Isolation of an osmotin-like protein gene from strawberry and analysis of the response of this gene to abiotic stresses

Suppression of Strawberry Anthracnose by Paenibacillus polymyxa TP3 In Situ and from a Distance

Strawberry is a popular fruit with valuable nutrition and an attractive fragrance, but its production and propagation are limited by various diseases, including anthracnose and gray mold. For disease management, biological control measures are environmentally friendly and good alternatives to fungicides to avoid crop losses, reduce carbon emissions, and improve food safety. In this study, Paenibacillus polymyxa TP3, which originated from the strawberry phyllosphere, was shown to antagonize the anthracnose fungal pathogen Colletotrichum siamense and reduce leaf symptoms on strawberry plants. Several mass spectra corresponding to fusaricidin were detected in the confrontation assay of P. polymyxa TP3 and C. siamense by image mass spectrometry. The transcription of fusA and fusG in the fusaricidin biosynthesis gene cluster increased while P. polymyxa TP3 was cultured in the medium containing the culture filtrate of C. siamense, as detected by reverse-transcription polymerase chain reaction, indicating the involvement of fusaricidins in P. polymyxa TP3 antagonism against the anthracnose pathogen. Further disease control assays demonstrated the time frame and spatial mode of P. polymyxa TP3-induced systemic resistance of strawberry against C. siamense. The transcript level of the marker gene FaPDF1.2 of the jasmonic acid pathway increased in strawberry leaves after drenching treatment with P. polymyxa TP3, and the callose deposition was enhanced by further flg22 treatment. In addition, P. polymyxa TP3 treatments of the strawberry mother plants reduced C. siamense infection in the daughter plants, which would be a potent feature for the application of P. polymyxa TP3 in strawberry nurseries and fields to reduce the impact of diseases, especially anthracnose.

Do Polystyrene Nanoplastics Have Similar Effects on Duckweed (Lemna minor L.) at Environmentally Relevant and Observed-Effect Concentrations?

Although the biological effects of nanoplastics (<100 nm in size) in aquatic environments have been increasingly investigated, almost all such studies have been performed at observed-effect concentrations (higher than 1 μg/mL). The use of observed-effect concentrations of nanoplastics can provide essential data for evaluating the potential risks, but how these results apply to the effects of concentrations of nanoplastics observed in the environment remains unclear. Here, we show that exposure to both positively and negatively charged nanoplastics at the observed-effect concentration (ranging from 0 to 50 μg/mL) can result in physiological changes of Lemna minor L., a typical flowering aquatic plant species, inducing H₂O₂ and O₂^- accumulation and even cell death. However, the nanoplastics at environmentally relevant concentrations (lower than 0.1 μg/mL) had no obvious effects on phenotype of L. minor. Moreover, nanoplastics at both observed-effect and environmentally relevant concentrations were adsorbed onto the roots and fronds of the plants, whereas uptake by the roots and fronds occurred only at the observed-effect concentration. Although no phenotypic changes across 30 generations of cultivation were observed when the plants were exposed to 0.015 μg/mL nanoplastics, the expression of genes related to the response to stimuli and to oxidative and osmotic stress was upregulated under both observed-effect and environmentally relevant concentrations. Our findings suggest that the long-term presence of nanoplastics at environmentally relevant concentrations might induce some variations in the transcription level and have potential threat to floating microphytes and aquatic ecosystems.

The Variability for the Biochemical Indicators at the Winter Wheat Assortment and Identifying the Sources with a High Antioxidant Activity

This study presents the variability of some biochemical indicators in the winter wheat assortments tested in south-western Oltenia (Romania) and identification of the sources showing a high antioxidant activity. The peroxidase activity has intensified as the stress induced by treatment with PEG of different concentrations and in different doses increased. Regarding the peroxidase content, among the varieties treated with PEG 10,000 25%, the majority of the Romanian varieties tested showed higher values of the PEG/control treatment ratio, which suggests tolerance to drought. In reverse, the activity of ascorbate peroxidase is lower in tolerant varieties. The varieties with a subunit report have been noted. Among them are the Izvor variety, known as the drought-tolerant variety, as well as other Romanian varieties: Alex, Delabrad, Lovrin 34, etc. An increased activity of catalase was present in most varieties, so there is the possibility of drought tolerance. Among the varieties highlighted are Romanian varieties (Dropia, Trivale, Nikifor, etc.) but also foreign varieties (Kristina, GH Hattyu, Karlygash, etc.). However, the correlation between yield index in the limited assortment and the antioxidant enzyme content ratios between PEG and control treatments does not exist, suggesting that none of these biochemical indicators are a selective indicator for drought tolerance under the experimental condition.

