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Journal Cover Plant Molecular Biology     [SJR: 1.769]   [H-I: 112]
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   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1573-5028 - ISSN (Online) 0167-4412
   Published by Springer-Verlag Homepage  [2210 journals]
  • Biofortification of rice with lysine using endogenous histones
    • Abstract: Abstract Rice is the most consumed cereal grain in the world, but deficient in the essential amino acid lysine. Therefore, people in developing countries with limited food diversity who rely on rice as their major food source may suffer from malnutrition. Biofortification of stable crops by genetic engineering provides a fast and sustainable method to solve this problem. In this study, two endogenous rice lysine-rich histone proteins, RLRH1 and RLRH2, were over-expressed in rice seeds to achieve lysine biofortification. Their protein sequences passed an allergic sequence-based homology test. Their accumulations in rice seeds were raised to a moderate level by the use of a modified rice glutelin 1 promoter with lowered expression strength to avoid the occurrence of physiological abnormalities like unfolded protein response. The expressed proteins were further targeted to protein storage vacuoles for stable storage using a glutelin 1 signal peptide. The lysine content in the transgenic rice seeds was enhanced by up to 35 %, while other essential amino acids remained balanced, meeting the nutritional standards of the World Health Organization. No obvious unfolded protein response was detected. Different degrees of chalkiness, however, were detected in the transgenic seeds, and were positively correlated with both the levels of accumulated protein and lysine enhancement. This study offered a solution to the lysine deficiency in rice, while at the same time addressing concerns about food safety and physiological abnormalities in biofortified crops.
      PubDate: 2015-02-01
  • Tissue-specific expression of a soybean hypersensitive-induced response
           (HIR) protein gene promoter
    • Abstract: Abstract A Glycine max gene encoding a putative protein similar to hypersensitive-induced response proteins (HIR) was identified as a gene with preferred expressions in flowers and developing seeds by whole transcriptome gene expression profiling. Its promoter gm-hir1 was cloned and revealed to strongly express a fluorescence reporter gene primarily in integuments, anther tapetum, and seed coat with unique tissue-specificity. Expression in the inner integument was apparent prior to pollination, while expression in the outer integument started to develop from the micropylar end outward as the embryo matured. A 5′-deletion study showed that the promoter can be truncated to 600 bp long relative to the translation start site without affecting expression. A positive regulatory element was identified between 600 and 481 bp that controls expression in the inner integument, with no noticeable effect on expression in the outer integument or tapetum. Additionally, removal of the 5′UTR intron had no effect on levels or location of gm-hir1 expression while truncation to 370 bp resulted in a complete loss of expression suggesting that elements controlling both the outer integument and tapetum expression are located within the 481–370 bp region.
      PubDate: 2015-02-01
  • Rice phenylalanine ammonia-lyase gene OsPAL4 is associated with broad
           spectrum disease resistance
    • Abstract: Abstract Most agronomically important traits, including resistance against pathogens, are governed by quantitative trait loci (QTL). QTL-mediated resistance shows promise of being effective and long-lasting against diverse pathogens. Identification of genes controlling QTL-based disease resistance contributes to breeding for cultivars that exhibit high and stable resistance. Several defense response genes have been successfully used as good predictors and contributors to QTL-based resistance against several devastating rice diseases. In this study, we identified and characterized a rice (Oryza sativa) mutant line containing a 750 bp deletion in the second exon of OsPAL4, a member of the phenylalanine ammonia-lyase gene family. OsPAL4 clusters with three additional OsPAL genes that co-localize with QTL for bacterial blight and sheath blight disease resistance on rice chromosome 2. Self-pollination of heterozygous ospal4 mutant lines produced no homozygous progeny, suggesting that homozygosity for the mutation is lethal. The heterozygous ospal4 mutant line exhibited increased susceptibility to three distinct rice diseases, bacterial blight, sheath blight, and rice blast. Mutation of OsPAL4 increased expression of the OsPAL2 gene and decreased the expression of the unlinked OsPAL6 gene. OsPAL2 function is not redundant because the changes in expression did not compensate for loss of disease resistance. OsPAL6 co-localizes with a QTL for rice blast resistance, and is down-regulated in the ospal4 mutant line; this may explain enhanced susceptibility to Magnoporthe oryzae. Overall, these results suggest that OsPAL4 and possibly OsPAL6 are key contributors to resistance governed by QTL and are potential breeding targets for improved broad-spectrum disease resistance in rice.
