Birch (Betula platyphylla) BES/BZR transcription factor BpBZR1-6 improves salt tolerance in transgenic Arabidopsis thaliana.

Background: Salt stress is one of the major environmental factors affecting plant growth and productivity. BRI1-EMS suppressor 1/brassinazole-resistant 1 ((BES1/BZR1) plays an important role in responding to abiotic stress in plants. Although the impacts of BES1/BZR1 on plant growth and resistance have been documented, the potential mechanisms are not fully elucidated in Betula platyphylla. This work contributes to the understanding of how BES1/BZR1 promotes stress tolerance in woody plants.
Results: Six BES1/BZR1 family members were identified from Betula platyphylla. Cis-element analysis showed that the promoters of six genes were rich in ABA-responsive element (ABRE), MYB and MBS cis-acting elements, which are reported to be involved in abiotic stress responses. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis indicated that BpBZR1-6 (BPChr10G06000) could be induced by salt stress, ABA and BRs. BpBZR1-6 was localized in the nucleus and had transactivation activity. Ectopic expression of BpBZR1-6 enhanced Arabidopsis tolerance and decreased abscisic acid (ABA) sensitivity under salt treatment. Specifically, the seed germination rate, root length, fresh weight and chlorophyll content were significantly higher in BpBZR1-6-overexpressing (OE) transgenic plants than in wild-type (WT) plants after salt stress (P < 0.05). Additionally, BpBZR1-6 overexpression showed enhanced the reactive oxygen species (ROS) scavenging capability under salt stress, including increasing the activities of antioxidant enzyme, resulting in a decrease in O ₂ ^- and H ₂ O ₂ accumulation, and reducing malondialdehyde (MDA) content. Meanwhile, the expression levels of six antioxidant enzyme genes were higher in OE plants than in WT plants after stress.
Conclusion: BpBZR1-6 overexpression enhanced the salt tolerance of transgenic plants by modulating antioxidant enzyme gene expression and ROS scavenging, which may provide underlying strategy for breeding of salt-tolerant plants.
Competing Interests: Declarations. Ethics approval and consent to participate: Birch (Betula Platyphylla) and Poplar (Populus trichocarpa) specimens were obtained from Northeast Forestry University, Harbin, China. The voucher specimens were stored in Northeast Forestry University. The plants were identified by Yao Chi. All plant materials used in this study were owned by the authors and/or no permissions are required. All the plants complied with national guidelines and legislation, and did not deposit in a public available herbarium and involve in any endangered or protected species. Consent for publication: Not applicable. Competing interests: The authors declare no competing interests.
(© 2024. The Author(s).)