Arabidopsis OSMOTIN 34 Functions in the ABA Signaling Pathway and Is Regulated by Proteolysis

Plants have evolutionarily established resistance responses to a variety of abiotic stress conditions, in which ABA mediates the integrated regulation of these stress responses. Numerous proteins function at the transcription level or at the protein level when contributing to controls of the ABA signaling process. Although osmotin is identified as a salt-inducible protein, its function in the abiotic stress response is yet to be elucidated. To examine the role of Arabidopsis OSMOTIN 34 (OSM34) in the ABA signaling pathway, a deletion mutant osm34 generated by a CRISPR/Cas9 system and the double mutant osm34 osml (osmotin 34-like) were analyzed for various ABA responses. Both osm34 and osm34 osml showed reduced levels of ABA responses in seeds and leaves. Moreover, proline level and expression of the proline biosynthesis gene P5CS1 was significantly reduced in osm34 osml. Interestingly, OSM34 binds to SKP2A, an F-Box protein whose transcription is induced by ABA. The protein stability of OSM34 was determined to be under the control of the 26S proteasome. In conclusion, our data suggest that OSM34 functions as a positive regulator in the generation of ABA responses and is under post-translational control.

Molecular Characterization Revealed the Role of Thaumatin-Like Proteins of Bread Wheat in Stress Response

Thaumatin-like proteins (TLPs) are related to pathogenesis-related-5 (PR-5) family and involved in stress response. Herein, a total of 93 TLP genes were identified in the genome of Triticum aestivum. Further, we identified 26, 27, 39, and 37 TLP genes in the Brachypodium distachyon, Oryza sativa, Sorghum bicolor, and Zea mays genomes for comparative characterization, respectively. They could be grouped into small and long TLPs with conserved thaumatin signature motif. Tightly clustered genes exhibited conserved gene and protein structure. The physicochemical analyses suggested significant differences between small and long TLPs. Evolutionary analyses suggested the role of duplication events and purifying selection in the expansion of the TLP gene family. Expression analyses revealed the possible roles of TLPs in plant development and abiotic and fungal stress response. Recombinant expression of TaTLP2-B in Saccharomyces cerevisiae provided significant tolerance against cold, heat, osmotic, and salt stresses. The results depicted the importance of TLPs in cereal crops that would be highly useful in future crop improvement programs.

Osmotin: A Cationic Protein Leads to Improve Biotic and Abiotic Stress Tolerance in Plants

Research on biologically active compounds has been increased in order to improve plant protection against various environmental stresses. Among natural sources, plants are the fundamental material for studying these bioactive compounds as their immune system consists of many peptides, proteins, and hormones. Osmotin is a multifunctional stress-responsive protein belonging to pathogenesis-related 5 (PR-5) defense-related protein family, which is involved in inducing osmo-tolerance in plants. In this scenario, the accumulation of osmotin initiates abiotic and biotic signal transductions. These proteins work as antifungal agents against a broad range of fungal species by increasing plasma membrane permeability and dissipating the membrane potential of infecting fungi. Therefore, overexpression of tobacco osmotin protein in transgenic plants protects them from different stresses by reducing reactive oxygen species (ROS) production, limiting lipid peroxidation, initiating programmed cell death (PCD), and increasing proline content and scavenging enzyme activity. Other than osmotin, its homologous proteins, osmotin-like proteins (OLPs), also have dual function in plant defense against osmotic stress and have strong antifungal activity.

Osmotin-Like Protein Gene from Panax notoginseng Is Regulated by Jasmonic Acid and Involved in Defense Responses to Fusarium solani

Osmotin and osmotin-like proteins (OLPs) play important roles in plant defense responses. The full-length cDNA sequence of an OLP gene was cloned from Panax notoginseng using rapid amplification of cDNA-end technology and named PnOLP1. A quantitative reverse transcription-PCR analysis showed that the signaling molecules methyl jasmonate, salicylic acid, ethylene, and hydrogen peroxide induced PnOLP1 expression to different degrees. In addition, the expression level of PnOLP1 rapidly increased within 48 h of inoculating P. notoginseng with the root rot pathogen Fusarium solani. Subcellular localization revealed that PnOLP1 localized to the cell wall. A prokaryotic expression vector containing PnOLP1 was constructed and transformed into Escherichia coli BL21 (DE3), and in vitro antifungal assays were performed using the purified recombinant PnOLP1 protein. The recombinant PnOLP1 protein had strong inhibitory effects on the mycelial growth of F. oxysporum, F. graminearum, and F. solani. A plant PnOLP1-overexpression vector was constructed and transfected into tobacco, and the resistance of T2 transgenic tobacco against F. solani was significantly enhanced compared with wild-type tobacco. Moreover, a PnOLP1 RNAi vector was constructed and transferred to the P. notoginseng leaves for transient expression, and the decrease of PnOLP1 expression level in P. notoginseng leaves increased the susceptibility to F. solani. Thus, PnOLP1 is an important disease resistance gene involved in the defense responses of P. notoginseng to F. solani.

