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 MdLOX1a and ester production based on yeast one-hybrid and dual-luciferase assays, as well as correlation analysis among eight different apple cultivars. Overexpression of MdASG1 in apple and tomato stimulated the lipoxygenase pathway and increased the fatty acid-derived volatile content, whereas the latter was decreased by MdASG1 silencing and CRISPR/Cas9 knockout. Furthermore, MdASG1 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 MdASG1-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 MdLOX1a 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.

中文翻译：

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非生物胁迫基因 1 通过激活苹果中的 MdLOX1a 介导香气挥发物积累


水果香气是一种重要的感官品质，它影响着消费者的偏好和市场竞争力。植物中的芳香化合物合成途径已被广泛发现，其中脂氧合酶途径对于脂肪酸分解代谢在苹果中形成酯至关重要。然而，该途径的调节机制仍然难以捉摸。在本研究中，线性回归分析和转基因验证显示脂氧合酶 MdLOX1a 参与酯的生物合成。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 8 个不同苹果品种之间的相关性分析，一种蛋白 MdASG1 （非生物胁迫基因 1） 是 MdLOX1a 和酯产生的正调节因子。MdASG1 在苹果和番茄中过表达刺激脂氧合酶途径并增加脂肪酸衍生的挥发物含量，而后者则因 MdASG1 沉默和 CRISPR/Cas9 敲除而降低。此外，MdASG1 过表达增强了番茄和苹果 “Orin” 愈伤组织的耐盐性，与非胁迫转基因番茄果实相比，脂肪酸衍生的挥发物含量更高。而 MdASG1-Cas9 敲低愈伤组织对盐胁迫无反应，促进脂肪酸衍生挥发物的生物合成。总的来说，这些发现表明 MdASG1 激活 MdLOX1a 表达并参与脂氧合酶途径，随后增加香气化合物的积累，尤其是在中度盐胁迫处理下。结果还为在逆境中提高水果香气质量的理论提供了见解。