BnaUBP15s positively regulates seed size and seed weight in Brassica napus

Brassica napus (B. napus) is a globally significant oilseed crop, making a substantial contribution to both human oil and livestock feed production. Enhancing seed weight is crucial for improving rapeseed yield; however, only a limited number of seed weight-related genes have been functionally validated in B. napus thus far. UBIQUITIN-SPECIFIC PROTEASE 15 (UBP15) belongs to the ubiquitin protease pathway and plays a maternal role in prolonging seed development in Arabidopsis. The potential utilization of UBP15 for enhancing seed yield in B. napus has remained unexplored until now. In this study, we identified the orthologs of UBP15 in B. napus and investigated its functionality using the CRISPR-Cas9 system. We generated mutant plants with multiple editing types targeting Bnaubp15s and successfully isolated T-DNA-free homozygous mutant lines that exhibited edits across four homologs of BnaUBP15 in T2 generation plants. Our preliminary data demonstrated that mutation of BnaUBP15s significantly reduced seed size, seed weight, and plant height while noticeably increasing the number of primary branches. These findings not only provide crucial evidence for further elucidating the molecular mechanism underlying the regulation of seed weight and size by BnaUBP15s but also offer promising novel germplasm for enhancing plant architecture.