Thaumatin-like protein kinases: Molecular characterization and transcriptional profiling in five cereal crops

Thaumatin-like protein kinases (TLPKs) are defense related proteins having antimicrobial property. Herein, we identified two TLPKs in the genome of Brachypodium distachyon and Oryza sativa, four in Hordeum vulgare and Sorghum bicolor, and 16 in Triticum aestivum. All the TLPKs were located at only one chromosome in each plant except T. aestivum, where they were located on chromosome 2 and chromosome 3. Paralogous analysis suggested the occurrence of one duplication event (DE) in each B. distachyon and O. sativa, two in H. vulgare while four DEs in T. aestivum genome during the evolution of TLPKs. The majority of TLPKs were intron less, while a few contains one or two introns. The introns were found in each 0, 1 and 2 phase. Protein structure analysis suggested the occurrence of a thaumatin and a kinase domain with a transmembrane (TM) helix in each TLPK. Further, a thaumatin family signature motif "GX[GF]XCXT[GA]DCX(1,2)GX(2,3)C", a "REDDD" motif and 16 cysteine residues were found conserved in the majority of TLPKs. Expression analysis indicated variable expression of TLPKs in various tissues of different cereal crops. They were high expressing in reproductive tissues in B. distachyon, while in leaves in T. aestivum. Modulated expression of TaTLPKs in the presence of fungal pathogen, and heat, drought and salt stress in T. aestivum suggested their roles in stress response. Co-expression analysis showed interaction of TLPKs with various development and stress related genes. The results indicated diverse roles of TLPKs, which can be utilized for the development of eco-friendly pest resistant crops in future.

Identification of a strawberry NPR-like gene involved in negative regulation of the salicylic acid-mediated defense pathway

Hormonal modulation plays a central role in triggering various resistant responses to biotic and abiotic stresses in plants. In cultivated strawberry (Fragaria x ananassa), the salicylic acid (SA)-dependent defense pathway has been associated with resistance to Colletotrichum spp. and the other pathogens. To better understand the SA-mediated defense mechanisms in strawberry, we analyzed two strawberry cultivars treated with SA for their resistance to anthracnose and gene expression profiles at 6, 12, 24, and 48 hr post-treatment. Strawberry genes related to SA biosynthesis, perception, and signaling were identified from SA-responsive transcriptomes of the two cultivars, and the induction of 17 candidate genes upon SA treatment was confirmed by qRT-PCR. Given the pivotal role of the non-expressor of pathogenesis-related (NPR) family in controlling the SA-mediated defense signaling pathway, we then analyzed NPR orthologous genes in strawberry. From the expression profile, FaNPRL-1 [ortholog of FvNPRL-1 (gene20070 in F. vesca)] was identified as an NPR-like gene significantly induced after SA treatment in both cultivars. With a conserved BTB/POZ domain, ankyrin repeat domain, and nuclear localization signal, FvNPRL-1 was found phylogenetically closer to NPR3/NPR4 than NPR1 in Arabidopsis. Ectopic expression of FvNPRL-1 in the Arabidopsis thaliana wild type suppressed the SA-mediated PR1 expression and the resistance to Pseudomonas syringae pv. tomato DC3000. Transient expression of FvNPRL-1 fused with green fluorescent protein in Arabidopsis protoplasts showed that SA affected nuclear translocation of FvNPRL-1. FvNPRL-1 likely functions similar to Arabidopsis NPR3/NPR4 as a negative regulator of the SA-mediated defense.

