WRKY transcription factors govern selenium metabolism in Broussonetia papyrifera: genome-wide identification, expression profiling, and regulatory network analysis

Broussonetia papyrifera, a novel forage tree species, exhibits a notable ability to accumulate selenium, making it a viable option for selenium enrichment feed. Nevertheless, the molecular mechanisms governing selenium metabolism in this tree are poorly understood, hindering its further development as a selenium accumulator. This study revealed 47 WRKY transcription factors from the B. papyrifera genome. These WRKY transcription factors were characterized by their gene structure, protein domains, and synteny analysis across different species. Based on the phylogenetic analysis, these WRKY genes were categorized into three distinct subfamilies. By integrating transcriptomic and physiological data, nine WRKY genes were strongly correlated with selenium. Subsequently, quantitative qRT-PCR results further confirmed BpWRKY34 and BpWRKY25 as potential regulators of selenium metabolism in B. papyrifera, subcellular localization studies indicated that BpWRKY34 and BpWRKY25 were functional in the cell nucleus. Furthermore, we identified several miRNAs that potentially target WRKY family members. Co-expression network analysis revealed downstream enzymatic networks functionally linked to WRKY transcription factors in the selenium metabolic pathway of B. papyrifera. The integrated analysis of BpWRKY genes identified candidate genes that regulate selenium metabolism, offering a theoretical foundation for developing Se-enriched B. papyrifera through genetic improvement.