      PubDate: 2015-02-01
  • The Arabidopsis MYB96 transcription factor plays a role in seed dormancy
    • Abstract: Abstract Seed dormancy facilitates to endure environmental disadvantages by confining embryonic growth until the seeds encounter favorable environmental conditions for germination. Abscisic acid (ABA) and gibberellic acid (GA) play a pivotal role in the determination of the seed dormancy state. ABA establishes seed dormancy, while GA triggers seed germination. Here, we demonstrate that MYB96 contributes to the fine-tuning of seed dormancy regulation through the coordination of ABA and GA metabolism. The MYB96-deficient myb96-1 seeds germinated earlier than wild-type seeds, whereas delayed germination was observed in the activation-tagging myb96-1D seeds. The differences in germination rate disappeared after stratification or after-ripening. The MYB96 transcription factor positively regulates ABA biosynthesis genes 9-CIS-EPOXYCAROTENOID DIOXYGENASE 2 (NCED2), NCED5, NCED6, and NCED9, and also affects GA biosynthetic genes GA3ox1 and GA20ox1. Notably, MYB96 directly binds to the promoters of NCED2 and NCED6, primarily modulating ABA biosynthesis, which subsequently influences GA metabolism. In agreement with this, hyperdormancy of myb96-1D seeds was recovered by an ABA biosynthesis inhibitor fluridone, while hypodormancy of myb96-1 seeds was suppressed by a GA biosynthesis inhibitor paclobutrazol (PAC). Taken together, the metabolic balance of ABA and GA underlies MYB96 control of primary seed dormancy.
      PubDate: 2015-01-24
  • The activity of the artemisinic aldehyde Δ11(13) reductase promoter
           is important for artemisinin yield in different chemotypes of Artemisia
           annua L.
    • Abstract: Abstract The artemisinic aldehyde double bond reductase (DBR2) plays an important role in the biosynthesis of the antimalarial artemisinin in Artemisia annua. Artemisinic aldehyde is reduced into dihydroartemisinic aldehyde by DBR2. Artemisinic aldehyde can also be oxidized by amorpha-4,11-diene 12-hydroxylase and/or aldehyde dehydrogenase 1 to artemisinic acid, a precursor of arteannuin B. In order to better understand the effects of DBR2 expression on the flow of artemisinic aldehyde into either artemisinin or arteannuin B, we determined the content of dihydroartemisinic aldehyde, artemisinin, artemisinic acid and arteannuin B content of A. annua varieties sorted into two chemotypes. The high artemisinin producers (HAPs), which includes the ‘2/39’, ‘Chongqing’ and ‘Anamed’ varieties, produce more artemisinin than arteannuin B; the low artemisinin producers (LAPs), which include the ‘Meise’, ‘Iran#8’, ‘Iran#14’, ‘Iran#24’ and ‘Iran#47’ varieties, produce more arteannuin B than artemisinin. Quantitative PCR showed that the relative expression of DBR2 was significantly higher in the HAP varieties. We cloned and sequenced the promoter of the DBR2 gene from varieties of both the LAP and the HAP groups. There were deletions/insertions in the region just upstream of the ATG start codon in the LAP varities, which might be the reason for the different promoter activities of the HAP and LAP varieties. The relevance of promoter variation, DBR2 expression levels and artemisinin biosynthesis capabilities are discussed and a selection method for HAP varieties with a DNA marker is suggested. Furthermore, putative cis-acting regulatory elements differ between the HAP and LAP varieties.