An osmotin from the resurrection plant Tripogon loliiformis (TlOsm) confers tolerance to multiple abiotic stresses in transgenic rice

Osmotin is a key protein associated with abiotic and biotic stress response in plants. In this study, an osmotin from the resurrection plant Tripogon loliiformis (TlOsm) was characterized and functionally analyzed under abiotic stress conditions in T. loliiformis as well as in transgenic Nicotiana tabacum (tobacco) and Oryza sativa (rice) plants. Real-time PCR analysis on mixed elicitor cDNA libraries from T. loliiformis showed that TlOsm was upregulated a 1000-fold during the early stages of osmotic stresses (cold, drought, and salinity) in both shoots and roots but downregulated in shoots during heat stress. There was no change in TlOsm gene expression in roots of heat-stressed plants and during plant development. The plasma membrane localization of TlOsm was showed in fluorescent-tagged TlOsm tobacco plants using confocal laser scanning microscopic analysis. Transgenic rice plants expressing TlOsm were assessed for enhanced tolerance to salinity, drought and cold stresses. Constitutively expressed TlOsm in transgenic rice plants showed increased tolerance to cold, drought and salinity stress when compared with the wild-type and vector control counterparts. This was evidenced by maintained growth, retained higher water content and membrane integrity, and improved survival rate of TlOsm-expressing plants. The results thus indicate the involvement of TlOsm in plant response to multiple abiotic stresses, possibly through the signaling pathway, and highlight its potential applications for engineering crops with improved tolerance to cold, drought and salinity stress.

Identification and functional characterization of HbOsmotin from Hevea brasiliensis

Latex in the laticiferous cell network of Hevea brasiliensis tree is composed of cytoplasm that synthesizes natural rubber. Ethylene stimulation of the tree bark enhances latex production partly by prolonging the duration of latex flow during the tapping process. Here, we identified an osmotin-like cDNA sequence (HbOsmotin) from H. brasiliensis that belongs to the pathogenesis-related 5 (PR-5) gene family. The HbOsmotin protein is present in the lutoids of latex in H. brasiliensis, whereas in onion epidermal cells, this protein is predominantly distributed around the cell wall, suggesting that it may be secreted from the cytoplasm. We investigated the effects of exogenous ethylene on HbOsmotin transcription and protein accumulation in rubber latex, and further determined the protein function after osmotic stress in Arabidopsis. In regularly tapped trees, HbOsmotin expression was drastically inhibited in rubber latex after tapping, although the expression was subsequently recovered by ethylene stimulation. However, in virgin plants that had never been tapped, exogenous ethylene application slightly decreased HbOsmotin expression. HbOsmotin overexpression in Arabidopsis showed that HbOsmotin reduced the osmotic stress tolerance of the plant, which likely occurred by raising the water potential. These data indicated that HbOsmotin may contribute to osmotic regulation in laticiferous cells.

Isolation and Characterization of a Novel Pathogenesis-Related Protein Gene (GmPRP) with Induced Expression in Soybean (Glycine max) during Infection with Phytophthora sojae

Pathogenesis-related proteins (PR proteins) play crucial roles in the plant defense system. A novel PRP gene was isolated from highly resistant soybean infected with Phytophthora sojae (P. sojae) and was named GmPRP (GenBank accession number: KM506762). The amino acid sequences of GmPRP showed identities of 74%, 73%, 72% and 69% with PRP proteins from Vitis vinifera, Populus trichocarpa, Citrus sinensis and Theobroma cacao, respectively. Quantitative real-time reverse transcription PCR (qRT-PCR) data showed that the expression of GmPRP was highest in roots, followed by the stems and leaves. GmPRP expression was upregulated in soybean leaves infected with P. sojae. Similarly, GmPRP expression also responded to defense/stress signaling molecules, including salicylic acid (SA), ethylene (ET), abscisic acid (ABA) and jasmonic acid (JA). GmPRP was localized in the cell plasma membrane and cytoplasm. Recombinant GmPRP protein exhibited ribonuclease activity and significant inhibition of hyphal growth of P. sojae 1 in vitro. Overexpression of the GmPRP gene in T2 transgenic tobacco and T2 soybean plants resulted in enhanced resistance to Phytophthora nicotianae (P. nicotianae) and P. sojae race 1, respectively. These results indicated that the GmPRP protein played an important role in the defense of soybean against P. sojae infection.

Osmotin: a plant sentinel and a possible agonist of mammalian adiponectin

Osmotin is a stress responsive antifungal protein belonging to the pathogenesis-related (PR)-5 family that confers tolerance to both biotic and abiotic stresses in plants. Protective efforts of osmotin in plants range from high temperature to cold and salt to drought. It lyses the plasma membrane of the pathogens. It is widely distributed in fruits and vegetables. It is a differentially expressed and developmentally regulated protein that protects the cells from osmotic stress and invading pathogens as well, by structural or metabolic alterations. During stress conditions, osmotin helps in the accumulation of the osmolyte proline, which quenches reactive oxygen species and free radicals. Osmotin expression results in the accumulation of storage reserves and increases the shelf-life of fruits. It binds to a seven-transmembrane-domain receptor-like protein and induces programmed cell death in Saccharomyces cerevisiae through RAS2/cAMP signaling pathway. Adiponectin, produced in adipose tissues of mammals, is an insulin-sensitizing hormone. Strangely, osmotin acts like the mammalian hormone adiponectin in various in vitro and in vivo models. Adiponectin and osmotin, the two receptor binding proteins do not share sequence similarity at the amino acid level, but interestingly they have a similar structural and functional properties. In experimental mice, adiponectin inhibits endothelial cell proliferation and migration, primary tumor growth, and reduces atherosclerosis. This retrospective work examines the vital role of osmotin in plant defense and as a potential targeted therapeutic drug for humans.

