Lipidomic insights into the response of Arabidopsis sepals to mild heat

Arabidopsis sepals coordinate flower opening in the morning as ambient temperature rises;however,the underlying molecular mechanisms are poorly understood. Mutation of one heat shock proteinencoding gene, HSP70-16, impaired sepal heat stress responses (HSR), disrupting lipid metabolism,especially sepal cuticular lipids, leading to abnormal flower opening. To further explore, to what extent,lipids play roles in this process, in this study, we compared lipidomic changes in sepals of hsp70-16 andvdac3 (mutant of a voltage-dependent anion channel, VDAC3, an HSP70-16 interactor) grown underboth normal (22 C) and mild heat stress (27 C, mild HS) temperatures. Under normal temperature,neither hsp70-16 nor vdac3 sepals showed significant changes in total lipids;however, vdac3 but nothsp70-16 sepals exhibited significant reductions in the ratios of all detected 11 lipid classes, except themonogalactosyldiacylglycerols (MGDGs). Under mild HS temperature, hsp70-16 but not vdac3 sepalsshowed dramatic reduction in total lipids. In addition, vdac3 sepals exhibited a significant accumulationof plastidic lipids, especially sulfoquinovosyldiacylglycerols (SQDGs) and phosphatidylglycerols (PGs),whereas hsp70-16 sepals had a significant accumulation of triacylglycerols (TAGs) and simultaneousdramatic reductions in SQDGs and phospholipids (PLs), such as phosphatidylcholines (PCs), phosphatidylethanolamines (PEs), and phosphatidylserines (PSs). These findings revealed that the impact ofmild HS on sepal lipidome is influenced by genetic factors, and further, that HSP70-16 and VDAC3differently affect sepal lipidomic responses to mild HS. Our studies provide a lipidomic insight intofunctions of HSP and VDAC proteins in the plant’s HSR, in the context of floral development.

Lipidomic profiling analysis reveals the dynamics of phospholipid molecules in Arabidopsis thaliana seedling growth

High-throughput lipidomic profiling provides a sensitive approach for discovering minor lipid species. By using an advance in electrospray ionization tandem mass spectrome- try, a large set of phospholipid molecular species （126 species） with high resolution were identified from Arabidopsis seedling; of them 31 species are newly identified （16 are unique in plants）, including 13 species of phosphatidic acid （PA）, nine phosphati- dylcholine, six phosphatidylinositol and three phosphatidylser- ine. Further analysis of the lipidomic profile reveals dynamics of phospholipids and distinct species alterations during seedling development. PA molecules are found at the lowest levels in imbibition and follow an increasing trend during seedling growth, while phosphatidylethanolamine （PE） molecules show the opposite pattern with highest levels at imbibition and a general decreasing trend at later stages. Of PA molecular species, 34：2-, 34：3-, 36：4, 36：5-, 38：3- and 38：4-PA increase during radicle emergence, and 34：2- and 34：3-PA reach highest levels during hypocotyl and cotyledon emergence from the seed coat. Conversely, molecular species of PE show higher levels in imbibition and decrease in later stages. These results suggest the crucial roles of specific molecular species and homeostasis of phospholipid molecules in seedling growth and provide insights into the mechanisms of how phospholipid molecules are involved in regulating plant development.

Plasma Lipidomic Subclasses and Risk of Hypertension in Middle-Aged and Elderly Chinese

While disrupted lipid metabolism is a well-established risk factor for hypertension in animal models,the links between various lipidomic signatures and hypertension in human studies remain unclear.We aimed to examine associations between plasma lipidomic profiles and prevalence of hypertension among 2248 community-living Chinese aged 50-70 years.Hypertension was defined according to 2020 International Society of Hypertension global hypertension practice guidelines and 2018 Chinese guidelines.In total,728 plasma lipidomic species were profiled using high-coverage targeted lipidomics.After multivariate adjustment,including lifestyle,body mass index,blood lipids,and sodium intake,110 metabolites from nine lipidomic subclasses showed significant associations with hypertension,among which phosphatidylethanolamines(PEs)had the strongest association.Eleven lipidomic signals for hypertension risk were further identified from the nine subclasses,including PE(18:0/18:2)(OR per SD,1.49;95%confidence intervals,1.30-1.69),phosphatidylcholine(PC)(18:0/18:2)(1.27;1.13-1.43),phosphatidylserine(18:0/18:0)(1.24;1.09-1.41),lysophosphatidylinositol(18:1)(1.17;1.06-1.29),triacylglycerol(52:5)(1.38;1.18-1.61),diacylglycerol(16:0/18:2)(1.42;1.19-1.69),dihydroceramide(24:0)(1.25;1.09-1.43),hydroxyl-sphingomyelins(SM[2OH])C34:1(1.19;1.07-1.33),lysophosphatidylcholine(20:1)(0.86;0.78-0.95),SM(OH)C38:1(0.87;0.79-0.96),and PC(18:2/20:1)(0.84;0.75-0.94).Principal component analysis also showed that a factor mainly containing specific PEs was positively associated with hypertension(1.20;1.09-1.33).Collectively,our study revealed that disturbances in multiple circulating lipidomic subclasses and signatures,especially PEs,were significantly associated with the prevalence of hypertension in middle-aged and elderly Chinese.Future studies are warranted to confirm our findings and determine the mechanisms underlying these associations.