Overexpression of transcription factor SlWRKY28 improved the tolerance of Populus davidiana × P. bolleana to alkaline salt stress.

Background: WRKY transcription factors (TFs) have been suggested to play crucial roles in the response to biotic and abiotic stresses. This study is the first to report the alkaline salt regulation of the WRKY gene.

Results: In this study, we cloned a WRKY gene (SlWRKY28) from the Salix linearistipularis and then transferred to the Populus davidiana × P. bolleana for expression. Sequence analysis on the transcriptome of Salix linearistipular showed the significant up-regulation of WRKY gene expression in response to salt-alkali stress in seedlings. Our data showed that SlWRKY28 localized to the nucleus. Furthermore, the expression of the SlWRKY28 from female plants increased with saline-alkali stress according to the northern blot analysis results. The results of 3,3'-Diaminobenzidine (DAB) staining showed that hydrogen peroxide (H₂O₂) concentration was lower under stress, but ascorbate peroxidase (APX) enzyme activity was significantly higher in the overexpressed plants than that in non-transgenic (NT) plants.

Conclusions: We found out the SlWRKY28 induced regulation of the enzyme gene in the reactive oxygen species (ROS) scavenging pathway is a potential mechanism for transgenic lines to improve their resistance to alkaline salt. This study shows theoretical and practical significance in determining SlWRKY28 transcription factors involved in the regulation of alkaline salt tolerance.