Molecular cloning and functional characterization of an antifungal PR-5 protein from Ocimum basilicum

Pathogenesis-related (PR) proteins are involved in biotic and abiotic stress responses of plants and are grouped into 17 families (PR-1 to PR-17). PR-5 family includes proteins related to thaumatin and osmotin, with several members possessing antimicrobial properties. In this study, a PR-5 gene showing a high degree of homology with osmotin-like protein was isolated from sweet basil (Ocimum basilicum L.). A complete open reading frame consisting of 675 nucleotides, coding for a precursor protein, was obtained by PCR amplification. Based on sequence comparisons with tobacco osmotin and other osmotin-like proteins (OLPs), this protein was named ObOLP. The predicted mature protein is 225 amino acids in length and contains 16 cysteine residues that may potentially form eight disulfide bonds, a signature common to most PR-5 proteins. Among the various abiotic stress treatments tested, including high salt, mechanical wounding and exogenous phytohormone/elicitor treatments; methyl jasmonate (MeJA) and mechanical wounding significantly induced the expression of ObOLP gene. The coding sequence of ObOLP was cloned and expressed in a bacterial host resulting in a 25kDa recombinant-HIS tagged protein, displaying antifungal activity. The ObOLP protein sequence appears to contain an N-terminal signal peptide with signatures of secretory pathway. Further, our experimental data shows that ObOLP expression is regulated transcriptionally and in silico analysis suggests that it may be post-transcriptionally and post-translationally regulated through microRNAs and post-translational protein modifications, respectively. This study appears to be the first report of isolation and characterization of osmotin-like protein gene from O. basilicum.

Expression of an osmotin-like protein from Solanum nigrum confers drought tolerance in transgenic soybean

BACKGROUND

Drought is by far the most important environmental factor contributing to yield losses in crops, including soybeans [Glycine max (L.) Merr.]. To address this problem, a gene that encodes an osmotin-like protein isolated from Solanum nigrum var. americanum (SnOLP) driven by the UBQ3 promoter from Arabidopsis thaliana was transferred into the soybean genome by particle bombardment.

RESULTS

Two independently transformed soybean lines expressing SnOLP were produced. Segregation analyses indicated single-locus insertions for both lines. qPCR analysis suggested a single insertion of SnOLP in the genomes of both transgenic lines, but one copy of the hpt gene was inserted in the first line and two in the second line. Transgenic plants exhibited no remarkable phenotypic alterations in the seven analyzed generations. When subjected to water deficit, transgenic plants performed better than the control ones. Leaf physiological measurements revealed that transgenic soybean plants maintained higher leaf water potential at predawn, higher net CO2 assimilation rate, higher stomatal conductance and higher transpiration rate than non-transgenic plants. Grain production and 100-grain weight were affected by water supply. Decrease in grain productivity and 100-grain weight were observed for both transgenic and non-transgenic plants under water deficit; however, it was more pronounced for non-transgenic plants. Moreover, transgenic lines showed significantly higher 100-grain weight than non-transgenic plants under water shortage.

CONCLUSIONS

This is the first report showing that expression of SnOLP in transgenic soybeans improved physiological responses and yield components of plants when subjected to water deficit, highlighting the potential of this gene for biotechnological applications.

