Tolerance Of Tobacco Research Articles

Heterologous Overexpression of ZmHDZIV13 Enhanced Drought and Salt Tolerance in Arabidopsis and Tobacco

The homeodomain leucine zipper (HD-Zip) IV transcription factor is indispensable in the response of plants to abiotic stress. Systematic studies have been carried out in Arabidopsis, rice and other species from which a series of stress resistance-related genes have been isolated. However, the function of the HD-Zip IV protein in maize is not clear. In this study, we cloned the HD-Zip IV gene ZmHDZIV13 and identified its function in the stress response. Our phylogenetic analysis showed that ZmHDZIV13 and AtHDG11 had high homology and might have similar functions. The heterologous overexpression of ZmHDZIV13 in Arabidopsis resulted in sensitivity to abscisic acid (ABA), salt tolerance during germination and drought tolerance in seedlings. Under drought stress, the transgenic Arabidopsis showed stronger drought resistance than the wild-type (control). The malondialdehyde content of ZmHDZIV13 transgenic plants was lower than that of the control, and the relative water content and proline content were significantly higher than those of the control. After the drought was relieved, the expression levels of stress-related genes were up-regulated in transgenic Arabidopsis. These results show that ZmHDZIV13, as a stress-responsive transcription factor, plays a role in the positive regulation of abiotic stress tolerance and can regulate an ABA-dependent signaling pathway to regulate drought response in plants.

Agrobacterium-mediated transformation and in vitro evaluation of dehydration tolerance in transgenic tobacco harboring Ca-AFP gene

We have known that plant defensins have the main roles in biotic stress, especially antifungal activities. In addition, their functions on abiotic stress tolerance have been demonstrated on previous studies, but that information was still limited. Ca-AFP, a plant defensin gene derived from chickpea, was transformed into tobacco leaf disks by Agrobacterium method. After 16 weeks on selection media containing 15 mg/L hygromycin, some regeneration shoot lines were obtained. Four of them showed the positive bands on hpt gene and Ca-AFP gene by PCR screening. These lines were applied on in vitro evaluation of dehydration tolerance using rotary liquid culture, and the water-deficit stress was caused by 2% (w/v) PEG 6000. These four transgenic lines had better growth of adventitious roots (number of adventitious roots, total adventitious root length, and average of root length) and higher rate of biomass increase than the non-transgenic line. The result illustrated that the expression of Ca-AFP gene could mitigate the negative effect of water-deficit stress on transgenic tobacco lines under the in vitro stress condition. These transgenic tobacco lines are potential for water-deficit stress trials on greenhouse in the future.

Systematic analysis of the pectin methylesterase gene family in Nicotiana tabacum and reveal their multiple roles in plant development and abiotic stresses.

The pectin methylesterases (PMEs) play multiple roles in regulating plant development and responses to various stresses. In our study, a total of 121 PME genes were identified in the tobacco genome, which were clustered into two groups based on phylogenetic analysis together with Arabidopsis members. The investigations of gene structure and conserved motif indicated that exon/intron and motif organizations were relatively conserved in each group. Additionally, several stress-related elements were identified in the promoter region of these genes. The survey of duplication events revealed that segmental duplications were critical to the expansion of the PME gene family in tobacco. The expression profiles analysis revealed that these genes were expressed in various tissues and could be induced by diverse abiotic stresses. Notably, NtPME029 and NtPME043, were identified as homologues with AtPME3 and AtPME31, respectively. Furthermore, NtPME029 was highly expressed in roots and the over-expression of the NtPME029 gene could promote the development of roots. While NtPME043 could be induced by salt and ABA treatments, and the over-expression of the NtPME043 gene could significantly enhance the salt-stress tolerance in tobacco. Overall, these findings may shed light on the biological and functional characterization of NtPME genes in tobacco.

Comprehensive analysis of the GALACTINOL SYNTHASE (GolS) gene family in citrus and the function of CsGolS6 in stress tolerance.

