Identification of Sulfate Transporter Genes in Broussonetia papyrifera and Analysis of Their Functions in Regulating Selenium Metabolism

<i>Broussonetia papyrifera</i> has strong adaptability and exhibits a strong ability to accumulate selenium. Its leaves are rich in crude protein, amino acids, and minerals, making them high-quality feed materials. To improve the selenium-enriched ability of <i>B. papyrifera</i> and promote the development of selenium-enriched agricultural products, we screened and identified the sulfate transporters associated with selenium absorption in <i>B. papyrifera</i>. By treating the leaves of <i>B. papyrifera</i> with different concentrations of sodium selenate and analyzing the correlation between gene expression and selenium content, we identified <i>BpSULTR3;1</i> and <i>BpSULTR3;4</i>, which may be involved in selenium absorption and transport in <i>B. papyrifera</i>. We further validated the functions of <i>BpSULTR3;1</i> and <i>BpSULTR3;4</i> through transgenic experiments in <i>Arabidopsis thaliana</i>. The results showed that overexpressing <i>BpSULTR3;1</i> significantly increased the total selenium content in <i>A. thaliana</i>, up to 2.31 times, and also increased the contents of three forms of organic selenium (SeCys₂, MeSeCys and SeMet) in transgenic <i>A. thaliana</i>. These findings provide solid theoretical support for improving <i>B. papyrifera</i>'s selenium enrichment ability through genetic improvement.