Genome-wide identification of GRF transcription factors in soybean and expression analysis of GmGRF family under shade stress.

Background: The Growth-regulating factor (GRF) family encodes plant-specific transcription factors which contain two conserved domains, QLQ and WRC. Members of this family play vital roles in plant development and stress response processes. Although GRFs have been identified in various plant species, we still know little about the GRF family in soybean (Glycine max).

Results: In the present study, 22 GmGRFs distributed on 14 chromosomes and one scaffold were identified by searching soybean genome database and were clustered into five subgroups according to their phylogenetic relationships. GmGRFs belonging to the same subgroup shared a similar motif composition and gene structure. Synteny analysis revealed that large-scale duplications played key roles in the expansion of the GmGRF family. Tissue-specific expression data showed that GmGRFs were strongly expressed in growing tissues, including the shoot apical meristems, developing seeds and flowers, indicating that GmGRFs play critical roles in plant growth and development. On the basis of expression analysis of GmGRFs under shade conditions, we found that all GmGRFs responded to shade stress. Most GmGRFs were down-regulated in soybean leaves after shade treatment.

Conclusions: Taken together, this research systematically analyzed the characterization of the GmGRF family and its primary roles in soybean development and shade stress response. Further studies of the function of the GmGRFs in the growth, development and stress tolerance of soybean, especially under shade stress, will be valuable.