Galactinol synthase (GolS) catalyzes the first and rate-limiting step in the synthesis of raffinose family of oligosaccharides (RFOs), which serve as storage and transport sugars, signal transducers, compatible solutes and antioxidants in higher plants. The present work aimed to assess the potential functions of citrus GolS in mechanisms of stress response and tolerance. By homology searches, eight GolS genes were found in the genomes of Citrus sinensis and C. clementina. Phylogenetic analysis showed that there is a GolS ortholog in C. clementina for each C. sinensis GolS, which have evolved differently from those of Arabidopsis thaliana. Transcriptional analysis indicated that most C. sinensis GolS (CsGolS) genes show a low-level tissue-specific and stress-inducible expression in response to drought and salt stress treatments, as well as to ‘Candidatus Liberibacter asiaticus’ infection. CsGolS6 overexpression resulted in improved tobacco tolerance to drought and salt stresses, contributing to an increased mesophyll cell expansion, photosynthesis and plant growth. Primary metabolite profiling revealed no significant changes in endogenous galactinol, but different extents of reduction of raffinose in the transgenic plants. On the other hand, a significant increase in the levels of metabolites with antioxidant properties, such as ascorbate, dehydroascorbate, alfa-tocopherol and spermidine, was observed in the transgenic plants. These results bring evidence that CsGolS6 is a potential candidate for improving stress tolerance in citrus and other plants.

The sweet potato transcription factor IbbHLH33 enhances chilling tolerance in transgenic tobacco

Chilling is an important abiotic stress in plants. Sweet potato is sensitive to cold damage due to its tropical origin. In this study, we identified a basic helix-loop-helix (bHLH) gene, IbbHLH33, from our cold-tolerance-related transcriptomic data. Further analyses revealed that IbbHLH33 encoded a nuclear protein and was most closely related to AtbHLH33. RT-qPCR analysis showed that IbbHLH33 was expressed at the highest level in the roots, and its expression was strongly induced by low temperature (4 °C), H<sub>2</sub>O<sub>2</sub> and abscisic acid (ABA) treatments. Transgenic tobacco plants overexpressing IbbHLH33 were obtained by Agrobacterium-mediated transformation, which enhanced the chilling resistance of tobacco. At low temperatures, the proline content, superoxide dismutase (SOD) activity and malondialdehyde (MDA) content increased significantly, while the relative conductivity decreased significantly. At the same time, the expression of proline synthesis related genes and antioxidant activity related genes increased, while the expression of ABA synthesis related genes decreased. The results showed that IbbHLH33 is a transcription factor encoding a gene of the bHLH family that regulates chilling tolerance. In conclusion, these data suggest that IbbHLH33 has the potential to improve chilling tolerance in tobacco and other plants.

IbMYB308, a Sweet Potato R2R3-MYB Gene, Improves Salt Stress Tolerance in Transgenic Tobacco

The MYB (v-myb avian myeloblastosis viral oncogene homolog) transcription factor family plays an important role in plant growth, development, and response to biotic and abiotic stresses. However, the gene functions of MYB transcription factors in sweet potato (Ipomoea batatas (L.) Lam) have not been elucidated. In this study, an MYB transcription factor gene, IbMYB308, was identified and isolated from sweet potato. Multiple sequence alignment showed that IbMYB308 is a typical R2R3-MYB transcription factor. Further, quantitative real-time PCR (qRT-PCR) analysis revealed that IbMYB308 was expressed in root, stem, and, especially, leaf tissues. Moreover, it showed that IbMYB308 had a tissue-specific profile. The experiment also showed that the expression of IbMYB308 was induced by different abiotic stresses (20% PEG-6000, 200 mM NaCl, and 20% H2O2). After a 200 mM NaCl treatment, the expression of several stress-related genes (SOD, POD, APX, and P5CS) was upregulation in transgenic plants, and the CAT activity, POD activity, proline content, and protein content in transgenic tobacco had increased, while MDA content had decreased. In conclusion, this study demonstrated that IbMYB308 could improve salt stress tolerance in transgenic tobacco. These findings lay a foundation for future studies on the R2R3-MYB gene family of sweet potato and suggest that IbMYB308 could potentially be used as an important positive factor in transgenic plant breeding to improve salt stress tolerance in sweet potato plants.

