拟南芥叶片衰老过程中细胞溶血磷脂和膜脂不饱和度的变化

细胞膜的流动性和渗透性的改变是植物衰老过程中一个内在的、具有破坏性的变化。膜脂组成中，溶血磷脂的出现是膜伤害的一个重要标志；膜脂双键数目的变化是影响膜流动性的主要因素。应用脂类组学的方法，检测了拟南芥野生型及其磷脂酶Dδ (PLDδ)缺失型突变体在离体诱导的、脱落酸（abscisic acid, ABA）和乙烯（ethylene）促进的衰老过程中，溶血磷脂（lysophospholipids, lysoPLs）的分子变化，并通过计算膜脂双键指数（double bond index, DBI）表征了膜流动性的变化。结果表明，在离体诱导的衰老过程和乙烯促进的衰老过程中，溶血磷脂的总含量和各溶血磷脂分子的变化不显著，而在ABA促进的衰老过程中溶血磷脂总含量和部分溶血磷脂分子均显著升高;在上述三种衰老处理下，总膜脂的DBI均下降，但是离体诱导和激素促进的的衰老过程中各类膜脂的DBI的变化却不同。同时我们还发现，抑制PLDδ基因表达降低了ABA促进的衰老过程中溶血磷脂的产生、减缓了ABA和乙烯促进的衰老过程中总的膜脂的DBI的降低。

Changes in Lysophospholipid and Degree of Unsaturated Membrane Lipids are Associated With Senescence in Arabidopsis Leaves

Alterations of membrane fluidity and permeability are an inherent feature of deterioration associated with senescence in plants. With regard to membrane lipid constituents, the occurrence of lysophospholipid (lysoPL) is a signal of membrane damage, while changes in the double bond number of membrane lipids has important effects on membrane fluidity. In the present study, a lipidomics approach was used to study changes in lysoPL molecular species, and, in addition, the double bond index (DBI) of membrane lipids was calculated to indicate membrane fluidity in wild type (WS) and a phospholipid Dδ (PLDδ) knockout mutant of Arabidopsis during detachment induced, abscisic acid (ABA) or ethylene promoted senescence. The results indicated that the content of total lysoPLs and some lysoPL molecular species increased markedly during ABA promoted senescence, while no significant change was detected during detachment induced and ethylene promoted senescence. The DBI of total membrane lipids decreased during three senescence treatments; however, the pattern of change for each membrane lipid class differed between detachment induced and hormone promoted senescence. Suppression of PLDδ attenuated lysoPLs accumulation during ABA promoted senescence, and slowed down the decrease of DBI of the total membrane lipids during ABA and ethylene promoted senescence.