RESUMO
Soybean (Glycine max) production is severely affected in unfavorable environments. Identification of the regulatory factors conferring stress tolerance would facilitate soybean breeding. In this study, through coexpression network analysis of salt-tolerant wild soybeans, together with molecular and genetic approaches, we revealed a previously unidentified function of a class B heat shock factor, HSFB2b, in soybean salt stress response. We showed that HSFB2b improves salt tolerance through the promotion of flavonoid accumulation by activating one subset of flavonoid biosynthesis-related genes and by inhibiting the repressor gene GmNAC2 to release another subset of genes in the flavonoid biosynthesis pathway. Moreover, four promoter haplotypes of HSFB2b were identified from wild and cultivated soybeans. Promoter haplotype II from salt-tolerant wild soybean Y20, with high promoter activity under salt stress, is probably selected for during domestication. Another promoter haplotype, III, from salt-tolerant wild soybean Y55, had the highest promoter activity under salt stress, had a low distribution frequency and may be subjected to the next wave of selection. Together, our results revealed the mechanism of HSFB2b in soybean salt stress tolerance. Its promoter variations were identified, and the haplotype with high activity may be adopted for breeding better soybean cultivars that are adapted to stress conditions.
Assuntos
Domesticação , Flavonoides/biossíntese , Glycine max/fisiologia , Proteínas de Choque Térmico/metabolismo , Proteínas de Plantas/metabolismo , Tolerância ao Sal/fisiologia , Sequência de Bases , Vias Biossintéticas/efeitos dos fármacos , Vias Biossintéticas/genética , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Genes de Plantas , Estudos de Associação Genética , Haplótipos/genética , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/genética , Plantas Geneticamente Modificadas , Regiões Promotoras Genéticas/genética , Ligação Proteica/efeitos dos fármacos , Ligação Proteica/genética , Tolerância ao Sal/efeitos dos fármacos , Cloreto de Sódio/farmacologia , Glycine max/efeitos dos fármacos , Glycine max/genética , Fatores de Transcrição/metabolismo , Transcriptoma/efeitos dos fármacos , Transcriptoma/genética , Regulação para Cima/efeitos dos fármacos , Regulação para Cima/genéticaRESUMO
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.
Assuntos
Arabidopsis/fisiologia , Proteínas de Plantas/metabolismo , Estresse Fisiológico , Fatores de Transcrição/metabolismo , Triticum/genética , Arabidopsis/genética , Clonagem Molecular , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Secas , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Pressão Osmótica , Proteínas de Plantas/genética , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/fisiologia , Regiões Promotoras Genéticas , Cloreto de Sódio/farmacologia , Fatores de Transcrição/genéticaRESUMO
BACKGROUND: Trihelix transcription factors play important roles in light-regulated responses and other developmental processes. However, their functions in abiotic stress response are largely unclear. In this study, we identified two trihelix transcription factor genes GmGT-2A and GmGT-2B from soybean and further characterized their roles in abiotic stress tolerance. FINDINGS: Both genes can be induced by various abiotic stresses, and the encoded proteins were localized in nuclear region. In yeast assay, GmGT-2B but not GmGT-2A exhibits ability of transcriptional activation and dimerization. The N-terminal peptide of 153 residues in GmGT-2B was the minimal activation domain and the middle region between the two trihelices mediated the dimerization of the GmGT-2B. Transactivation activity of the GmGT-2B was also confirmed in plant cells. DNA binding analysis using yeast one-hybrid assay revealed that GmGT-2A could bind to GT-1bx, GT-2bx, mGT-2bx-2 and D1 whereas GmGT-2B could bind to the latter three elements. Overexpression of the GmGT-2A and GmGT-2B improved plant tolerance to salt, freezing and drought stress in transgenic Arabidopsis plants. Moreover, GmGT-2B-transgenic plants had more green seedlings compared to Col-0 under ABA treatment. Many stress-responsive genes were altered in GmGT-2A- and GmGT-2B-transgenic plants. CONCLUSION: These results indicate that GmGT-2A and GmGT-2B confer stress tolerance through regulation of a common set of genes and specific sets of genes. GmGT-2B also affects ABA sensitivity.
