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ABSTRACT: In this study, we compared interactions of two Melampsora foliar rust species with poplar, which resulted in either limited or abundant pathogen proliferation. In the pathosystem exhibiting limited pathogen growth, a defence response was observed after invasion of poplar leaf tissues by the biotroph, with late and clear production of reactive oxygen species (ROS) and other products. Characterisation of the histological, biochemical and transcriptional events occurring in both pathosystems showed striking similarity with components of plant defence reactions observed during qualitative resistance. Key components associated with development of an active defence response, such as up-regulation of pathogenesis-related (PR) genes, were observed during infection. Moreover, the time course and strength of gene induction appear to be critical determinants for the outcome of the tree-pathogen interaction. This work provides basic biochemical characterisation and expression data for the study of so-called partial resistance in the poplar-rust pathosystem, which is also applicable to other plant-pathogen interactions resulting in quantitative disease resistance.
Plant Biology 03/2010; 12(2):364-76. · 2.39 Impact Factor
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Revue Internationale de Géomatique. 01/2010; 20:363-389.
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ABSTRACT: In eastern Canada, the white pine weevil (Pissodes strobi Peck) is a pest of several native pine and spruce species and of the introduced species, Norway spruce (Picea abies Karst). We evaluated the feeding activities, oviposition and rate of adult emergence of white pine weevil on field-grown Norway spruce subjected to jasmonic acid or wounding pretreatments. We also monitored the host-plant reaction to white pine weevil attack, jasmonic acid and wounding treatments by quantifying several mono- and sesquiterpenes in bark and characterizing some molecular aspects of the terpenoid response. Two cDNA sequences were identified that had a high percentage of identity with genes encoding monoterpene or sesquiterpene synthases. Both putative terpene synthase genes showed distinctive profiles in Norway spruce bark and needles following all treatments. Although the Norway spruce trees showed different physiological responses to mechanical wounding and white pine weevil attack, transcript activity of the gene encoding terpenoid synthase and consequent accumulation of terpenoid resin did not significantly affect the weevils' feeding activities, oviposition or rate of adult emergence.
Tree Physiology 12/2006; 26(11):1377-89. · 2.88 Impact Factor
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ABSTRACT: The objective of the study was to demonstrate the importance of bark polar fraction from Norway spruce [Picea abies (L.) Karst.] terminal leaders on the feeding activity and oviposition process of the female white pine weevil, Pissodes strobi (Peck). The bark polar fraction was extracted with a ternary solvent [chloroform, methanol and water (12 : 5 : 3)]. This extracted fraction was added, at different concentrations, to an artificial diet on which mated female white pine weevils could feed and oviposit. The bark polar fraction of Norway spruce terminal leaders promoted white pine weevil oviposition compared with untreated artificial diet. The results of this study contributed to the development of an efficient artificial rearing substrate required to better understand the interactions between white pine weevil and its host plants. The importance of more specific compounds found in the polar fraction could eventually help produce more resistant trees.
Journal of Applied Entomology 05/2006; 130(5):284 - 289. · 1.31 Impact Factor
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ABSTRACT: Important losses in poplar productivity occur because of susceptibility to microbial pathogens. To enhance disease resistance in susceptible genotypes, the gene coding for D4E1, a synthetic antimicrobial peptide consisting of 17 amino acid residues, was introduced into poplar (Populus tremula L. x Populus alba L.) via Agrobacterium-mediated transformation. Four kanamycin-resistant transformants were selected based on significant accumulation of the D4E1 transcript and confirmed by reverse transcription-polymerase chain reaction and RNA dot-blot analysis. These transgenic poplar lines were tested for resistance to Agrobacterium tumefaciens, Xanthomonas populi pv. populi and Hypoxylon mammatum (Wahl.) Miller. One transgenic poplar line, Tr23, bearing the highest transcript accumulation for the D4E1 gene, showed a significant reduction in symptoms caused by A. tumefaciens and X. populi. However, none of the transgenic poplar lines showed a significant difference in disease response to the fungal pathogen H. mammatum.
Tree Physiology 05/2003; 23(6):405-11. · 2.88 Impact Factor
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ABSTRACT: As the commercial production of transgenic annual crops becomes a reality in many parts of the world, many people wonder if the genetic engineering of perennial trees will allow their eventual commercialization. Not long ago, trees were considered to be recalcitrant material for most molecular biology techniques, including genetic transformation. However, transgenes for shortening the juvenile phase or for phytoremediation purposes have now been incorporated, and the alteration of lignin biosynthesis and increased cellulose accumulation in forest trees have also been accomplished. For long-lived tree species, new questions arise regarding the stability of integration and expression of foreign genes. Biosafety considerations, including transgene dispersion through the pollen and advances in strategies to avoid this, are also important.
