Drought Stress Tolerance In Tobacco Research Articles

Heterologous expression of the peach sucrose transporter (PpSUT2) in increased cold and drought stress tolerance in tobacco

ABSTRACT Peach is an important fruit tree worldwide. Sucrose transporters (SUTs) have been extensively studied in relation to plant growth, development, and stress responses. In this study, we cloned a putative SUT, PpSUT2, from the peach cultivar ‘New Kawanakajima.’ Bioinformatics analysis predicted that the protein had functional domains typical of the GPH_sucrose family. Phylogenetic analysis revealed high sequence similarity between PpSUT2 and SUTs from other plant species. The qRT-PCR suggested that PpSUT2 was expressed concurrently in the petals, sepals, pistils, stamen, phloem, and leaves. Different trends and different relative expression levels were observed during the flowering and fruit development periods. Western blot analysis produced similar results. The heterologous expression of SUTs in the defective yeast SUSY7/ura3 showed that PpSUT2 had a complementary function on SD sucrose medium. This indicated that it had sucrose transport activity and might be a signal protein. Then, 11PpSUT2 transgenic tobacco plants were obtained.After exposure to low temperature and drought stress conditions, the transgenic overexpression plants exhibited increased proline and soluble sugar content, reduced malondialdehyde (MDA) content and reduced relative conductivity, and less membrane injury. These results suggest that the overexpression of PpSUT2 in tobacco promoted greater resistance to cold and drought.

Anthocyanins are Key Regulators of Drought Stress Tolerance in Tobacco.

Simple SummaryWater scarcity is one of the main threats for the future of agriculture and the worldwide population. Improving the ability of crop species to grow and survive with less water is therefore essential. A fundamental goal of most scientists working in this area is to understand the mechanisms plants must potentiate to better survive under reduced water availability. Here we provide evidence that accumulation of anthocyanins, a major player in red leaf color, may fulfil two important functions. First, they serve as a filter for protecting plants against excessive sunlight; second, they control plant water loss by reducing stomatal transpiration and density. Since excessive sunlight and temperature, associated with climate change, come along with water shortage, these pigments may protect and help plants to survive throughout hot and dry seasons. Our results have important social implications for people living in areas where rising temperatures and water shortages are already critical. Breeding programs to obtain crops with these stress tolerance traits can be specifically designed for these environments.Abiotic stresses will be one of the major challenges for worldwide food supply in the near future. Therefore, it is important to understand the physiological mechanisms that mediate plant responses to abiotic stresses. When subjected to UV, salinity or drought stress, plants accumulate specialized metabolites that are often correlated with their ability to cope with the stress. Among them, anthocyanins are the most studied intermediates of the phenylpropanoid pathway. However, their role in plant response to abiotic stresses is still under discussion. To better understand the effects of anthocyanins on plant physiology and morphogenesis, and their implications on drought stress tolerance, we used transgenic tobacco plants (AN1), which over-accumulated anthocyanins in all tissues. AN1 plants showed an altered phenotype in terms of leaf gas exchanges, leaf morphology, anatomy and metabolic profile, which conferred them with a higher drought tolerance compared to the wild-type plants. These results provide important insights for understanding the functional reason for anthocyanin accumulation in plants under stress.

Physiological and Transcriptome Profiling Analyses Reveal Important Roles of Coronatine in Improving Drought Tolerance of Tobacco

Coronatine (COR) is a phytotoxin produced by Pseudomonas syringae and is a functional analogue of the bioactive hormone JA-Ile, which is widely involved in plant defence responses. In this study, we explored the effects of exogenous applications of COR on tobacco plants under polyethylene glycol-induced drought stress. Compared with control (CK), COR-treated tobacco plants exhibited higher leaf relative water content and better photosynthetic performance under drought exposure. Ultrastructural examination revealed that drought led to stomatal closure and disorganization of granum stacking in the chloroplasts (with obvious accumulation of plastoglobuli), and mitochondria in the CK samples presented injured cristae. In the leaf tissue of the COR-treated plants, regularly stacked granum thylakoids, few plastoglobuli and intact mitochondrial membranes and cristae were observed. Totals of 1803 and 6207 differentially expressed genes (DEGs) were identified between the samples from the COR-treated and CK plants under well-watered and drought conditions. Functional annotation analysis revealed that these DEGs were involved mainly in plant hormone signal transduction, cellular carbohydrate metabolic processes and photosynthesis processes. Six hundred forty transcription factor genes were also identified among the DEGs. This study provides a global view of COR-induced drought stress tolerance in tobacco from both physiological and transcriptional aspects.

SlCOR413IM1: A novel cold-regulation gene from tomato, enhances drought stress tolerance in tobacco

Drought stress adversely affects plant growth, development, and productivity. Genes functioning in plant response to drought stress are essential for drought tolerance. In this study, SlCOR413IM1, a cold-regulated gene isolated from Solanum lycopersium, was transferred to Nicotiana tabacum to investigate its function under drought stress. The subcellular localisation of SlCOR413IM1-GFP fusion protein in Arabidopsis protoplasts suggested that SlCOR413IM1 is a chloroplast protein. Expression analyses revealed that SlCOR413IM1 responded to drought and cold stresses. Under drought stress, transgenic plants maintained the high maximum photochemical efficiency, net photosynthetic rate (Pn) and D1 protein content of photosystem II (PSII). Compared with wild-type (WT) plants, transgenic plants showed higher superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities and proline and soluble sugar content, which reduced reactive oxygen species (ROS) generation. However, the high SOD and APX activities in transgenic plants were independent of their transcription levels. Moreover, the transgenic plants exhibited better seed germination, water status and survival, as well as lower malondialdehyde (MDA) content and relative electrical conductivity (REC) than WT plants under drought stress. Taken together, these data demonstrated that overexpression of SlCOR413IM1 enhanced drought stress tolerance in transgenic tobacco.

