Genome-wide characterization of DUB genes in Betula platyphylla and BpUBP3 function in pollen tube growth.

The ubiquitination/deubiquitination system is a key regulatory mechanism for maintaining proteome homeostasis in eukaryotic cells. Deubiquitinating enzymes (DUBs), which remove ubiquitin from substrate proteins, regulate plant development, stress responses, and other physiological processes. Although DUBs have emerged as important regulators of plant growth and stress responses, their systematic genomic characterization in white birch (Betula platyphylla) remains limited, restricting our understanding of their potential roles in the reproduction of woody plants. In this study, 56 BpDUB genes were identified in white birch (Betula platyphylla) and classified into six conserved subfamilies (UBP, OTU, UCH, MJD, JAMM, and MINDY). Comparative and synteny analyses revealed that DUB genes are evolutionarily conserved while exhibiting lineage-specific divergence across angiosperms. Promoter analysis showed that BpDUBs harbor diverse cis-acting elements associated with growth and development, stress responses, hormone signaling, and transcription factor binding. Treatment with the broad-spectrum DUB inhibitor PR-619 markedly impaired both pollen germination and pollen tube elongation, supporting the involvement of DUB activity in pollen development. RNA-seq analysis showed that BpUBP3 exhibited stage-specific induction during pollen germination, and AS-ODN-mediated downregulation of BpUBP3 reduced pollen germination and pollen tube growth. These findings provide preliminary evidence supporting a role for BpUBP3 in pollen germination and pollen tube growth and provide a basis for further investigation of DUB functions in reproductive development in white birch.