IbTLD modulates reactive oxygen species scavenging and DNA protection to confer salinity stress tolerance in tobacco

Plants accumulate reactive oxygen species (ROS) that may damage the cells under prolonged stress conditions. Reduction of the excessive ROS production can alleviate oxidative damage and enhance the survival rates under stress. TLDc–containing protein (TLD) was reported to confer tolerance to oxidative stress, but the regulatory mechanism of TLD remains unclear. In this study, we ectopically overexpressed the Ipomoea batatas TLDc gene (IbTLD) in tobacco and characterized its functions. RNA-sequencing analysis and Gene Ontology term enrichment analysis revealed that IbTLD up-regulates auxin-responsive genes in response to oxidative stress. Under salinity stress, the IbTLD transgenic lines showed higher germination rates, chlorophyll contents, and root lengths than wild type (W38). In addition, the IbTLD transgenic lines showed higher expression of ROS scavenging genes, nudix hydrolases, ROS scavenging enzyme activity, and lesser DNA damage compared to W38 under salinity stress. Therefore, our results suggest that IbTLD activates the expression of ROS scavenging genes and confers tolerance to salinity stress in planta.

Carex rigescens caffeic acid O-methyltransferase gene CrCOMT confer melatonin-mediated drought tolerance in transgenic tobacco.

Melatonin is an important, multifunctional protective agent against a variety of abiotic and biotic stressors in plants. Caffeic acid O-methyltransferase (COMT) catalyzes the last step of melatonin synthesis in plants and reportedly participates in the regulation of stress response and tolerance. However, few studies have reported its function in melatonin-mediated drought resistance. In this study, CrCOMT was identified and was strongly induced by drought stress in Carex rigescens. CrCOMT overexpression in transgenic tobacco increased tolerance to drought stress with high levels of seed germination, relative water content, and survival rates. CrCOMT overexpression in tobacco improved membrane stability, and plants exhibited lower relative electrolytic leakage and malondialdehyde content, as well as higher photochemical efficiency than the wildtype (WT) under drought stress. The transgenic plants also had higher levels of proline accumulation and antioxidant enzyme activity, which decreased oxidative stress damage due to reactive oxygen species (ROS) hyperaccumulation under drought stress. The transcription of drought stress response and ROS scavenging genes was significantly higher in the CrCOMT overexpression plants than in the WT plants. In addition, CrCOMT transgenic tobacco plants exhibited higher melatonin content under drought stress conditions. Exogenous melatonin was applied to C. rigescens under drought stress to confirm the function of melatonin in mediating drought tolerance; the relative water content and proline content were higher, and the relative electrolytic leakage was lower in melatonin-treated C. rigescens than in the untreated plants. In summary, these results show that CrCOMT plays a positive role in plant drought stress tolerance by regulating endogenous melatonin content.

Application of 2,4-Epibrassinolide Improves Drought Tolerance in Tobacco through Physiological and Biochemical Mechanisms.

Simple SummaryDrought stress is one of the most serious abiotic stresses and negatively affects crop growth and development. Given global climate change, it is important to identify effective methods of alleviating drought stress effects. Brassinosteroids (2,4-epibrassinolide-EBR) play an important role in mitigating the negative effects of drought stress on plants. Therefore, this study evaluated the role of EBR in improving drought tolerance. The results demonstrated that EBR application improved drought tolerance by strengthening the enzymatic antioxidant defense system and osmoregulation to scavenge reactive oxygen species. EBR application improved BR and IAA phytohormone content and improved drought tolerance by upregulating genes related to their respective signaling pathways. Therefore, EBR application is an effective strategy for improving drought tolerance in crop plants.Drought stress is a major abiotic stress that hinders plant growth and development. Brassinosteroids (BR), including 2,4-epibrassinolide (EBR), play important roles in plant growth, development, and responses to abiotic stresses, including drought stress. This work investigates exogenous EBR application roles in improving drought tolerance in tobacco. Tobacco plants were divided into three groups: WW (well-watered), DS (drought stress), and DSB (drought stress + 0.05 mM EBR). The results revealed that DS decreased the leaf thickness (LT), whereas EBR application upregulated genes related to cell expansion, which were induced by the BR (DWF4, HERK2, and BZR1) and IAA (ARF9, ARF6, PIN1, SAUR19, and ABP1) signaling pathway. This promoted LT by 28%, increasing plant adaptation. Furthermore, EBR application improved SOD (22%), POD (11%), and CAT (5%) enzyme activities and their related genes expression (FeSOD, POD, and CAT) along with a higher accumulation of osmoregulatory substances such as proline (29%) and soluble sugars (14%) under DS and conferred drought tolerance. Finally, EBR application augmented the auxin (IAA) (21%) and brassinolide (131%) contents and upregulated genes related to drought tolerance induced by the BR (BRL3 and BZR2) and IAA (YUCCA6, SAUR32, and IAA26) signaling pathways. These results suggest that it could play an important role in improving mechanisms of drought tolerance in tobacco.