Differential expression of Arabidopsis defense-related genes in response to sulfur dioxide

Sulfur dioxide (SO(2)) is one of the most common and harmful air pollutants. To analyze cellular responses to SO(2), we investigated the transcript alterations, antioxidant enzyme activities and reactive oxygen species (ROS) levels in Arabidopsisthaliana (Col-0) exposed to SO(2). Transcriptional profiling using Affymetrix GeneChip technology identified 494 genes differentially expressed (≥2-fold change) in plants exposed to 30 mg m(-3) SO(2) for 72 h, including up-regulation of some defense-related genes encoding antioxidant enzymes and heat shock proteins. Moreover, numerous genes encoding pathogenesis-related proteins and enzymes required for the phenylpropanoid pathway and for cell wall modification were highly activated upon SO(2) exposure. We selected eight of the significantly differentially expressed defense-related genes for analysis using semi-quantitative RT-PCR and confirmed that their expression was up-regulated under SO(2) stress. In addition, SO(2) exposure caused the enhancement of ROS production, and also increased activities of antioxidant enzymes (superoxide dismutase, peroxidase, glutathione peroxidase and glutathione S-transferase) in Arabidopsis plants. Our results indicated that increased ROS may act as a signal to induce defense responses, which provide enhanced defense capacity to protect plants against SO(2) and other environmental stress. This is the first transcriptional profiling that identifies novel genes and pathways involved in SO(2) stress responses in plant cells. These data will be helpful for better understanding the molecular basis for plant adaptation to SO(2) stress.

High-efficiency transformation and selective tolerance against biotic and abiotic stress in mulberry, Morus indica cv. K2, by constitutive and inducible expression of tobacco osmotin

Osmotin and osmotin-like proteins are stress proteins belonging to the plant PR-5 group of proteins induced in several plant species in response to various types of biotic and abiotic stresses. We report here the overexpression of tobacco osmotin in transgenic mulberry plants under the control of a constitutive promoter (CaMV 35S) as well as a stress-inducible rd29A promoter. Southern analysis of the transgenic plants revealed the stable integration of the introduced genes in the transformants. Real-time PCR analysis provided evidence for the expression of osmotin in the transgenic plants under both the constitutive and stress-inducible promoters. Transgenic plants with the stress-inducible promoter were observed to better tolerate salt and drought stress than those with the constitutive promoter. Transgenic plants when subjected to simulated salinity and drought stress conditions showed better cellular membrane stability (CMS) and photosynthetic yield than non-transgenic plants under conditions of both salinity and drought stress. Proline levels were very high in transgenic plants with the constitutive promoter relative to those with the stress-inducible promoter. Fungal challenge undertaken with three fungal species known to cause serious losses to mulberry cultivation, namely, Fusarium pallidoroseum, Colletotrichum gloeosporioides and Colletotrichum dematium, revealed that transgenic plants with osmotin under control of the constitutive promoter had a better resistance than those with osmotin under the control of the stress-inducible promoter. Evaluation in next generation was undertaken by studying bud break in transgenic and non-transgenic plants under simulated drought (2% polyethylene glycol) and salt stress (200 mM NaCl) conditions. The axillary buds of the selected transgenic lines had a better bud break percentage under stressed conditions than buds from non-transgenic mulberry lines. A biotic assay with Bombyx mori indicated that osmotin protein had no undesirable effect on silkworm rearing and feeding. We therefore conclude that 35S transgenic plants are better suited for both abiotic stress also biotic challenges (fungal), while the rd29A transgenic plants are more responsive to drought.

Overexpression of osmotin gene confers tolerance to salt and drought stresses in transgenic tomato (Solanum lycopersicum L.)

Abiotic stresses, especially salinity and drought, are major limiting factors for plant growth and crop productivity. In an attempt to develop salt and drought tolerant tomato, a DNA cassette containing tobacco osmotin gene driven by a cauliflower mosaic virus 35S promoter was transferred to tomato (Solanum lycopersicum) via Agrobacterium-mediated transformation. Putative T0 transgenic plants were screened by PCR analysis. The selected transformants were evaluated for salt and drought stress tolerance by physiological analysis at T1 and T2 generations. Integration of the osmotin gene in transgenic T1 plants was verified by Southern blot hybridization. Transgenic expression of the osmotin gene was verified by RT-PCR and northern blotting in T1 plants. T1 progenies from both transformed and untransformed plants were tested for salt and drought tolerance by subjecting them to different levels of NaCl stress and by withholding water supply, respectively. Results from different physiological tests demonstrated enhanced tolerance to salt and drought stresses in transgenic plants harboring the osmotin gene as compared to the wild-type plants. The transgenic lines showed significantly higher relative water content, chlorophyll content, proline content, and leaf expansion than the wild-type plants under stress conditions. The present investigation clearly shows that overexpression of osmotin gene enhances salt and drought stress tolerance in transgenic tomato plants.

