Tissue Succulence And Transcriptome Analysis Of Lycium Ruthenicum Under Salt Stress

Lycium ruthenicum is a salt-dilution halophyte,with typical succulent morphological characteristics in leaf to adapt to the salty environment.The study of the mechanism of the succulence of L.ruthenicum will help to elucidate the salt-tolerance mechanism of halophytes.In this experiment,the tissue culture seedlings of L.ruthenicum were used as experimental materials,they were treated with different concentrations（0 mmol/L-250 mmol/L）of sodium chloride（NaCl）for 4 weeks.The growth state and organ microstructure were observed,the degree of succulence,water retention of the leaves and ion accumulation in various organs were measured of and transcriptome sequencing was analysedby using the Illumina HiSeq^TM2500 Sequencing Platform,which was to study the mechanism of salt stress-induced succulence of L.ruthenicum,providing a theoretical basis for revealing the mechanism of salt tolerance of L.ruthenicum.The main conclusions are as follows:1.After treatment with different concentrations（50 mmol/L,150 mmol/L,250 mmol/L）of Na Cl for 4 weeks,the growth phenotypes of the organs of L.ruthenicum are different:leaf length,root length,and root-shoot ratio increased with the increase of NaCl concentration.The thickness,cross-sectional area of leaf and cross-sectional area of stem also increase,with the cell volume increasing,upper and lower epidermal cells closely arranged,palisade tissue and sponge tissue closely packed.In addition,both leaf water content（TWC）and fresh weight/dry weight ratio（FW/DW）increased with the increase of NaCl stress concentration,and reached the maximum under 250 mmol/L NaCl treatment.The above results showed that a certain concentration of NaCl stress can make the leaves and stems of L.ruthenicum be thicker,and induce the succulence of L.ruthenicum.2.The water loss rate of isolated leaves of plants can reflect the water retention capacity of the leaves.Under NaCl stress,with the increase of stress time,the water loss rate of leaves showed a downward trend,but the decline degree decreased with the increase of NaCl concentration,indicating that a certain concentration of NaCl stress can reduce the water loss rate and increase water retention of the leaf.3.With different concentration of NaCl stress,the concentration of Na⁺and Cl^-ions in different organs increased with different degrees,and the accumulation pattern of ions in organ was leaf>stem>root,indicating that under a certain concentration of salt,L.ruthenicum can absorb the salt ions,as inorganic osmotic solutes,which is one of the reasons for the succulence.The K⁺concentration and K⁺/Na⁺ratio in roots and leaves decreased with the increase of NaCl concentration,but no longer decreased significantly under 250 mmol/L NaCl stress,indicating that under certain concentration of salt stress,L.ruthenicum can maintain homeostasis,which is a adapted to salt habitat performance.4.28.91 Gb clean sequence and 290447 transcripts were obtained by transcriptome sequencing,showed,and 84 of the genes were differentially expressed with significant difference.According to gene function annotation,differently expressed genes（DEG）a gene ontology enrichment analysis indicated that genes related to amino acid transport and metabolism,translation,ribosome structure and biogenesis,protein post-translational modification,protein conversion and chaperone protein,inorganic ion transport and metabolism,transport and synthesis of secondary metabolites were found to be expressed with a significant difference under NaCl treatment.Also,we screen genes related to inorganic ion transport and water transport,involved in succulence,analyzing their expression in mRNA in order to further research on the molecular mechanism of succulence of L.ruthenicum.