biostudies-literatureUnknown16(1)Li BSeed weight is a key component of crop yield. However, molecular mechanisms underlying soybean seed weight variation remain largely elusive. Here, we identify a major seed weight determining gene Glycine max SMALL SEED 6 (GmSMS6) that encodes a 14-3-3 protein. GmSMS6 physically and genetically interacts with the transcription factor GmbZIP151 and the RING-type E3 ligase GmUBQ1. GmSMS6 acts as a regulatory hub switch that coordinates the transcriptional activation activity and GmUBQ1-mediated stability of GmbZIP151, primarily repressing cellular expansion of soybean cotyledons. Knocking out GmSMS6 increases seed weight and protein content but decreases oil accumulation in multiple soybean genetic backgrounds. A loss-of-function allele of GmSMS6 is absent in available soybean resources, whilNature communications10547https://www.ebi.ac.uk/biostudies/studies/S-EPMC12658019biostudies-literatureA 14-3-3 modulator of seed weight and quality for unlocking the yield potential of soybean.PMC12658019He CGu YChen MAn ZLi BZhu WWang YYang CYong BYu HfalseA 14-3-3 modulator of seed weight and quality for unlocking the yield potential of soybean.Seed weight is a key component of crop yield. However, molecular mechanisms underlying soybean seed weight variation remain largely elusive. Here, we identify a major seed weight determining gene Glycine max SMALL SEED 6 (GmSMS6) that encodes a 14-3-3 protein. GmSMS6 physically and genetically interacts with the transcription factor GmbZIP151 and the RING-type E3 ligase GmUBQ1. GmSMS6 acts as a regulatory hub switch that coordinates the transcriptional activation activity and GmUBQ1-mediated stability of GmbZIP151, primarily repressing cellular expansion of soybean cotyledons. Knocking out GmSMS6 increases seed weight and protein content but decreases oil accumulation in multiple soybean genetic backgrounds. A loss-of-function allele of GmSMS6 is absent in available soybean resources, whil2025-01-01T00:00:00Z2025 Nov2026-06-05T21:41:15.071Z2026-05-22T03:15:12.536ZS-EPMC126580194129846310.1038/s41467-025-65598-y