Molecular cloning and functional analysis of a Chrysanthemum vestitum GME homolog that enhances drought tolerance in transgenic tobacco

GDP-mannose 3, 5-epimerase (GME, EC 5.1.3.18), a key enzyme in the ascorbic acid synthesis pathway, catalyzes the conversion of GDP-D-mannose to GDP-l-galactose in higher plants. Here, a homolog of GME was isolated from Chrysanthemum vestitum. The cDNA sequence of CvGME was 1131 bp and contained a complete open reading frame encoding a protein comprising 376 amino acids. Quantitative real-time PCR analysis revealed that CvGME was most highly expressed in the stems and roots. Phylogenetic analysis showed that CvGME was closely related to LsGME from Lactuca sativa. Subcellular localization studies revealed that CvGME was localized in the nucleus. Heterologous expression of CvGME in transgenic tobacco plants increased the ascorbic acid content in the leaves. In addition, overexpression of CvGME reduced the malondialdehyde content and increased superoxide dismutase and peroxidase activity in tobacco leaves compared to those in the wild-type plants under drought stress conditions, explaining the increased drought tolerance of transgenic tobacco lines. These results suggest that CvGME can effectively enhance the tolerance of plants to drought by increasing the ascorbic acid content, which may help improve the drought tolerance of chrysanthemums through molecular breeding.

NtCOMT1 responsible for phytomelatonin biosynthesis confers drought tolerance in Nicotiana tabacum

Nicotiana tabacum (tobacco) is one of the most important industrial crops and its productivity is vulnerable to drought, particularly in Yunnan province, China due to the long water-deficit spring. Here, we aimed at identifying caffeic acid O-methyltransferase (COMT) in melatonin biosynthesis to provide genetic resources against drought tolerance of tobacco. The integration of the genome-wide identification, phylogenetic relationships, and conserved domain/motif analysis revealed that NtCOMT1 could be the probable functional COMT homolog for melatonin production. In vitro enzyme activity test approved that NtCOMT1 enabled the conversion of N-acetylserotonin into melatonin, occurring both in the cytoplasm and nucleus by subcellular localization analysis. The Km and Vmax values for NtCOMT1 at the optimum temperature (30 °C) were 266.0 μM and 2.155 nmol/min/mg protein. NtCOMT1 was significantly induced by drought stress; whereby if this gene functioned on promoting drought resistance was further conducted. Overexpression of NtCOMT1 resulted in decreased wilting in transgenic tobacco plants subjected to dehydration treatment. The combinatorial effects of NtCOMT1 in increasing melatonin content, inducing antioxidant system, and elevating the expression of drought-related genes could deliver the drought tolerance in tobacco. The characterization of NtCOMT1 may represent a solution to cope with the increasing drought stress in tobacco production in Yunnan province.

