Abstract
The dehydration responsive element binding (DREB) transcription factors have been reported to be involved in stress responses. Most studies have focused on DREB genes in subgroups A-1 and A-2 in herbaceous plants, but there have been few reports on the functions of DREBs from the A-3–A-6 subgroups and in woody plants. Moreover, mulberry trees are ecologically and economically important perennial woody plants, but there has been little research on its stress physiology, biochemistry and molecular biology. In this study, a DREB gene from the mulberry tree, designated as MnDREB4A, classified into the A-4 subgroup by our previous study, was selected for further characterization. Our results showed that the MnDREB4A protein was localized to the nucleus where it activated transcription. The promoter of MnDREB4A can direct prominent expression downstream of the β-glucuronidase (GUS) gene under heat, cold, drought and salt stress, and GUS staining was deepest after 12 h of stress treatment. The MnDREB4A-overexpression transgenic tobacco showed the improved growth phenotype under untreated conditions, such as greener leaves, longer roots, and lower water loss and senescence rates. Overexpression of MnDREB4A in tobacco can significantly enhance tolerance to heat, cold, drought, and salt stresses in transgenic plants. The leaf discs and seedlings of transgenic plants reduced leaf wilting and senescence rates compared to the wild type plants under the different stress conditions. Further investigation showed that transgenic plants also had higher water contents and proline contents, and lower malondialdehyde contents under untreated condition and stress conditions. Our results indicate that the MnDREB4A protein plays an important role in plant stress tolerance.
Highlights
Abiotic stresses, such as heat, cold, high-salt levels, and drought, present major challenges to sustainable food production because they reduce potential yields by up to 50% in crop plantsPLOS ONE | DOI:10.1371/journal.pone.0145619 December 22, 2015MnDREB4A Improve the Tolerance of Tobacco to Abiotic Stresses [1] developing crops that are better adapted to abiotic stresses is important for food production in many parts of the world
Our previous work suggested that the response to different abiotic stresses by MnDREB4A may be related to the cis-elements in the promoter [39,53]
When exposed to abiotic stresses, the transgenic line had lower leaf wilting and senescence rates than the wild type (WT) plants (Fig 6). These results suggested that overexpression of MnDREB4A gene can improve tolerance to abiotic stresses
Summary
Abiotic stresses, such as heat, cold, high-salt levels, and drought, present major challenges to sustainable food production because they reduce potential yields by up to 50% in crop plantsPLOS ONE | DOI:10.1371/journal.pone.0145619 December 22, 2015MnDREB4A Improve the Tolerance of Tobacco to Abiotic Stresses [1] developing crops that are better adapted to abiotic stresses is important for food production in many parts of the world. Major efforts have been made to enhance stress-tolerance through the use of conventional plant breeding, and generated many crop varieties with improved stress tolerance. In this procedure, the stress resistant genetic variability is identified by screening germplasm collections and selections. Beneficial traits are subsequently introduced into cultivars using complex mating designs [2]. This approach is time-consuming, and labor- and cost-intensive. Contrary to the conventional plant breeding methods, genetic engineering can directly introduce specified genes into plants, which offers the possibility of improving stress tolerance by a more attractive and quick method [4,5]. Transcription factor genes will probably become a powerful tool in the genetic engineering of plant abiotic stress tolerance [17,18]
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