Soybean Trihelix Transcription Factors GmGT-2A and GmGT-2B Improve Plant Tolerance to Abiotic Stresses in Transgenic Arabidopsis

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

ABA signaling inhibits oxalate-induced production of reactive oxygen species and protects against Sclerotinia sclerotiorum in Arabidopsis thaliana

Oxalic acid is an essential virulence factor of Sclerotinia sclerotiorum that elicits wilting symptoms in infected host plants. Foliar wilting in response to oxalic acid is known to be dependent on an increase in stomatal conductance. To determine whether stomatal regulation controls susceptibility to S. sclerotiorum, abscisic acid-insensitive and open stomata mutants of Arabidopsis thaliana were analyzed. Whereas abscisic acid-insensitive mutants were hypersusceptible to S. sclerotiorum, open stomata mutants were as susceptible as wild type. It was concluded that stomatal regulation does not control susceptibility to S. sclerotiorum because open stomata mutants are known to only impair guard cells whereas abscisic acid-insensitive mutants also affect other cell types. Guard cell-independent processes also control sensitivity to oxalic acid because oxalic acid was more toxic to abscisic acid-insensitive mutants than to open stomata mutants. To explore a possible mechanism of toxicity, production of reactive oxygen species was measured in plant cells after exposure to oxalic acid. Oxalic acid was found to elicit reactive oxygen species production independently of abscisic acid. Nevertheless, cancellation of reactive oxygen species elicitation after co-stimulation of wild-type guard cells with oxalic acid and abscisic acid provided evidence for antagonistic interaction between both molecules.Peer reviewe