Summary: WRKY‐type transcription factors have multiple roles in the plant defence response and developmental processes. Their roles in the abiotic stress response remain obscure. In this study, 64GmWRKYgenes from soybean were identified, and were found to be differentially expressed under abiotic stresses. Nine GmWRKY proteins were tested for their transcription activation in the yeast assay system, and five showed such ability. In a DNA‐binding assay, three proteins (GmWRKY13, GmWRKY27 and GmWRKY54) with a conserved WRKYGQK sequence in their DNA‐binding domain could bind to the W‐box (TTGAC). However, GmWRKY6 and GmWRKY21, with an altered sequence WRKYGKK, lost the ability to bind to the W‐box. The function of three stress‐induced genes,GmWRKY13,GmWRKY21andGmWRKY54, was further investigated using a transgenic approach.GmWRKY21‐transgenicArabidopsisplants were tolerant to cold stress, whereasGmWRKY54conferred salt and drought tolerance, possibly through the regulation ofDREB2AandSTZ/Zat10. Transgenic plants over‐expressingGmWRKY13showed increased sensitivity to salt and mannitol stress, but decreased sensitivity to abscisic acid, when compared with wild‐type plants. In addition,GmWRKY13‐transgenic plants showed an increase in lateral roots. These results indicate that the threeGmWRKYgenes play differential roles in abiotic stress tolerance, and thatGmWRKY13may function in both lateral root development and the abiotic stress response.

Summary: NAC transcription factors play important roles in plant growth, development and stress responses. Previously, we identified multiple NAC genes in soybean (Glycine max). Here, we identify the roles of two genes, GmNAC11 and GmNAC20, in stress responses and other processes. The two genes were differentially induced by multiple abiotic stresses and plant hormones, and their transcripts were abundant in roots and cotyledons. Both genes encoded proteins that localized to the nucleus and bound to the core DNA sequence CGT[G/A]. In the protoplast assay system, GmNAC11 acts as a transcriptional activator, whereas GmNAC20 functions as a mild repressor; however, the C‐terminal end of GmANC20 has transcriptional activation activity. Over‐expression of GmNAC20 enhances salt and freezing tolerance in transgenic Arabidopsis plants; however, GmNAC11 over‐expression only improves salt tolerance. Over‐expression of GmNAC20 also promotes lateral root formation. GmNAC20 may regulate stress tolerance through activation of the DREB/CBF–COR pathway, and may control lateral root development by altering auxin signaling‐related genes. GmNAC11 probably regulates DREB1A and other stress‐related genes. The roles of the two GmNAC genes in stress tolerance were further analyzed in soybean transgenic hairy roots. These results provide a basis for genetic manipulation to improve the agronomic traits of important crops.

WRKY‐type transcription factors are involved in multiple aspects of plant growth, development and stress response. WRKY genes have been found to be responsive to abiotic stresses; however, their roles in abiotic stress tolerance are largely unknown especially in crops. Here, we identified stress‐responsive WRKY genes from wheat (Triticum aestivum L.) and studied their functions in stress tolerance. Forty‐three putative TaWRKY genes were identified and two multiple stress‐induced genes, TaWRKY2 and TaWRKY19, were further characterized. TaWRKY2 and TaWRKY19 are nuclear proteins, and displayed specific binding to typical cis‐element W box. Transgenic Arabidopsis plants overexpressing TaWRKY2 exhibited salt and drought tolerance compared with controls. Overexpression of TaWRKY19 conferred tolerance to salt, drought and freezing stresses in transgenic plants. TaWRKY2 enhanced expressions of STZ and RD29B, and bound to their promoters. TaWRKY19 activated expressions of DREB2A, RD29A, RD29B and Cor6.6, and bound to DREB2A and Cor6.6 promoters. The two TaWRKY proteins may regulate the downstream genes through direct binding to the gene promoter or via indirect mechanism. Manipulation of TaWRKY2 and TaWRKY19 in wheat or other crops should improve their performance under various abiotic stress conditions.

Summary: Soybean is one of the most important leguminous seed crops among the oil crops. Although the pathways for lipid biosynthesis have been identified, the factors that regulate the biosynthetic pathways at the transcriptional level are largely unknown. Here, we report our findings on the involvement of soybean Dof‐type transcription factor genes in the regulation of the lipid content in soybean seeds. We identified 28 Dof‐type transcription factor genes in soybean plants, and these genes displayed diverse patterns of expression in various organs. Seven flower/pod‐specific genes and one constitutively expressed gene were further investigated. The proteins encoded by these seven genes were localized in the nucleus, and exhibited different abilities for transcriptional activation and DNA binding. Two genes, GmDof4 and GmDof11, were found to increase the content of total fatty acids and lipids in GmDof4 and GmDof11 transgenic Arabidopsis seeds. We also found that the 1000‐seed weight was increased in the GmDof4 and GmDof11 transgenic plants. Using microarray and DNA binding analysis, we found that the two Dof‐like proteins, GmDof4 and GmDof11, activated the acetyl CoA carboxylase gene and long‐chain‐acyl CoA synthetase gene, respectively, by direct binding to the cis‐DNA elements in their promoter regions. In addition, both proteins downregulated the storage protein gene, CRA1, through direct binding. These results suggest that the two GmDof genes may augment the lipid content of soybean seeds by upregulating genes that are associated with the biosynthesis of fatty acids.