Myeloblastosis (MYB) transcription factor (TF) plays a positive role in the growth and stress response of plants; tiowever, information on the functions of MYB repressors in soybean is limited. In the present study, the gene GmMYB3a was identified and characterized as a member of the R2R3 MYB repressor family, which is induced by various abiotic stresses. To understand the functions of GmMYB3a, a trans genic soybean over-expressing GmMYB3a was obtained and the photosynthetic index under salt alkali treatments was evaluated. The transgenic line exhibited a series of negative regulation relative to the wild-type control. Quantitative real tithe polymerase chain reaction revealed that the physiological parameters, including soluble sugar, free proline, and chlorophyll contents; and photosynthetic rate decreased in the transgenic plants. Furthermore, GmMYB3a overexpression down-regulated a set of key genes associated with plant defense signal pathways. These finding suggest that GmMYB3a negatively affects the response of plants to salt stress. (C) 2018 Published by Elsevier Inc.