The B‐box transcription factor BnBBX22.A07 enhances salt stress tolerance by indirectly activating BnWRKY33.C03.

Salt stress has a detrimental impact on both plant growth and global crop yields. B‐box proteins have emerged as pivotal players in plant growth and development regulation. Although the precise role of B‐box proteins orchestrating salt stress responses in <italic>B. napus</italic> (<italic>Brassica napus</italic>) is not well understood in the current literature, further research and molecular explorations are required. Here, we isolated the B‐box protein BnBBX22.A07 from <italic>B. napus</italic>. The overexpression of <italic>BnBBX22.A07</italic> significantly improved the salt tolerance of Arabidopsis (<italic>Arabidopsis thaliana</italic>) and <italic>B. napus</italic>. Transcriptomic and histological analysis showed that <italic>BnBBX22.A07</italic> enhanced the salt tolerance of <italic>B. napus</italic> by activating the expression of reactive oxygen species (ROS) scavenging‐related genes and decreasing salt‐induced superoxide anions and hydrogen peroxide. Moreover, BnBBX22.A07 interacted with BnHY5.C09, which specifically bound to and activated the promoter of <italic>BnWRKY33.C03</italic>. The presence of BnBBX22.A07 enhanced the activation of BnHY5.C09 on <italic>BnWRKY33.C03</italic>. Overexpression of <italic>BnHY5.C09</italic> and <italic>BnWRKY33.C03</italic> improved the salt tolerance of Arabidopsis. Functional analyses revealed that BnBBX22.A07‐mediated salt tolerance was partly dependent on <italic>WRKY33</italic>. Taken together, we demonstrate that BnBBX22.A07 functions positively in salt responses not only by activating ROS scavenging‐related genes but also by indirectly activating <italic>BnWRKY33.C03</italic>. Notably, our study offers a promising avenue for the identification of candidate genes that could be harnessed in breeding endeavours to develop salt‐resistant transgenic crops. [ABSTRACT FROM AUTHOR]