RmZAT10, a novel Cys2/His2 zinc finger transcription factor of Rosa multiflora, functions in cold tolerance through modulation of proline biosynthesis and ROS homeostasis

The Cys2/His2-type (C2H2) zinc finger transcription factor (TF) consists of a significant gene family that has an effect on development process regulation and a wide range of stress responses, whereas the roles and regulatory pathways of the majority of C2H2-type zinc finger TFs remain unclear. Here, we characterized a C2H2-type zinc finger TF ( RmZAT10 ) from Rosa multiflora . RmZAT10 was mainly expressed in leaves and located in the nucleus. RmZAT10 was rapidly up-regulated during dehydration, cold as well as ABA treatment, with the maximal induction under cold stress. RmZAT10 overexpression facilitated the cold tolerance of tobacco, while gene silencing caused by virus-induced gene silencing (VIGS) of RmZAT10 within R.multiflora led to elevated cold sensitivity. Transgenic tobacco accumulated a larger amount of proline, consistent with elevated the expression level of P5CS (Δ -1-pyrroline-5-carboxylate synthetase ). Nevertheless, the VIGS plant achieved the opposing trend. The treatment using 24-epi-brassinolide caused transgenic tobacco plants more sensitive to cold, while exogenous proline partially restored cold tolerance of the VIGS plants. In addition, RmZAT10 could bind specifically to and activate the promoter of RmP5CS. The above results revealed the role played by RmZAT10 in cold tolerance through the modulation of proline biosynthesis and ROS homeostasis. • RmZAT10 is induced by cold, dehydration and ABA treatments, especially prominent under cold stress. • RmZAT10 overexpression enhanced the cold tolerance in tobacco, while VIGS of RmZAT10 increased cold susceptibility. • RmZAT10 played a role in cold tolerance through the modulation of proline biosynthesis and ROS homeostasis.

Herbaceous peony AP2/ERF transcription factor binds the promoter of the tryptophan decarboxylase gene to enhance high-temperature stress tolerance.

Global warming has multifarious adverse effects on plant growth and productivity. Nonetheless, the effects of endogenous phytomelatonin on the high-temperature resistance of plants and the underlying genetic mechanisms remain unclear. Here, herbaceous peony (Paeonia lactiflora Pall.) tryptophan decarboxylase (TDC) gene involved in phytomelatonin biosynthesis was shown to respond to high-temperature stress at the transcriptional level, and its transcript level was positively correlated with phytomelatonin production. Moreover, overexpression of PlTDC enhanced phytomelatonin production and high-temperature stress tolerance in transgenic tobacco, while silencing PlTDC expression decreased these parameters in P. lactiflora. In addition, a 2402 bp promoter fragment of PlTDC was isolated, and DNA pull-down assay revealed that one APETALA2/ethylene-responsive element-binding factor (AP2/ERF) transcription factor, PlTOE3, could specifically activate the PlTDC promoter, which was further verified by yeast one-hybrid assay and luciferase reporter assay. PlTOE3 was a nucleus-localized protein, and its transcript level responded to high-temperature stress. Additionally, transgenic tobacco overexpressing PlTOE3 showed enhanced phytomelatonin production and high-temperature stress tolerance, while silencing PlTDC expression obtained the opposite results. These results illustrated that PlTOE3 bound the PlTDC promoter to enhance high-temperature stress tolerance by increasing phytomelatonin production in P. lactiflora.

Functional analysis of PagNAC045 transcription factor that improves salt and ABA tolerance in transgenic tobacco

BackgroundSalt stress causes inhibition of plant growth and development, and always leads to an increasing threat to plant agriculture. Transcription factors regulate the expression of various genes for stress response and adaptation. It’s crucial to reveal the regulatory mechanisms of transcription factors in the response to salt stress.ResultsA salt-inducible NAC transcription factor gene PagNAC045 was isolated from Populus alba×P. glandulosa. The PagNAC045 had a high sequence similarity with NAC045 (Potri.007G099400.1) in P. trichocarpa, and they both contained the same conserved motifs 1 and 2, which constitute the highly conserved NAM domain at the N-terminus. Protein-protein interaction (PPI) prediction showed that PagNAC045 potentially interacts with many proteins involved in plant hormone signaling, DNA-binding and transcriptional regulation. The results of subcellular localization and transient expression in tobacco leaves confirmed the nuclear localization of PagNAC045. Yeast two-hybrid revealed that PagNAC045 protein exhibits transcriptional activation property and the activation domain located in its C-terminus. In addition, the 1063 bp promoter of PagNAC045 was able to drive GUS gene expression in the leaves and roots. In poplar leaves and roots, PagNAC045 expression increased significantly by salt and ABA treatments. Tobacco seedlings overexpressing PagNAC045 exhibited enhanced tolerance to NaCl and ABA compared to the wild-type (WT). Yeast one-hybrid assay demonstrated that a bHLH104-like transcription factor can bind to the promoter sequence of PagNAC045.ConclusionThe PagNAC045 functions as positive regulator in plant responses to NaCl and ABA-mediated stresses.

