The E3 Ligase GmPUB21 Negatively Regulates Drought and Salinity Stress Response in Soybean.

E3-ubiquitin ligases are known to confer abiotic stress responses in plants. In the present study, , a novel U-box E3-ubiquitin ligase-encoding gene, was isolated from soybean and functionally characterized. The expression of , which possesses E3-ubiquitin ligase activity, was found to be significantly up-regulated by drought, salinity, and ABA treatments. The fusion protein GmPUB21-GFP was localized in the cytoplasm, nucleus, and plasma membrane. Transgenic lines of the over-expressing showed more sensitive to osmotic, salinity stress and ABA in seed germination and inhibited mannitol/NaCl-mediated stomatal closure. Moreover, higher reactive oxygen species accumulation was observed in overexpressing plants after drought and salinity treatment than in wild-type (WT) plants. Contrarily, silencing of in soybean plants significantly enhanced the tolerance to drought and salinity stresses. Collectively, our results revealed that negatively regulates the drought and salinity tolerance by increasing the stomatal density and aperture via the ABA signaling pathway. These findings improved our understanding of the role of under drought and salinity stresses in soybean.