Genome-wide identification of MYB gene family and exploration of selenium metabolism-related candidates in paper mulberry (Broussonetia papyrifera).

Key message: Genome-wide identified 144 MYB family members in B. papyrifera. Integrated correlation analysis and target gene-binding motif prediction indicate that BpMYB135 is vital in regulating selenium metabolism. Selenium is an essential micronutrient for maintaining the health of humans and animals. Broussonetia papyrifera, a forage tree with high nutritional value, exhibits a remarkable ability to accumulate selenium. Although previous studies have preliminarily unfolded the molecular mechanisms underlying selenium accumulation, the roles of transcription factors in regulating selenium uptake and transformation remain poorly understood. This study used various strategies including bioinformatic, physiological, and molecular experiments to explore candidates regarding Se metabolism. Briefly, 144 MYB transcription factor family members were identified and classified into four types (R1, R2R3, R1R2R3, and R4), with phylogenetic analysis further dividing them into 58 subfamilies. The promoters of those BpMYBs contain numerous cis-acting elements associated with plant growth, development, and stress response. qRT-PCR assay confirmed 8 of 15 BpMYBs exhibit a remarkable correlation with selenium content at the threshold absolute value of 0.5. Additionally, foliar application of exogenous abscisic acid (ABA), methyl jasmonate (MeJA), and salicylic acid (SA) reveals different response patterns of BpMYBs. The subcellular localization assay simultaneously verifies that the candidate BpMYB135 functions within the nucleus. Overall, this funding highlights the potential regulatory mechanisms of selenium metabolism in B. papyrifera, providing a foundation for improving its forage value through genetic modification.