NtIAA26 positively regulates salt tolerance in tobacco by modulating potassium uptake and antioxidant activity

NtIAA26 positively regulates salt tolerance in tobacco by modulating potassium uptake and antioxidant activity

Mutation of NtNRAMP3 improves cadmium tolerance and its accumulation in tobacco leaves by regulating the subcellular distribution of cadmium

Cadmium (Cd) is a harmful element that affects plant growth and development. Genetic improvements could be applied for enhancing Cd tolerance and accumulation in plants. Here, a novel Cd stress-induced gene, NtNRAMP3, was identified in tobacco. We constructed two NtNRAMP3-knockout (KO) tobacco lines using the CRISPR/Cas9 system, which enhanced Cd tolerance and Cd accumulation in tobacco leaves compared with those in the wildtype (WT). Subcellular localization analysis suggested that NtNRAMP3 is a tonoplast protein and GUS (β-glucuronidase) histochemical analysis showed that NtNRAMP3 is highly expressed in the conductive tissue of leaves. NtNRAMP3-KO tobacco showed reduced Cd translation from vacuole to cytosol in leaves compared with the WT, and its vacuolar Cd concentration was significantly higher (20.78–22.81%) than that in the WT; in contrast, Cd concentration in the cytosol was reduced by 13.72–20.15%, preventing chlorophyll degradation and reducing reactive oxygen species accumulation in the leaves. Our findings demonstrate that NtNRAMP3 is involved in regulating Cd subcellular distribution (controlling Cd transport from vacuoles to the cytosol) and affects Cd tolerance and its accumulation in tobacco. This provides a key candidate gene to improve the phytoremediation efficiency of plants via genetic engineering.

Cytological and physiological tolerance of transgenic tobacco to Cd stress is enhanced by the ectopic expression of SmZIP8

Zrt and Irt-like proteins (ZIPs) are responsible for transporting various divalent metal cations. However, information about the characteristics of the cellular and physiological tolerance of plant ZIPs to Cd stress is still limited. The expression levels of SmZIP8 in Salix matsudana Koidz were upregulated by Cd stress. The complete length of SmZIP8 from S. matsudana was cloned, and transgenic tobacco was obtained by Agrobacterium-mediated transformation. Then, the tolerance to Cd stress of wild-type (WT) and transgenic tobacco seedlings was analyzed and compared by studying the cytotoxicity of the root tip cells, photosynthetic parameters, histochemical staining of O2− and H2O2, the activities of antioxidant enzymes, and malondialdehyde content under Cd stress. In comparison with WT tobacco, the ectopic expression of SmZIP8 in tobacco promoted the cytological tolerance of the transgenic tobacco to Cd stress by reducing cell damage, raising the mitotic indexes, and reducing the rate of chromosome aberration of the root cells. Meanwhile, the results of increased photosynthetic capacity, decreased oxidative damage, and activated antioxidant enzymes showed that the physiological tolerance of transgenic tobacco to Cd was enhanced. The principal component analysis for the above physiological parameters explained 96.08% of the total variance (PC1, 77.77%; PC2, 18.31%), indicating a significant difference in Cd tolerance abilities between the tobacco expressing SmZIP8 and WT tobacco. Therefore, SmZIP8 may be considered as an important genetic resource for the phytoremediation of Cd or other heavy metal pollution via the use of transgenic plants obtained through genetic transformation.

