Abstract:

Objective: Soil salination is one of the main factors restricting the productivity of agricultural and forestry resources. To adapt to the environment, plants alleviate salt damage by initiating gene expression, altering the physiological metabolism and morphological structure. A growing number of studies have shown that C2H2 zinc finger proteins (ZFPs) play important roles in the regulatory networks of plant response to salt stress. To date, studies on the biological function of plant ZFPs have focused on plant-specific Q-type, while researches on non-Q-type ZFPs is very limited. Previously, 109 genes encoding C2H2 ZFPs, PtrZFPs, were identified from Populus trichocarpa, 62 genes of which encoded the proteins of non-Q-type ZFPs. Identification and analysis of the function of salt-resistant C2H2 zinc finger protein genes will provide important information for further understanding the molecular mechanisms of plants in response to abiotic stress. By analyzing the phenotypes and identifying the functions of transgenic P. davidiana×P. bolleana overexpressing PdbZFP26, this study aims to provide excellent resources and theoretical basis for genetic improvement of salt resistance of P. davidiana×P. bolleana. Method: In this study, real-time quantitative PCR was used to analyze the expression patterns of PdbZFP26 in different organs, and the response to abiotic stresses and phytohormones. The transgenic P. davidiana×P. bolleana was obtained by leaf disc transformation. The growth of transgenic and control lines was observed before and after salt stress treatment, and the physiological indexes of stress resistance were measured to compare the tolerance of different lines to salt stress. Result: Based on the analysis of preliminary expression profile data, a salt stress-inducible C2H2 zinc finger protein gene PdbZFP26 was screened from the stem cDNAs. The coding region of this gene is 2 061 bp, encoding 686 amino acids. PdbZFP26 contained only one C2H2 zinc finger domain and did not have the type-Q characteristic motif "QALGGH". The phylogenetic tree revealed that PdbZFP26 belonged to type-C type ZFPs. The expression pattern analysis showed that PdbZFP26 was specifically expressed in the stem, mainly in xylem (including vascular cambium); In addition to salt stress, both ABA and BRs were able to cause the upregulation of PdbZFP26 to different degrees. The result of the phenotypes showed that the transgenic P. davidiana×P. bolleana overexpressing PdbZFP26 grew significantly better than the control under salt stress, with significantly higher chlorophyll content, lower MDA and H₂O₂ content, and higher antioxidant enzyme activities such as SOD, POD and CAT. Conclusion: The overexpression of PdbZFP26 can reduce peroxide accumulation by increasing activities of antioxidases, and thus improve the tolerance of transgenic P. davidiana×P. bolleana to salt stress.

Key words: P. davidiana×P. bolleana, C2H2 zinc finger protein, salt stress