Physiological Responses And Transcriptome Analysis Of Lycium Ruthenium Seedlings Under Salt Stress

The Chinese desert shrub Lycium ruthenicum is widely distributed in the arid northwest region with unique salt tolerance mechanism.Its salt tolerance research mainly focuses on the physiological aspect,but there are few reports of molecular mechanisms.In this study,the typical halophytic Lycium ruthenicum as the object,the combination of physiology and transcriptomics methods,the use of technology to deal with the salt concentration of Lycium ruthenicum transcriptome was studied in order to reveal salt tolerance of salt-tolerant plants Mechanism,large-scale planting and salt domestication provided the theoretical basis,the main findings are as follows:1.The net photosynthetic rate（Pn）,chlorophyll,hydrogen peroxide（H₂0₂）,malondialdehyde（MDA）,soluble sugar,soluble protein content and superoxide dismutase（SOD）,Peroxidase（POD）and catalase（CAT）activity were measured under 150 mM NaCl stress.The results show that the contents of chlorophyll a and chlorophyll b in leaves of Lycium ruthenicum seedlings showed a decreasing trend;The content of MDA increased first and then decreased.The activities of SOD,POD and CAT increased first and then decreased.The soluble protein and soluble sugar content increased first and then decreased.In summary,The photosynthetic,antioxidant and osmotic adjustment ability of the Lycium ruthenium seedlings under short-term salt stress increased;thus,reduceing the damage to the cell membrane caused by salt stress and slowing the accumulation of toxic substances are the important reasons for salt tolerance of Lycium ruthenium seedlings.2.The de novo assembly achieved 94,651 unigenes with 55,156 annotated.Amon g them,199 differentially expressed genes（DEGs）were identified between salt-treate d seedlings and control,with 41 up-regulated and 158 down-regulated.These DEGs w ere highly enriched into gene ontology（GO）classifications‘metabolic process’and‘c atalytic activity’,into clusters of orthologous groups（COG）function classifications‘t ranslation,ribosomal structure and biogenesis’and‘energy production and conversion’,and into Kyoto encyclopedia of genes and genomes（KEGG）pathways‘ribosome’a nd‘oxidative phosphorylation’.Significantly,the genes related to ribosome-based bio genesis,oxidative-phosphorylation-based energy metabolism,primary carbon metabol ism including carbon fixation,and primary nitrogen metabolism including arginine an d proline metabolism were predominantly down-regulated;in contrast,protein phosph atase 2C-mediated hormone signal transduction,carotenoid biosynthesis,and lipase-c entered metabolisms including biosynthesis of various membrane lipids were simultan eously up-regulated.The RNA-Seq data were further verified using gene expression p attern analysis of selected DEGs by quantitative real-time polymerase chain reaction（qRT-PCR）.Taken together,these results emphasized the special contribution of carot enoid and lipid metabolisms to the new salinity-adaptive strategies for early vegetativ e seedlings of L.ruthenicum.3.The salt-tolerance gene LrNCED was further studied by brushing.The results showed that salt stress can strongly induce the expression of LrNCED gene and lead to the increase of body ABA content,and the change of ABA content is parallel to the expression level of LrNCED.