Expression pattern of HTR gene family in desert plant Karelinia caspia and its enhancement of bacterial stress resistance

[Objective] The desert plant Karelinia caspia has a broad-spectrum of stress resistance, including salt/alkali tolerance and high temperature tolerance, which is a precious natural plant germplasm native to Xinjiang. It has been noted that mining the genes involved in extreme temperature and salt tolerance of K . caspia as well as analyzing their expression under stress is critical for using these genes to enhance crop stress resistance, increase yield, and promote the exploration and utilization of the genetic resources of the desert plants. [Methods] Potted K . caspia seedlings were subjected to different durations of high temperature (45 ℃), low temperature (4 ℃), and high salt (400 mmol/L Na+ ) stress. Root, stem, and leaf tissues were collected to analyze the expression of the HTR gene family (KcHTRs) by using RT-PCR and other techniques, and analyze their stress resistance and optimal induction conditions for protein expression by a prokaryotic expression system. [Results] (1) Seven of the KcHTR gene family members were screened and cloned from the transcriptomic data obtained from high temperature treatments of K . caspia. By constructing prokaryotic expression vectors and inducing expression, cDNA lengths of the KCHTR gene family were determined to be between 708 and 789 bp, and the molecular weights of the expressed protein was between 27 and 29 kD. (2) It was found that the optimal expression system of E. coli BL21 was 0.8 at OD600, IPTG concentration 0.5 mmol/L, and induction time 8-10 h at the optimum temperature of 37 ℃. (3) Recombinant E. coli was treated with simulated high temperature, low temperature and salt stress, and the results showed that KcHTRs enhanced the host tolerance to the stresses to certain extent. [Conclusion] The results showed that KcHTRs has broad-spectrum of stress resistance, mainly extreme temperature, and actively responds to stress conditions.