Analysis Of Polylipid Changes In Arabidopsis Thaliana And Salina Mustard Under Drought And Salt Stress

Thellungiella salsuginea is closely related to Arabidopsis thaliana,but they have obvious differences in adapting to drought and salt stress.Lipid polymers,including cutin and suberin,play an important role in the defense of plants against external stresses.In this thesis,we comparatively studied lipid polymers metabolism and expression of related genes in leaves and roots of A.thaliana and T.salsuginea under salt and drought stress.The difference in leaf epidermal permeability of the two plants under drought and salt stress were measured.The results showed that their epidermal permeability was decreased with increasing stress intensity.Fourteen kinds of cutin monomers were identified from the leaves of the two species by GC-MS,which were assigned into three classes:unsubstituted fatty acids,fatty diacids and hydroxy fatty acids in fatty acids.Including three kinds of components,namely C18:3?C18:2 and C18:2 dioic.The total amount of cutin monomers in the leaves of the two species under salt stress were both decreased,while the decline in T.salsuginea was in higher degree than that in A.thaliana.Under two consecutive drought stresses,the total amount of cutin monomers in the leaves of A.thaliana were always increased,while that was firstly increased and then decreased in T.salsuginea.Nineteen kinds of suberin monomers were identified from the root epidermis of both two species.After salt stress,there are three kinds of components in A.thaliana with relative content exceeding 10%,namely C18:2,C18:3 and 18-OH C18:1,while there are 6 kinds in T.salsuginea,namely C18:2?C18:3?C18:1 dioic?and 18-OH C18:1.Similar to cutin monomers,the suberin monomers also belong to three types of fatty acids such as unsubstituted fatty acids,fatty diacids and hydroxy fatty acids.The total amount of suberin monomers in the roots of A.thaliana showed a downward trend under low or high salt stress;while it did not change significantly under low salt stress,but increased under high salt stress in T.salsuginea.Under two consecutive drought stresses,the total amount of suberin monomers in the roots of A.thaliana did not change significantly at first,but then increased significantly;while in T.salsuginea,it showed a continuous increasing trend.The expression of lipid polymers metabolism-related genes in A.thaliana and T.salsuginea under salt and drought stress were detected by qRT-PCR.The results of showed that the number of up-regulated and down-regulated genes in A.thaliana leaves under salt stress were equivalent,while almost all genes in T.salsuginea leaves were down-regulated under high-salt stress.Under deep drought stress,most of the genes in A.thaliana leaves were up-regulated,but it showed the opposite trend in leaves of T.salsuginea.Under salt stress,most genes were up-regulated in roots of A.thaliana.Under deep drought stress,most genes were up-regulated in roots of both A.thaliana and T.salsuginea.In summary,A.thaliana and T.salsuginea had similarities and differences in the changes of leaves cutin and roots suberin monomers under salt and drought stress.The changes of genes expression showed a certain correlation with the changes in lipid polymer metabolism.In this study,the research was conducted about the metabolic changes of lipid polymers in the leaves and roots of A.thaliana and T.salsuginea under salt and drought stress,including the chemical compositions and the expression of metabolism-related genes in lipid polymers,by chemical and molecular biological methods.Our study provides an important basis for role of the lipid polymers in response to water stress and helps reveal plant resistance mechanisms.