression of in apple and tomato stimulated the lipoxygenase pathway and increased the fatty acid-derived volatile content, whereas the latter was decreased by silencing and CRISPR/Cas9 knockout. Furthermore, overexpression enhanced the salt-stress tolerance of tomato and apple 'Orin' calli accompanied by a higher content of fatty acid-derived volatiles compared to that of non-stressed transgenic tomato fruit, while -Cas9 knockdown calli do not respond to salt stress and promote the biosynthesis of fatty acid-derived volatiles. Collectively, these findings indicate that MdASG1 activates expression and participates in the lipoxygenase pathway, subsequently increasing the accumulation of aroma compounds, especially under moderate salt stress treatment. The results also provide insight into the theory for improving fruit aroma quality in adversity.
水果香气是一种重要的感官品质，它影响消费者的偏好和市场竞争力。植物中的香气化合物合成途径已被广泛鉴定，其中脂氧合酶途径对于苹果中脂肪酸分解代谢形成酯类至关重要。然而，该途径的调控机制仍不清楚。在本研究中，线性回归分析和转基因验证表明脂氧合酶MdLOX1a参与酯类生物合成。酵母单杂交文库筛选表明，基于酵母单杂交和双荧光素酶测定以及八个不同苹果品种之间的相关性分析，一种名为MdASG1（非生物胁迫基因1）的蛋白质是酯类产生的正调控因子。在苹果和番茄中过表达MdASG1会刺激脂氧合酶途径并增加脂肪酸衍生的挥发性物质含量，而通过沉默和CRISPR/Cas9敲除MdASG1则会降低其含量。此外，与未受胁迫的转基因番茄果实相比，MdASG1过表达增强了番茄和苹果‘奥瑞’愈伤组织对盐胁迫的耐受性，同时脂肪酸衍生的挥发性物质含量更高，而MdASG1-Cas9敲除愈伤组织对盐胁迫无反应并促进脂肪酸衍生的挥发性物质的生物合成。总的来说，这些发现表明MdASG1激活MdLOX1a的表达并参与脂氧合酶途径，随后增加香气化合物的积累，特别是在中度盐胁迫处理下。这些结果也为逆境中改善果实香气品质的理论提供了见解。
