Cloning and drought resistance function of BpbZIP36 gene in Betula platyphylla

By cloning the BpbZIP36 gene, constructing a plant expression vector, and obtaining stable transgenic birch plants, this study aimed to investigate the drought resistance function of the BpbZIP36 gene.

Using birch as the experimental material, the BpbZIP36 gene was cloned from birch cDNA as the template. Bioinformatics analysis was performed on the gene, and the pROK2-BpbZIP36 plant expression vector was constructed and introduced into birch seedlings to obtain transgenic birch overexpressing BpbZIP36. The transgenic birch plants and wild-type were subjected to drought stress to study the drought resistance function of the BpbZIP36 gene.

A bZIP gene was obtained from the birch genome database, with an open reading frame (ORF) of 1 269 bp encoding 422 amino acids. The results of multiple sequence alignment showed that the BpbZIP36 protein was similar to the bZIP protein of other plants and a conserved bZIP structural domain. qRT-PCR results showed that the BpbZIP36 gene was expressed in roots, stems, and leaves. In stems and leaves, the expression level of BpbZIP36 peaked at 72 h, while in roots, the highest expression was observed at 24 h of stress treatment, indicating that the BpbZIP36 gene could be induced by drought stress. Physiological index and histochemical staining analyses revealed that under drought stress, the transgenic birch overexpressing BpbZIP36 exhibited lower MDA, H₂O₂ content, and relative electrical conductivity compared to wild-type plants, indicating better cell membrane integrity. The SOD, POD and CAT activities, as well as relative water content, were higher in the transgenic birch. DAB staining showed the lightest coloration in the three overexpression lines, suggesting lower H₂O₂ accumulation and reduced cellular damage. These results demonstrated that the drought resistance capacity of the transgenic birch overexpressing BpbZIP36 was stronger than that of wild-type.

Overexpression of the BpbZIP36 gene enhances the drought resistance capability of transgenic birch.