      PubDate: 2015-01-24
  • Identification and characterization of plant-specific NAC gene family in
           canola ( Brassica napus L.) reveal novel members involved in cell death
    • Abstract: Abstract NAC transcription factors are plant-specific and play important roles in plant development processes, response to biotic and abiotic cues and hormone signaling. However, to date, little is known about the NAC genes in canola (or oilseed rape, Brassica napus L.). In this study, a total of 60 NAC genes were identified from canola through a systematical analysis and mining of expressed sequence tags. Among these, the cDNA sequences of 41 NAC genes were successfully cloned. The translated protein sequences of canola NAC genes with the NAC genes from representative species were phylogenetically clustered into three major groups and multiple subgroups. The transcriptional activities of these BnaNAC proteins were assayed in yeast. In addition, by quantitative real-time RT-PCR, we further observed that some of these BnaNACs were regulated by different hormone stimuli or abiotic stresses. Interestingly, we successfully identified two novel BnaNACs, BnaNAC19 and BnaNAC82, which could elicit hypersensitive response-like cell death when expressed in Nicotiana benthamiana leaves, which was mediated by accumulation of reactive oxygen species. Overall, our work has laid a solid foundation for further characterization of this important NAC gene family in canola.
      PubDate: 2015-01-24
  • Positive selection drives neofunctionalization of the UbiA
           prenyltransferase gene family
    • Abstract: Abstract Gene duplication provides the key materials for new genes and novel functions. However, the mechanism underlying functional innovation remains unknown. In this study, we revealed the evolutionary pattern of the prenyltransferases of the UbiA gene family in 15 higher plants. Prenyltransferases of the UbiA gene family are involved in many important biological processes of both primary and secondary metabolism. Based on the phylogenetic relationships of the UbiA genes, seven subfamilies are classified. Confirming this classification, genes within each subfamily are characterized by similar exon numbers, exon lengths and patterns of motif combinations. Similar numbers of UbiA genes are found in different species within each subfamily except for Subfamily I, in which a Phaseoleae-specific expansion is detected in clade I-A. Homologous genes in clade I-A evolve rapidly, exchange sequences frequently and experience positive selection. Genes in clade I-A function as flavonoid prenyltransferase synthesis secondary compounds, while other genes from Subfamily I encode homogentisate phytyltransferase, which plays a role in primary metabolism. Thus, our results suggest that the secondary metabolism genes acquire new functions from those of primary metabolism through gene duplication and neofunctionalization driven by positive selection.
      PubDate: 2015-01-21
  • Arabidopsis thaliana MSI4/FVE associates with members of a novel family of
           plant specific PWWP/RRM domain proteins
    • Abstract: Abstract AtMSI4/FVE/ACG1, one of five Arabidopsis thaliana genes encoding MSI1-like proteins, helps determine plant growth and development (including control of flowering), as well as responses to certain biotic and abiotic stresses. We reasoned that the product of this gene, AtMSI4, acts through protein partners, which we have co-immunopurified with AtMSI4 from A. thaliana suspension culture cells and identified by liquid chromatography–mass spectrometry (LC–MS). Many of the proteins associated with AtMSI4 have distinct RNA recognition motif (RRM) domains, which we determined to be responsible for association with AtMSI4; and most of the associated RRM domain proteins also contain PWWP domains that are specific to plants. We propose these novel ATMSI4-associated proteins help form nucleoprotein complexes that determine pleiotropic functional properties of AtMSI4/FVE/ACG1 involving plant development and responses to stress.
      PubDate: 2015-01-20
  • Current status of viral expression systems in plants and perspectives for
           oral vaccines development
    • Abstract: Abstract During the last 25 years, the technology to produce recombinant vaccines in plant cells has evolved from modest proofs of the concept to viable technologies adopted by some companies due to significant improvements in the field. Viral-based expression strategies have importantly contributed to this success owing to high yields, short production time (which is in most cases free of tissue culture steps), and the implementation of confined processes for production under GMPs. Herein the distinct expression systems based on viral elements are analyzed. This review also presents the outlook on how these technologies have been successfully applied to the development of plant-based vaccines, some of them being in advanced stages of development. Perspectives on how viral expression systems could allow for the development of innovative oral vaccines constituted by minimally-processed plant biomass are discussed.
