The aerial parts of apple are protected against environmental stress by cuticular wax. Although it has been suggested that several long-chain acyl-CoA synthetases are involved in wax biosynthesis, the molecular pathway of apple cuticular wax biosynthesis remains unclear. In this study, an MdLACS4 protein with long-chain acyl-CoA synthetase activity was isolated from apple. The MdLACS4 gene was highly expressed in pericarp, stem, and mature leaf tissues. Ectopic expression of MdLACS4 in Arabidopsis induced early flowering. Compared with wild-type plants, MdLACS4 transgenic Arabidopsis exhibited lower water loss rates, reduced epidermal permeability, increased cuticular wax in stems and leaves, and altered cuticular ultrastructure. Furthermore, the accumulation of cuticular wax enhanced the resistance of MdLACS4 transgenic plants to drought and salt stress. Finally, predicted protein functional interaction networks for LACS4 suggested that the molecular regulation pathway of MdLACS4 mediates wax biosynthesis in apple.

中文翻译：

---

苹果长链酰基辅酶A合成酶MdLACS4诱导拟南芥早期开花并增强非生物胁迫抗性

苹果的地上部分通过表皮蜡保护免受环境压力。尽管已经提出几种长链酰基辅酶A合成酶参与蜡生物合成，但苹果表皮蜡生物合成的分子途径仍不清楚。本研究从苹果中分离出一种具有长链酰基辅酶A合成酶活性的MdLACS4蛋白。MdLACS4 基因在果皮、茎和成熟叶组织中高表达。MdLACS4 在拟南芥中的异位表达诱导早花。与野生型植物相比，MdLACS4 转基因拟南芥表现出更低的失水率、降低的表皮渗透性、增加茎和叶中的角质层蜡质以及改变的角质层超微结构。此外，表皮蜡的积累增强了 MdLACS4 转基因植物对干旱和盐胁迫的抗性。最后，预测的 LACS4 蛋白质功能相互作用网络表明 MdLACS4 的分子调控途径介导了苹果的蜡生物合成。