Abstract:The research aimed at finding out the response mechanisms and molecular mechanisms of heat-shock-protein 70 gene under high temperature stress, then analyzing the relationships between Hsp70 gene and thermo-tolerance of leaf lettuce (Lactuca sativa). By homologous cloning and RACE technology, the full-length cDNA of LsHsp70-3701 was obtained. Real-time fluorescence quantitative PCR (qRT-PCR) was used to analyze the expression differences between heat-sensitive variety P-S11 and heat-tolerant variety G-S59 under high temperature. LsHsp70-3701 had a cDNA sequence with 2 191 bp in length, which contains a 1 950 bp open reading flame (ORF) and encodes a deduced 649 amino acids. It has the unique tag sequences of Hsp70 family, and it shares 90% homology with other Hsp70 proteins, such as Arabidopsis thaliana (NP_187864.1), Solanum lycopersicum (NP_001266213.1) and Triticum aestivum (AAB99745.1). The Real-time PCR results showed that the overall expression level of LsHsp70-3701 in the heat resistant variety was significantly higher than that in the heat sensitive variety although it was upregulated in both varieties. The expression in the heat sensitive variety P-S11 was constrained after a period under 42 ℃, while it can maintain a high level for a long time in the heat resistant variety G-S59. These results indicate that LsHsp70-3701 gene may associat with heat resistance in leaf lettuce. It provided data support for solving the problem of Lactuca sativa prone to bolting under high temperature.