Expression of a sphingomyelinase‐coding gene from Trichoderma harzianum conferred bacterial tolerance in tobacco

AbstractDiseases caused by bacteria are an important and widespread constraint, occurring in almost all crops, including vegetables, pulses, cereals, ornamentals, fruit and forages. Although several strategies have been developed to obtain disease resistance in plants using genetic engineering, few studies have effectively demonstrated the control of bacterial diseases. It has previously been reported that a gene encoding a sphingomyelinase (ThSMase), identified in Trichoderma harzianum, is up‐regulated during biocontrol against phytopathogens, and this may have biotechnological applications. SMases are involved in multiple cellular functions, including the immune response against pathogens. We hypothesized that the expression of this gene from fungi in transgenic tobacco could generate resistance to plant pathogens. ThSMase was cloned under control of the double CaMV 35S promoter plus a leader sequence from alfalfa mosaic virus (AMV), and stably introduced and expressed in tobacco. Reverse transcription‐quantitative PCR analysis revealed that the ThSMase gene was expressed at similar levels in all transgenic lines tested. Our results showed no statistically significant difference in susceptibility after challenging transgenic and nontransgenic lines with the fungus Sclerotinia sclerotiorum. However, transgenic tobacco plants revealed a significant resistance to the bacterium Pseudomonas syringae pv. tabaci, and a tolerance to Xylella fastidiosa. Our results demonstrated the strong potential of ThSMase in biotechnological processes such as molecular breeding of the plants.

Thymol improves salinity tolerance of tobacco by increasing the sodium ion efflux and enhancing the content of nitric oxide and glutathione

Background and objectiveSalt stress is one of the most important abiotic stresses affecting the yield and quality of tobacco (Nicotiana tabacum). Thymol (a natural medicine) has been widely used in medical research because of its antibacterial and anti-inflammatory activities. However, the influence of thymol on the root growth of tobacco is not fully elucidated. In this study, the regulatory effects of different concentrations of thymol were investigated.MethodologyHere, histochemical staining and biochemical methods, non-invasive micro-test technology (NMT), and qPCR assay were performed to investigate the effect of thymol and mechanism of it improving salinity tolerance in tobacco seedlings.ResultsIn this study, our results showed that thymol rescued root growth from salt stress by ameliorating ROS accumulation, lipid peroxidation, and cell death. Furthermore, thymol enhanced contents of NO and GSH to repress ROS accumulation, further protecting the stability of the cell membrane. And, thymol improved Na+ efflux and the expression of SOS1, HKT1, and NHX1, thus protecting the stability of Na+ and K+.ConclusionOur study confirmed the protecting effect of thymol in tobacco under salt stress, and we also identified the mechanism of it, involving dynamic regulation of antioxidant system and the maintenance of Na+ homeostasis. It can be a new method to improve salinity tolerance in plants.

Functional Identification of ICE Transcription Factors in Rubber Tree

ICE (inducer of CBF expression) is a positive regulator of cold signaling pathway in plants. Identification of ICE transcription factors is important for the sustainable development of the natural rubber planting industry in nontraditional regions where sudden cold waves often occur. In this study, five ICE genes were isolated from genome of rubber tree (Hevea brasiliensis Muell. Arg.) for analysing tolerance to cold stress. They shared an ICE-specific region in the highly conserved bHLH-ZIP domain and were localized in the nucleus. The HbICEs were different in transcript abundance and expression patterns in response to cold and drought stresses and among different rubber tree clones. Generally, the expression level of HbICEs was significantly higher in the cold-tolerant rubber tree clones than that in the cold-sensitive rubber tree clones. Overexpression of HbICE1, HbICE2, and HbICE4 significantly enhanced the cold tolerance of transgenic Arabidopsis and tobacco, which showed a significant increase in chlorophyll content and decrease in relative water content and conductivity at the early stage of cold stress in comparison with wild-type plants. Furthermore, overexpression of HbICE2 and HbICE4, but also HbICE1 enhanced drought tolerance in transgenic Arabidopsis. The cold tolerance of rubber tree clones is positively controlled by the expression level of HbICE1, HbICE2, and HbICE4.