      PubDate: 2015-01-06
  • Overexpression of a cotton annexin gene, GhAnn1 , enhances drought and
           salt stress tolerance in transgenic cotton
    • Abstract: Abstract Plant annexins are members of a diverse, multigene protein family that has been associated with a variety of cellular processes and responses to abiotic stresses. GhAnn1, which encodes a putative annexin protein, was isolated from a cotton (Gossypium hirsutum L. acc 7235) cDNA library. Tissue-specific expression showed that GhAnn1 is expressed at differential levels in all tissues examined and strongly induced by various phytohormones and abiotic stress. In vivo and in vitro subcellular localization suggested that GhAnn1 is located in the plasma membrane. In response to drought and salt stress, transgenic cotton plants overexpressing GhAnn1 showed significantly higher germination rates, longer roots, and more vigorous growth than wild-type plants. In addition, plants overexpressing GhAnn1 had higher total chlorophyll content, lower lipid peroxidation levels, increased peroxidase activities, and higher levels of proline and soluble sugars, all of which contributed to increased salt and drought stress tolerance. However, transgenic cotton plants in which the expression of GhAnn1 was suppressed showed the opposite results compared to the overexpressing plants. These findings demonstrated that GhAnn1 plays an important role in the abiotic stress response, and that overexpression of GhAnn1 in transgenic cotton improves salt and drought tolerance.
      PubDate: 2015-01-01
  • Overexpression of heat stress-responsive TaMBF1c , a wheat ( Triticum
           aestivum L.) Multiprotein Bridging Factor, confers heat tolerance in both
           yeast and rice
    • Abstract: Abstract Previously, we found an ethylene-responsive transcriptional co-activator, which was significantly induced by heat stress (HS) in both thermo-sensitive and thermo-tolerant wheat. The corresponding ORF was isolated from wheat, and named TaMBF1c (Multiprotein Bridging Factor1c). The deduced amino acid sequence revealed the presence of conserved MBF1 and helix-turn-helix domains at the N- and C-terminus, respectively, which were highly similar to rice ERTCA (Ethylene Response Transcriptional Co-Activator) and Arabidopsis MBF1c. The promoter region of TaMBF1c contained three heat shock elements (HSEs) and other stress-responsive elements. There was no detectable mRNA of TaMBF1c under control conditions, but the transcript was rapidly and significantly induced by heat stress not only at the seedling stage, but also at the flowering stage. It was also slightly induced by drought and H2O2 stresses, as well as by application of the ethylene synthesis precursor ACC, but not, however, by circadian rhythm, salt, ABA or MeJA treatments. Under normal temperatures, TaMBF1c-eGFP protein showed predominant nuclear localization with some levels of cytosol localization in the bombarded onion epidermal cells, but it was mainly detected in the nucleus with almost no eGFP signals in cytosol when the bombarded onion cells were cultured under high temperature conditions. Overexpression of TaMBF1c in yeast imparted tolerance to heat stress compared to cells expressing the vector alone. Most importantly, transgenic rice plants engineered to overexpress TaMBF1c showed higher thermotolerance than control plants at both seedling and reproductive stages. In addition, transcript levels of six Heat Shock Protein and two Trehalose Phosphate Synthase genes were higher in TaMBF1c transgenic lines than in wild-type rice upon heat treatment. Collectively, the present data suggest that TaMBF1c plays a pivotal role in plant thermotolerance and holds promising possibilities for improving heat tolerance in crops.
      PubDate: 2015-01-01
  • Cloning and functional characterization of two abiotic stress-responsive
           Jerusalem artichoke ( Helianthus tuberosus ) fructan 1-exohydrolases
    • Abstract: Abstract Two fructan hydrolases were previously reported to exist in Jerusalem artichoke (Helianthus tuberosus) and one native fructan-β-fructosidase (1-FEH) was purified to homogeneity by SDS-PAGE, but no corresponding cDNA was cloned. Here, we cloned two full-length 1-FEH cDNA sequences from Jerusalem artichoke, named Ht1-FEH I and Ht1-FEH II, which showed high levels of identity with chicory 1-FEH I and 1-FEH II. Functional characterization of the corresponding recombinant proteins in Pichia pastoris X-33 demonstrated that both Ht1-FEHs had high levels of hydrolase activity towards β(2,1)-linked fructans, but low or no activity towards β(2,6)-linked levan and sucrose. Like other plant FEHs, the activities of the recombinant Ht1-FEHs were greatly inhibited by sucrose. Real-time quantitative PCR analysis showed that Ht1-FEH I transcripts accumulated to high levels in the developing leaves and stems of artichoke, whereas the expression levels of Ht1-FEH II increased in tubers during tuber sprouting, which implies that the two Ht1-FEHs play different roles. The levels of both Ht1-FEH I and II transcript were significantly increased in the stems of NaCl-treated plants. NaCl treatment also induced transcription of both Ht1-FEHs in the tubers, while PEG treatments slightly inhibited the expression of Ht1-FEH II in tubers. Analysis of sugar-metabolizing enzyme activities and carbohydrate concentration via HPLC showed that the enzyme activities of 1-FEHs were increased but the fructose content was decreased under NaCl and PEG treatments. Given that FEH hydrolyzes fructan to yield Fru, we discuss possible explanations for the inconsistency between 1-FEH activity and fructan dynamics in artichokes subjected to abiotic stress.