Molecular cloning of a PR-5 like protein gene from cherry tomato and analysis of the response of this gene to abiotic stresses

LePR-5, a putative PR5 like protein gene was amplified from a cherry tomato (Lycopersicon esculentum), which encodes a precursor protein of 250 amino acid residues, and shares high degrees of homology with a number of other PR5 genes. Expression of LePR-5 in different tomato organs was analyzed with Semi-quantitative RT-PCR, showing that LePR-5 expressed at different levels in leaves, stems, roots, flowers and fruits. In addition, expression of LePR-5 under different abiotic stresses was carried out at different time points. Three of the four tested abiotic stimuli, ethophen, salicylic acid and methyl jasmonate, triggered a significant induction of LePR-5 after treatment. However, LePR-5 was weaker induced by abscisic acid than by others. The positive responses of LePR-5 to the three abiotic stimuli suggested that LePR-5 may play an important role in response to abiotic stresses, and it may also be involved in plant defense system against pathogens. In addition, different expression patterns between tomato fruit and seedling suggested that LePR-5 may play a distinctive role in the defensive system protecting tomato fruit and seedling.

Gene expression analysis of molecular mechanisms of defense induced in Medicago truncatula parasitized by Orobanche crenata

The infection of Medicago truncatula Gaertn. roots with the obligate parasite Orobanche crenata Forsk. is a useful model for studying the molecular events involved in the legumes-parasite interaction. In order to gain insight into the identification of gene-regulatory elements involved in the resistance mechanism, the temporal expression pattern of ten defense-related genes was carried out using real-time quantitative reverse-transcription polymerase chain reaction assays. The induction of all of the analyzed transcripts significantly increased over a range from 2- to 321-fold higher than the control depending on the gene and time point. The transcriptional changes observed in response to O. crenata infection suggest that resistance could rely on both, the induction of general defense-related genes and more specific responses.

Assessment of adaptive evolution between wheat and rice as deduced from full-length common wheat cDNA sequence data and expression patterns

Background

Wheat is an allopolyploid plant that harbors a huge, complex genome. Therefore, accumulation of expressed sequence tags (ESTs) for wheat is becoming particularly important for functional genomics and molecular breeding. We prepared a comprehensive collection of ESTs from the various tissues that develop during the wheat life cycle and from tissues subjected to stress. We also examined their expression profiles in silico. As full-length cDNAs are indispensable to certify the collected ESTs and annotate the genes in the wheat genome, we performed a systematic survey and sequencing of the full-length cDNA clones. This sequence information is a valuable genetic resource for functional genomics and will enable carrying out comparative genomics in cereals.

Results

As part of the functional genomics and development of genomic wheat resources, we have generated a collection of full-length cDNAs from common wheat. By grouping the ESTs of recombinant clones randomly selected from the full-length cDNA library, we were able to sequence 6,162 independent clones with high accuracy. About 10% of the clones were wheat-unique genes, without any counterparts within the DNA database. Wheat clones that showed high homology to those of rice were selected in order to investigate their expression patterns in various tissues throughout the wheat life cycle and in response to abiotic-stress treatments. To assess the variability of genes that have evolved differently in wheat and rice, we calculated the substitution rate (Ka/Ks) of the counterparts in wheat and rice. Genes that were preferentially expressed in certain tissues or treatments had higher Ka/Ks values than those in other tissues and treatments, which suggests that the genes with the higher variability expressed in these tissues is under adaptive selection.

Conclusion

We have generated a high-quality full-length cDNA resource for common wheat, which is essential for continuation of the ongoing curation and annotation of the wheat genome. The data for each clone's expression in various tissues and stress treatments and its variability in wheat and rice as a result of their diversification are valuable tools for functional genomics in wheat and for comparative genomics in cereals.

Isolation of an 1-aminocyclopropane-1-carboxylate oxidase gene from mulberry (Morus alba L.) and analysis of the function of this gene in plant development and stresses response

Mulberry (Morus alba) is an important crop tree involved in sericulture and pharmaceuticals. To further understand the development and the environmental adaptability mechanism of mulberry, a cDNA of the gene MaACO1 encoding 1-aminocyclopropane-1-carboxylate oxidase was isolated from mulberry. This was used to investigate stress-responsive expression in mulberry. Developmental expression of ACC oxidase in mulberry leaves and spatial expression in mulberry flowers were also investigated. Damage and low-temperature treatment promoted the expression of MaACO1 in mulberry. In leaves, expression of the MaACO1 gene increased in cotyledons and the lowest leaves with leaf development, but showed reduced levels in emerging leaves. In flowers, the pollinated stigma showed the highest expression level, followed by the unpollinated stigma, ovary, and immature flowers. These results suggest that high MaACO1 expression may be predominantly associated with tissue aging or senescence in mulberry.