Overexpression of the Maize psbA Gene Enhances Drought Tolerance Through Regulating Antioxidant System, Photosynthetic Capability, and Stress Defense Gene Expression in Tobacco.

The psbA (encoding D1 protein) plays an important role in protecting photosystem II (PSII) from oxidative damage in higher plants. In our previous study, the role of the psbA from maize (Zea mays. L) in response to SO2 stress was characterized. To date, information about the involvement of the psbA gene in drought response is scarce. Here we found that overexpression (OE) of ZmpsbA showed increased D1 protein abundance and enhanced drought stress tolerance in tobacco. The drought-tolerant phenotypes of the OE lines were accompanied by increases of key antioxidant enzymes SOD, CAT, and POD activities, but decreases of hydrogen peroxide, malondialdehyde, and ion leakage. Further investigation showed that the OE plants had much less reductions than the wild-type in the net photosynthesis rate (Pn), stomatal conductance (Gs), and the maximal photochemical efficiency of PSII (Fv/Fm) during drought stress; indicating that OE of ZmpsbA may alleviate photosynthesis inhibition during drought. qRT-PCR analysis revealed that there was significantly increased expression of NtLEA5, NtERD10C, NtAREB, and NtCDPK2 in ZmpsbA-OE lines. Together, our results indicate that ZmpsbA improves drought tolerance in tobacco possibly by alleviating photosynthesis reduction, reducing reactive oxygen species accumulation and membrane damage, and modulating stress defense gene expression. ZmpsbA could be exploited for engineering drought-tolerant plants in molecular breeding of crops.

Grafting improves drought tolerance by regulating antioxidant enzyme activities and stress-responsive gene expression in tobacco

Grafting has been used to induce abiotic stress tolerance in horticultural crops recently. However, few studies have come out with the effects of grafting and its possible molecular mechanism under drought conditions in tobacco. In this study, using the drought-tolerant cultivar Nongda202 as a rootstock and the drought-sensitive cultivar K326 as a scion, we exposed non-grafted (K326/K326), self-grafted (K326/K326) and rootstock-grafted (K326/Nongda202) tobacco plants to drought stress over a 12-day period, and investigated their differential physiological and molecular responses to drought stress. Our results showed that drought-induced inhibition of growth was significantly alleviated in rootstock-grafted plants, as was evidenced by the physiological indexes, such as much higher SOD and CAT activities, higher levels of proline accumulation and lower levels of lipid peroxidation. Further expression analysis by real-time PCR indicated that rootstock-grafting affected transcripts of stress-responsive genes NtAREB, NtCDPK2, NtLEA5 and NtERD10C in a prompt and lasting manner. Together, these results demonstrated that grafting with rootstock genotypes tolerant to drought could improve drought stress tolerance in tobacco by regulating antioxidant enzyme activities and stress-responsive gene expression. This study will facilitate to broaden our understanding of the regulatory machinery of grafting, and will accelerate potential application of the grafting technique in improving biotic and abiotic stress tolerance in crop plants.

OsACA6, a P‐type IIB Ca2+ATPase promotes salinity and drought stress tolerance in tobacco by ROS scavenging and enhancing the expression of stress‐responsive genes

Calcium (Ca²⁺) regulates several signalling pathways involved in growth, development and stress tolerance. Cellular Ca²⁺ homeostasis is achieved by the combined action of channels, pumps and antiporters, but direct evidence for a role of Ca²⁺ATPase pumps in stress tolerance is lacking. Here we report the characterization of a Ca²⁺ ATPase gene (OsACA6) from Oryza sativa, and elucidate its functions in stress tolerance. OsACA6 transcript levels are enhanced in response to salt, drought, abscisic acid and heat. In vivo localization identified plasma membranes as an integration site for the OsACA6-GFP fusion protein. Using transgenic tobacco lines, we demonstrate that over-expression of OsACA6 is triggered during salinity and drought stresses. The enhanced tolerance to these stresses was confirmed by changes in several physiological indices, including water loss rate, photosynthetic efficiency, cell membrane stability, germination, survival rate, malondialdehyde content, electrolyte leakage and increased proline accumulation. Furthermore, over-expressing lines also showed higher leaf chlorophyll and reduced accumulation of H₂O₂ and Na⁺ ions compared to the wild-type. Reduced accumulation of reactive oxygen species (ROS) was observed in transgenic lines. The increased proline accumulation and ROS scavenging enzyme activities in transgenic plants over-expressing OsACA6 efficiently modulate the ROS machinery and proline biosynthesis through an integrative mechanism. Transcriptional profiling of these plants revealed altered expression of genes encoding many transcription factors, stress- and disease-related proteins, as well as signalling components. These results suggest that Ca²⁺ ATPases have diverse roles as regulators of many stress signalling pathways, leading to plant growth, development and stress tolerance.