Luo Xian, Luo Ya, Xu Andong, Kong Xiaomei, Wang Xiaoli, Deng Qunxian, Zhang Huifen, Lin Lijin, Jia Yongxia
College of Horticulture, Sichuan Agricultural University, Wenjiang, 611130, PR China.
College of Resources, Sichuan Agricultural University, Wenjiang, 611130, PR China.
BMC Plant Biol. 2025 Aug 6;25(1):1028. doi: 10.1186/s12870-025-07055-y.
Low temperature (LT) restricts the growth and development of pitaya, therefore mitigating these detrimental LT-induced effects is of significant agricultural and economic importance in subtropical regions. This study investigated the effects of exogenous salicylic acid (SA, 2 mM) on the antioxidant system, fatty acid components, degree of unsaturation, and fatty acid desaturases (FADs) gene expression in pitaya seedlings ('Taiwan No. 6') under LT stress. LT stress increased reactive oxygen species (ROS), malondialdehyde (MDA), and relative electrical conductivity (REC), causing visible chilling injury (CI = 0.63). Crucially, LT also elevated saturated fatty acids (C12:0, C16:0, C18:0, C22:0) and decreased unsaturated fatty acids (C16:1, C18:2). This reduced the unsaturation ratio (UFA/SFA) and double bond index (DBI), compromising membrane stability and increasing permeability. However, SA application effectively mitigated these effects. SA improved peroxidase (POD) and catalase (CAT) activities, scavenging ROS and preventing oxidative damage. Crucially, SA upregulated the expression of genes encoding stearoyl-ACP desaturase (SAD) and fatty acid desaturases (FAD) enzymes, such as HuSAD2, HuFAD2, HuFAD4, HuFAD6. Consequently, SA increased unsaturated fatty acid proportions (C16:1, C18:2), UFA/SFA, and DBI. This restored membrane stability and integrity, lowered MDA, REC, and markedly reduced CI (to 0.38). This study demonstrates, for the first time in pitaya, that exogenous SA enhances cold resistance by activating antioxidant systems and regulating HuSADs and HuFADs gene expression to maintain membrane fatty acid unsaturation.
低温（LT）限制了火龙果的生长发育，因此减轻低温诱导的这些有害影响在亚热带地区具有重要的农业和经济意义。本研究调查了外源水杨酸（SA，2 mM）对低温胁迫下火龙果幼苗（‘台湾6号’）抗氧化系统、脂肪酸成分、不饱和度以及脂肪酸去饱和酶（FADs）基因表达的影响。低温胁迫增加了活性氧（ROS）、丙二醛（MDA）和相对电导率（REC），导致可见的冷害（CI = 0.63）。至关重要的是，低温还提高了饱和脂肪酸（C12:0、C16:0、C18:0、C22:0）的含量，降低了不饱和脂肪酸（C16:1、C18:2）的含量。这降低了不饱和度比值（UFA/SFA）和双键指数（DBI），损害了膜稳定性并增加了通透性。然而，施用SA有效地减轻了这些影响。SA提高了过氧化物酶（POD）和过氧化氢酶（CAT）的活性，清除了ROS并防止了氧化损伤。至关重要地，SA上调了编码硬脂酰-ACP去饱和酶（SAD）和脂肪酸去饱和酶（FAD）等酶的基因的表达，如HuSAD2、HuFAD2、HuFAD4、HuFAD6。因此，SA增加了不饱和脂肪酸比例（C16:1、C18:2）、UFA/SFA和DBI。这恢复了膜稳定性和完整性，降低了MDA、REC，并显著降低了CI（降至0.38）。本研究首次在火龙果中证明，外源SA通过激活抗氧化系统和调节HuSADs和HuFADs基因表达以维持膜脂肪酸不饱和度来增强抗寒性。