Screening and identification of putative allergens in berry fruits of the Rosaceae family: technical challenges

Cross-reactive proteins in small fruits of the Rosaceae family like strawberry, raspberry and blackberry revealed an unexpected complex IgE-reactivity pattern. Several copies of PR-10 and PR-14 proteins were detected by Southern blots in strawberry, raspberry and blackberry. In raspberry, the highest similarity at the DNA level for PR-10 and PR-14 (Rub i 1 and Rub i 3) was detected to strawberry sequences of Fra a 1 and Fra a 3. At the protein level, Rub i 1 and Rub i 3 showed more than 70% identity with homologous proteins of rosaceous fruits. Furthermore, raspberries contained additional putative allergens, e.g. class III acidic chitinases and cyclophilins. Blackberries were shown to share at least two well-known major fruit allergens with other rosaceous fruits, namely PR-10s and PR-14s homologous proteins. However the IgE-reactive proteins of small fruits are still not extensively investigated. The main challenges in studying small fruit allergens are the complexity of the fruit matrix, the diversity of physico-chemical properties of fruit proteins, the lack of appropriate protein extraction procedures and the missing information about the influence of processing treatments on food components.

Comparison of the expression profiles of susceptible and resistant Eucalyptus grandis exposed to Puccinia psidii Winter using SAGE

Eucalyptus grandis Hill ex Maiden and its hybrids are commonly planted by the Brazilian pulp and paper industry, but they are the most susceptible to the neotropical rust disease caused by Puccinia psidii Winter. In an initial attempt to understand the mechanisms of resistance, we constructed two contrasting Serial Analysis of Gene Expression (SAGE) libraries using susceptible and resistant individuals from a segregating half-sibling E. grandis population. Using the Z-test we identified tags differentially expressed between the libraries, preferentially 239 in the susceptible and 232 in the resistant type individuals. Using public (Expressed Sequence Tags) EST databases, 40 of the susceptible and 70 of the resistant tags matched ESTs and were annotated. By comparing the type of genes and their expression levels, distinct differences between the libraries were observed. Susceptible plants showed gene expression linked to leaf senescence, generalised stress responses and detoxification, and are apparently incapable of inducing a competent host defence response. On the other hand, resistant plants showed genes upregulated for cellular polarisation, cytoskeleton restructuring, vesicle transport, and cellulose and lignin biosynthesis. In the resistant individuals, evidence for systemic resistance, anti-oxidative responses and a hypersensitive response was also observed, although no R gene was identified.

Combinative effects of a bacterial type-III effector and a biocontrol bacterium on rice growth and disease resistance

Expression of HpaG(Xoo), a bacterial type-III effector, in transgenic plants induces disease resistance. Resistance also can be elicited by biocontrol bacteria. In both cases, plant growth is often promoted. Here we address whether biocontrol bacteria and HpaG(Xoo) can act together to provide better results in crop improvement. We studied effects of Pseudomonas cepacia on the rice variety R109 and the hpaG(Xoo)-expressing rice line HER1. Compared to R109, HER1 showed increased growth, grain yield, and defense responses toward diseases and salinity stress. Colonization of roots by P. cepacia caused 20% and 13% increase, in contrast to controls, in root growth of R109 and HER1. Growth of leaves and stems also increased in R109 but that of HER1 was inhibited. When P. cepacia colonization was subsequent to plant inoculation with Rhizoctonia solani, a pathogen that causes sheath blight, the disease was less severe than controls in both R109 and HER1; HER1, nevertheless, was more resistant, suggesting that P. cepacia and HpaG(Xoo) cooperate in inducing disease resistance. Several genes that critically regulate growth and defense behaved differentially in HER1 and R109 while responding to P. cepacia. In R109 leaves, the OsARF1 gene, which regulates plant growth, was expressed in consistence with growth promotion by P. cepacia. Inversely, OsARF1 expression was coincident with inhibition in growth of HER1 leaves. In both plants, the expression of OsEXP1, which encodes an expansin protein involved in plant growth,was concomitant with growth promotion in leaves instead of roots,in response to P. cepacia . We also studied OsMAPK, a gene that encodes a mitogen-activated protein kinase and controls defense responses toward salinity and infection by pathogens in rice. In response to P. cepacia, an early expression of OsMAPK was coincident with R109 resistance to the disease, while HER1 expressed the gene similarly whether P. cepacia was present or not. Evidently, P. cepacia and G(Xoo)-gene mediated resistance may act differently in rice growth and resistance. Whereas combinative effects of P. cepacia and HpaG(Xoo) in disease resistance have a great potential in agricultural use, it is interesting to study mechanisms that underlie interactions involving biocontrol bacteria, type-III effectors and pathogens.