Abstract
The molecular mechanisms of stress tolerance and the use of modern genetics approaches for the improvement of drought stress tolerance have been major focuses of plant molecular biologists. In the present study, we cloned the Gossypium hirsutum sucrose non-fermenting 1-related protein kinase 2 (GhSnRK2) gene and investigated its functions in transgenic Arabidopsis. We further elucidated the function of this gene in transgenic cotton using virus-induced gene silencing (VIGS) techniques. We hypothesized that GhSnRK2 participates in the stress signaling pathway and elucidated its role in enhancing stress tolerance in plants via various stress-related pathways and stress-responsive genes. We determined that the subcellular localization of the GhSnRK2-green fluorescent protein (GFP) was localized in the nuclei and cytoplasm. In contrast to wild-type plants, transgenic plants overexpressing GhSnRK2 exhibited increased tolerance to drought, cold, abscisic acid and salt stresses, suggesting that GhSnRK2 acts as a positive regulator in response to cold and drought stresses. Plants overexpressing GhSnRK2 displayed evidence of reduced water loss, turgor regulation, elevated relative water content, biomass, and proline accumulation. qRT-PCR analysis of GhSnRK2 expression suggested that this gene may function in diverse tissues. Under normal and stress conditions, the expression levels of stress-inducible genes, such as AtRD29A, AtRD29B, AtP5CS1, AtABI3, AtCBF1, and AtABI5, were increased in the GhSnRK2-overexpressing plants compared to the wild-type plants. GhSnRK2 gene silencing alleviated drought tolerance in cotton plants, indicating that VIGS technique can certainly be used as an effective means to examine gene function by knocking down the expression of distinctly expressed genes. The results of this study suggested that the GhSnRK2 gene, when incorporated into Arabidopsis, functions in positive responses to drought stress and in low temperature tolerance.
Highlights
Plants have developed complex signaling pathways in response to various environmental stresses, such as salt, drought, and cold, and have acquired metabolic functions and developmental methods to survive changing environmental conditions [1]
SnRK2.10 and SnRK2.4 are closely related to GhSnRK2, suggesting that GhSnRK2 belongs to the SnRK2 family (Figure 1A)
The GhSnRK2-green fluorescent protein (GFP) fusion protein driven by the cauliflower mosaic virus (CaMV) 35S promoter was transiently expressed in onion epidermal cells, and the green fluorescent GhSnRK2 protein signals were localized to the nuclei and the cytoplasm, whereas GFP alone was detected throughout the cell (Figure1B). qRT-PCR was performed to quantify the expression level of the GhSnRK2 gene
Summary
Plants have developed complex signaling pathways in response to various environmental stresses, such as salt, drought, and cold, and have acquired metabolic functions and developmental methods to survive changing environmental conditions [1]. As a result, understanding the mechanisms of drought tolerance and developing droughtresistant crop plants have been major targets of plant molecular biologists and biotechnologists. Transgenic approach has reveal many possibilities to improve cold stress in plants by incorporating or deleting genes that regulate a particular characteristic [2]. These approaches provide unique opportunities to improve the genetic quality of plants via the development of particular crop varieties that exhibit enhanced resistance to biotic and cold stresses and improved nutritional quality. Drought limits plant growth due to difficulties in maintaining turgor pressure, photosynthetic decline, osmotic stress-imposed constraints on plant processes and interference with nutrient availability as the soil dries [4]
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