      PubDate: 2015-01-01
  • A SNP in OsMCA1 responding for a plant architecture defect by deactivation
           of bioactive GA in rice
    • Abstract: Abstract Plant architecture directly affects biomass in higher plants, especially grain yields in agricultural crops. In this study, we characterized a recessive mutant, plant architecture determinant (pad), derived from the Oryza sativa ssp. indica cultivar MH86. The mutant exhibited severe dwarf phenotypes, including shorter and stunted leaves, fewer secondary branches during both the vegetative and reproductive growth stages. Cytological studies revealed that pad mutant growth defects are primarily due to the inhibition of cell expansion. The PAD gene was isolated using a map-based cloning strategy. It encodes a plasma membrane protein OsMCA1 and a SNP responsible for a single amino acid change was found in the mutant. PAD was universally expressed in rice tissues from the vegetative to reproductive growth stages, especially in seedlings, nodes and rachillae. Quantitative real-time PCR analysis revealed that the most of the genes responding to gibberellin (GA) metabolism were up-regulated in pad mutant internodes. The endogenous GA content measurement revealed that the levels of GA1 were significantly decreased in the third internode of pad mutants. Moreover, a GA response assay suggested that OsMCA1/PAD might be involved in the regulation of GA metabolism and signal transduction. Our results revealed the pad is a loss-of-function mutant of the OsMCA1/PAD, leading to upregulation of genes related to GA deactivation, which decreased bioactive GA levels.
      PubDate: 2015-01-01
  • The wheat NHX antiporter gene TaNHX2 confers salt tolerance in transgenic
           alfalfa by increasing the retention capacity of intracellular potassium
    • Abstract: Abstract Previous studies have shown that TaNHX2 transgenic alfalfa (Medicago sativa L.) accumulated more K+ and less Na+ in leaves than did the wild-type plants. To investigate whether the increased K+ accumulation in transgenic plants is attributed to TaNHX2 gene expression and whether the compartmentalization of Na+ into vacuoles or the intracellular compartmentalization of potassium is the critical mechanism for TaNHX2-dependent salt tolerance in transgenic alfalfa, aerated hydroponic culture was performed under three different stress conditions: control condition (0.1 mM Na+ and 6 mM K+ inside culture solution), K+-sufficient salt stress (100 mM NaCl and 6 mM K+) and K+-insufficient salt stress (100 mM NaCl and 0.1 mM K+). The transgenic alfalfa plants had lower K+ efflux through specific K+ channels and higher K+ absorption through high-affinity K+ transporters than did the wild-type plants. Therefore, the transgenic plants had greater K+ contents and [K+]/[Na+] ratios in leaf tissue and cell sap. The intracellular compartmentalization of potassium is critical for TaNHX2-induced salt tolerance in transgenic alfalfa.
