Using high-throughput transcriptome sequence (RNA-Seq) to analyze Nostoc flagelliforme samples under different salt concentrations, we screened sucrose synthase S1 gene from the differentially expressed genes of N. flagelliforme under salt stress. Using the N. flagelliforme genome as a template, we cloned the complete fragment of sucrose synthase S1 gene and analyzed by bioinformatics, and introduced the target gene into Escherichia coli for preliminary expression, so as to further optimize the expression conditions of the target protein. In this study, we cloned the sucrose synthase S1 gene with a fragment size of 2 409 bp successfully by designing specific primers. Bioinformatics analysis showed that the average molecular weight of sucrose synthase S1 protein is 92.85 kDa, which is a hydrophilic protein and highly conserved. Its theoretical isoelectric point is 5.52 and does not contain a transmembrane region. The protein amino acid sequence contains 37 Ser phosphorylation sites, 13 Thr phosphorylation sites, and 8 Tyr phosphorylation sites. Its secondary structure was mainly α-helix and random coil. Purify and recover the target gene amplified in vitro, connect the plasmid pETsumo to construct the expression vector pETsumo-S1, and transform it into E. coli BL21 (DE3) for expression to obtain the foreign protein of the expected size. Optimizing the expression conditions showed that when the OD600 value of the bacterial solution reached 0.8, the final concentration of the inducer IPTG was added at a final concentration of 0.05 mmol/L, then induce the bacterial solution for 6 h under 37 ℃ and 200 r/min ,and the target protein expression reaches the highest. The results enriched the research on the salt stress response genes of N. flagelliforme, laying a foundation for the research of N. flagelliforme gene clusters and gene regulatory loci, and are of great significance for elucidating the regulation mechanism of the salt stress response of N. flagelliforme from the molecular level.
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