Involvement Of Lipid Metabolites In The Response Of Sweet Potato (Ipomeoa Batatas(L).Lam) To Salt Stress

Salinity stress inhibits the growth and development of crops and impacts the agriculture production to a great extent.Sweet potato(Ipomoea batatas(L.)Lam.)is dicotyledonous plant that belongs to the family Convolvulaceae.Sweet potato is important food and industrial crop that ranks seventh in terms of worldwide staple food production(ranks fourth in China).However,the mechanisms of salinity tolerance in sweet potato is not clear and still needs further investigation.Lipid remodeling plays important role in the adaptation of plants to the environmental stresses,while the roles of lipid remodeling and lipid metabolites in the mediation of plant salt tolerance are still unclear.Therefore,further study the lipid metabolism process in sweet potato with different salinity tolerance may contributes to the understanding of salinity tolerance in different sweet potato cultivars.In this dissertation,we investigated the alterations of lipidome in the root and leaf tissues of salinity-stressed Xu 22 and Xu 32,which are two elite sweet potato cultivars with different salt tolerance,by using of non-targeted lipidomics method based on the UPLC/ESI-QTOF-MS.In addition,we also investigated the roles of specific lipid metabolites in the mediation of salinity responses by using of exogenous supplied and pharmacological methods.The results are listed as follows:(1)The effect of salinity stress on the lipid metabolism in sweet potato:PCA analysis based on our lipidome data showed that salinity treatment led to remodeling of the leaf and root lipidome in both cultivars,by predominantly inducing the decrease of phosphatidic acid(PA),phosphatidyl ethanolamine(PE),phosphatidylcholine(PC),phosphatidylinositol(PI),phosphatidylglycerol(PG),diacylglycerol(DG),monogalactosyldiaclyglycerol(MGDG)and sphingolipids.Salinized Xu 22(salt tolerant)leaves generally maintained higher abundance of most of these lipid species than that of Xu32(salt sensitive).However,no obvious difference was observed in roots between the two cultivars.Interestingly,salinity stress caused a significant increase of phosphatidylserine(PS)abundance in Xu 22 leaves,by predominantly triggering the increase of PS(20:5/22:6)molecular species.Xu 32 lacked this response.Furthermore,Xu 32 leaves accumulated higher triacylglycerol(TG)level than that of Xu 22 under salinity condition.q RT-PCR data showed that the gene encode PS synthetase(PSS1)in the leaves of Xu 22 was upregulated upon the salinity stress and the gene encode TG-specific lipase(SDP1)in the roots of Xu22was also upregulated by salinity stress.(2)The effect of exogenous PS on the salinity tolerance in Xu 32:In our detached leaf experiments,an obvious phenomenon was observed that exogenous PS(derived from plant or animal)delayed the salt-induced leaf senescence in Xu 32.The better effect was seen in Plant-derived PS.Several physiological indexes were altered in the presence of PS in salinized Xu 32 leaves.These changes included the enhancement of chlorophyll content,the decreased MDA content and ROS accumulation.Exogenous application of PS delayed the salt-induced leaf senescence in Xu 32 via reduction of salt-induced K~+efflux and upregulation of plasma membrane(PM)H~+-ATPase activity.(3)The effect of DMP on the salinity tolerance in the detached leaves of Xu 22:In this experiment,DMP,which is an inhibitor of TG mobilization in plants,was applied.DMP treatment altered physiological responses in salinized Xu 22 leaves.These changes included the decreased chlorophyll content,the increased MDA content and ROS accumulation,the impaired K~+/Na~+homeostasis and the lowed ATP content.In addition,the PM H~+-ATPase activity was also reduced in the presence of DMP in salinized Xu 22 leaves.These data indicated that TG may plays an important role in the energy turnover in salinized sweet potato.Taken together,our results revealed the detail changes of lipid metabolism in different sweet potato cultivars under salinity condition.We also discovered the important roles of PS and TG in the mediation of salt tolerance in sweet potato.Our investigation supplies abundant data to understanding the physiological and molecular mechanisms of salt tolerance in sweet potato cultivars and also supplies theoretical basis for the breeding of salt-tolerant sweet potato cultivars in the future.