      PubDate: 2014-12-31
  • Cucumber ECERIFERUM1 ( CsCER1 ), which influences the cuticle properties
           and drought tolerance of cucumber, plays a key role in VLC alkanes
    • Abstract: Abstract Most land plants have a wax layer which covers their aerial parts to protect them from environmental stresses, such as drought, UV radiation, and pathogenic invasion. The wax biosynthesis has been well studied previously in Arabidopsis, but it still remains elusive in cucumber. Here, we isolated a CER1 homolog CsCER1 in cucumber, and we found that the expression of CsCER1 in the cucumber line 3401 which shows waxy fruit phenotype is much higher than that in the cucumber line 3413 which displays glossy fruit phenotype. Spatial and temporal expression analyses revealed that CsCER1 is specifically expressed in the epidermis where waxes are synthesized, and sub-cellular location showed that CsCER1 protein is localized to the endoplasmic reticulum. The expression of CsCER1 can be induced by low temperature, drought, salt stress and abscisic acid. In addition, abnormal expressions of CsCER1 in transgenic cucumber plants have dramatic effects on very-long-chain (VLC) alkanes biosynthesis, cuticle permeability, and drought resistance. Our data suggested that CsCER1 plays an important role in VLC alkanes biosynthesis in cucumber.
      PubDate: 2014-12-25
  • Over-expression of mouse ornithine decarboxylase gene under the control of
           fruit-specific promoter enhances fruit quality in tomato
    • Abstract: Abstract Diamine putrescine (Put) and polyamines; spermidine (Spd) and spermine (Spm) are essential component of every cell because of their involvement in the regulation of cell division, growth and development. The aim of this study is to enhance the levels of Put during fruit development and see its implications in ripening and quality of tomato fruits. Transgenic tomato plants over-expressing mouse ornithine decarboxylase gene under the control of fruit-specific promoter (2A11) were developed. Transgenic fruits exhibited enhanced levels of Put, Spd and Spm, with a concomitant reduction in ethylene levels, rate of respiration and physiological loss of water. Consequently such fruits displayed significant delay of on-vine ripening and prolonged shelf life over untransformed fruits. The activation of Put biosynthetic pathway at the onset of ripening in transgenic fruits is also consistent with the improvement of qualitative traits such as total soluble solids, titratable acids and total sugars. Such changes were associated with alteration in expression pattern of ripening specific genes. Transgenic fruits were also fortified with important nutraceuticals like lycopene, ascorbate and antioxidants. Therefore, these transgenic tomatoes would be useful for the improvement of tomato cultivars through breeding approaches.
      PubDate: 2014-12-24
  • Arabidopsis thaliana thymidine kinase 1a is ubiquitously expressed during
           development and contributes to confer tolerance to genotoxic stress
    • Abstract: Abstract Thymidine kinase catalyzes the first step in the nucleotide salvage pathway by transferring a phosphate group to a thymidine molecule. In mammals thymidine kinase supplies deoxyribonucleotides for DNA replication and DNA repair, and the expression of the gene is tightly regulated during the cell cycle. Although this gene is phylogenetically conserved in many taxa, its physiological function in plants remains unknown. The genome of the model plant Arabidopsis thaliana has two thymidine kinase genes (AtTK1a and AtTK1b) and microarray data suggest they might have redundant roles. In this study we analyzed the TK1a function by evaluating its expression pattern during development and in response to genotoxic stress. We also studied its role in DNA repair by the characterization of a mutant that contained the T-DNA insertion in the promoter region of the TK1a gene. We found that TK1a is expressed in most tissues during plant development and it was differentially induced by ultraviolet-C radiation because TK1b expression was unaffected. In the mutant, the T-DNA insertion caused a 40 % rise in transcript levels and enzyme activity in Arabidopsis seedlings compared to wild-type plants. This elevation was enough to confer tolerance to ultraviolet-C irradiation in dark conditions, as determined by root growth, and meristem length and structure. TK1a overexpression also provided tolerance to genotoxins that induce double-strand break. Our results suggest that thymidine kinase contributes to several DNA repair pathways by providing deoxythymidine triphosphate that serve as precursors for DNA repair and to balance deoxyribonucleotides pools.
