外源水杨酸对低温胁迫下黄瓜幼苗根系脂肪酸不饱和度的影响

Effects of Salicylic Acid on Fatty Acid Compositions in the Roots of Cucumber Seedlings Under Low Temperature

为了阐明水杨酸(SA)诱导黄瓜幼苗耐冷性的作用机理,以28℃/18℃(昼/夜)为对照,测定了外源SA对低温胁迫(8℃/8℃)下根系脂肪酸总量、组分、不饱和度以及脂肪酸去饱和酶基因(CsFAD)表达水平的影响。结果表明:低温提高了根系总脂肪酸含量和饱和脂肪酸组分C16︰0、C18︰0的相对含量,并降低了多不饱和脂肪酸C18︰3的比例,根系脂肪酸不饱和度和双键指数降低;而低温下外源施用SA后,脂肪酸组分的变化得到显著缓解,饱和脂肪酸C16︰0的相对含量降低,不饱和脂肪酸C18︰3相对含量升高,脂肪酸不饱和度升高。进一步分析CsFAD的表达水平,发现低温胁迫下,根系CsFAB2.1、CsFAB2.2和CsFAD5表达受到抑制,CsFAD3和CsFAD7的表达升高;施用SA可以解除低温对CsFAB2.1、CsFAB2.2、CsFAB2.3的抑制,CsFAD2.1和CsFAD3的表达也有所升高。低温胁迫下外源施用SA可以诱导黄瓜幼苗根系FAD基因表达,提高脂肪酸不饱和度,提高幼苗耐冷性。

To explore the effects of salicylic acid （SA） on fatty acid compositions in the roots of cucumber （ Cucumis sativus L. ） seedlings under low temperature, the changes in total fatty acid contents and relative content of each composition, as well as expression levels of fatty acid desaturase （CsFAD） genes were detected. The results showed that under low temperature, total fatty acid contents increased in the roots of cucumber seedlings. The relative abundance of major saturated fatty acids （C 16 ： 0 and C 18 ： 0） increased, while the main unsaturated fatty acid （C 18 ： 3 ） decreased upon low temperature stress, and thereby, the unsaturation degree and double bond index of fatty acid were reduced. After exogenous SA of fatty acid was restored. Low temperature could repress the expression of CsFAB2.1, CsFAB2.2 application, total fatty acid content did not show a significant difference. However, the relative abundances of saturated fatty acids were decreased, while the unsaturated fatty acids were elevated, and therefore, the unsaturation degree of fatty acid was restored. Low temperature could repress the expression of CsFAB2.1, CsFAB2.2 and CsFAD5, and induce the expression of CsFAD3 and CsFAD7 in the roots. After SA application, the inhibition of CsFAB2.1, CsFAB2.2 and CsFAB2.3 were released. The expression of CsFAD2.1 was also significantly induced. In summary, under low temperature, exogenous application of SA could induce the expression of CsFAD genes to increase the unsaturation degree of fatty acids, and thereby remain the stability of cell membranes in the roots of cucumber seedlings, and finally increase the cold stress tolerance of seedlings.