      PubDate: 2014-12-24
  • The pearl millet mitogen-activated protein kinase PgMPK4 is involved in
           responses to downy mildew infection and in jasmonic- and salicylic
           acid-mediated defense
    • Abstract: Abstract Plant mitogen-activated protein kinases (MPKs) transduce signals required for the induction of immunity triggered by host recognition of pathogen-associated molecular patterns. We isolated a full-length cDNA of a group B MPK (PgMPK4) from pearl millet. Autophosphorylation assay of recombinant PgMPK4 produced in Escherichia coli confirmed it as a kinase. Differential accumulation of PgMPK4 mRNA and kinase activity was observed between pearl millet cultivars 852B and IP18292 in response to inoculation with the downy mildew oomycete pathogen Sclerospora graminicola. This increased accumulation of PgMPK4 mRNA, kinase activity as well as nuclear-localization of PgMPK protein(s) was only detected in the S. graminicola resistant cultivar IP18292 with a ~tenfold peak at 9 h post inoculation. In the susceptible cultivar 852B, PgMPK4 mRNA and immuno-detectable nuclear PgMPK could be induced by application of the chemical elicitor β-amino butyric acid, the non-pathogenic bacteria Pseudomonas fluorescens, or by the phytohormones jasmonic acid (JA) or salicylic acid (SA). Furthermore, kinase inhibitor treatments indicated that PgMPK4 is involved in the JA- and SA-mediated expression of three defense genes, lipoxygenase, catalase 3 and polygalacturonase-inhibitor protein. These findings indicate that PgMPK/s contribute to pearl millet defense against the downy mildew pathogen by activating the expression of defense proteins.
      PubDate: 2014-12-20
  • GsSKP21 , a Glycine soja S-phase kinase-associated protein, mediates the
           regulation of plant alkaline tolerance and ABA sensitivity
    • Abstract: Abstract Plant SKP1-like family proteins, components of the SCF complex E3 ligases, are involved in the regulation of plant development and stress responses. Little is known about the precise function of SKP genes in plant responses to environmental stresses. GsSKP21 was initially identified as a potential stress-responsive gene based on the transcriptome sequencing of Glycine soja. In this study, we found that GsSKP21 protein contains highly conserved SKP domains in its N terminus and an extra unidentified domain in its C terminus. The transcript abundance of GsSKP21, detected by quantitative real-time PCR, was induced under the treatment of alkali and salt stresses. Overexpression of GsSKP21 in Arabidopsis dramatically increased plant tolerance to alkali stress. Furthermore, we found that overexpression of GsSKP21 resulted in decreased ABA sensitivity during both the seed germination and early seedling growth stages. GsSKP21 mediated ABA signaling by altering the expression levels of the ABA signaling-related and ABA-induced genes. We also investigated the tissue expression specificity and subcellular localization of GsSKP21. These results suggest that GsSKP21 is important for plant tolerance to alkali stress and plays a critical regulatory role in the ABA-mediated stress response.
      PubDate: 2014-12-05
  • Effect of cytokinins on delaying petunia flower senescence: a
           transcriptome study approach
    • Abstract: Abstract Flower senescence is a fascinating natural process that represents the final developmental stage in the life of a flower. Plant hormones play an important role in regulating the timing of flower senescence. Ethylene is a trigger and usually accelerates the senescence rate, while cytokinins are known to delay it. The aim of this work was to study the effect of 6-benzylaminopurine (BA) on petal senescence by transcript profile comparison after 3 or 6 h using a cross-species method by hybridizing petunia samples to a 4 × 44 K Agilent tomato array. The relative content of ethylene, abscisic acid, anthocyanins, total carotenoids and total phenols that determine the physiological behaviours of the petal tissue were measured. BA treatment prolonged the flower life and increased the concentrations of phenols and anthocyanins, while total carotenoids did not increase and were lower than the control. The ethylene biosynthetic and perception gene expressions were studied immediately after treatment until 24 h and all genes were repressed, while ethylene production was strongly induced after 4 days. The microarray analyses highlighted that BA strongly affected gene regulation after 3 h, but only 14 % of genes remained differentially expressed after 6 h. The most affected pathways and genes were those related to stress, such as heat shock proteins, abscisic acid (ABA) catabolism and its signalling pathway, lipid metabolism and antioxidant defence systems. A gene annotation enrichment analysis using DAVID showed that the most important gene clusters were involved in energy generation and conservation processes. In addition to the ethylene pathway, cytokinins seem to be strongly involved the regulation of the ABA response in flower tissues.
      PubDate: 2014-11-26
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