Trends in Biotechnology 01/2002; 19(12):500-6. · 9.15 Impact Factor
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ABSTRACT: To elucidate heterologous promoter function in gymnosperms, we introduced the bean phenylalanine ammonia-lyase-beta-glucuronidase (PAL2-GUS) gene fusion into white pine (Pinus strobus L.). Over 15 lines were produced and integration of Agrobacterium T-DNA was confirmed by Southern analysis. Induction of the reporter gene was detected in all of the lines tested following UV illumination. In contrast, a weak but constant induction was seen in only a few lines following treatment with salicylic acid (SA) or jasmonic acid (JA). However, pretreatment of suspension cultures with SA or JA enhanced the induction of PAL2-GUS expression by UV irradiation. This specific enhancement or potentiation was reduced by 50% by treating the cells with indomethacin, an inhibitor of phospholipase activity, suggesting that the observed potentiation of UV induction involves the octadecanoid pathway. The UV induction was completely abolished by treating the cells with okadaic acid, an inhibitor of phosphatase activity. Thus, the induction of the heterologous PAL2 promoter from bean is consistent with the induction of phenylalanine ammonia-lyase (PAL) in angiosperms. Furthermore, our findings suggest that conifers, although phylogenetically distant to angiosperms, share some conserved promoter elements and some signal transduction mechanisms for UV-light perception.
Tree Physiology 08/2001; 21(10):665-72. · 2.88 Impact Factor
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ABSTRACT: In ongoing investigations of the role of the signal transduction pathway in tree-pathogen interactions, four complete and two partial 14-3-3 cDNAs have been isolated which are members of a gene family. Comparisons of DNA sequences reveal a high degree of identity among the cDNAs, and, in some cases, higher than 75% sequence similarity with previously published sequences. Sequence analysis at the amino acid level uncovered potential phosphorylation sites, some of which were identical among the proteins, and some of which varied. Treatment of trees with chitosan, jasmonates or by wounding of leaves, caused increases in the levels of 14-3-3 mRNA transcripts. Since jasmonates and chitosan are signal transducers of defence reactions in plants, these results suggest a possible role for 14-3-3 proteins in the pathogen defence response of deciduous trees. Effects of elicitors on transcription of the pal gene were also monitored. Pal is a well-characterized, pathogen response-related gene.
Journal of Experimental Botany 07/2001; 52(359):1331-8. · 5.36 Impact Factor
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ABSTRACT: We have used the conservation of reverse transcriptase and integrase domains among retroelements to PCR-amplify three well-known types of these mobile genetic elements. Reverse transcriptase sequences from Ty1-copia were identified in spruce in this way, as well as integrase sequences from the Ty3-gypsy group. Using these sequences as probes against a Picea glauca genomic bank, individual members from the LTR (long terminal direct repeat) groups were obtained. A partial Ty1-copia-type element named Spcl was isolated along with a Ty3-gypsy-type element named Spdl. Genomic Southern hybridizations revealed the complexity and high copy number of LTR retrotransposons in black and white spruce.
Genome 01/2001; 43(6):1084-9. · 1.65 Impact Factor
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ABSTRACT: A cDNA encoding a 14-3-3 protein was isolated from white spruce. The corresponding polypeptide contains several motifs that
are conserved in this type of protein and is predicted to be 260 amino acids in length. Multiple banding in Southern blot
analysis suggests that the gene encoding this cDNA is, in fact, part of a small family of genes. Wounding and chitosan treatment
of spruce plants followed by Northern blot analysis indicates that these stimuli caused the accumulation of 14-3-3 mRNA. In
addition, cell suspension cultures treated with methyl jasmonate showed up-regulation of 14-3-3-encoding mRNA. Chitosan and
methyl jasmonate are both signalling molecules in the activation of plant defense response genes. Therefore, our results suggest
a possible role for this 14-3-3 protein in the pathogen defense response of coniferous trees.
Plant Cell Reports 12/2000; 20(1):79-84. · 2.27 Impact Factor
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ABSTRACT: The phenylpropanoid pathway has important functions in angiospermous plants following exposure to environmental stresses, such as wounding and pathogen attack, that lead to production of compounds including lignin, flavonoids and phytoalexins. Chalcone synthase (CHS) is a key enzyme in this pathway, catalyzing the first step in flavonoid biosynthesis, whose expression can be induced in response to environmental stress. To explore the response of conifers to environmental stress, expression of spruce CHS and its inducibility were investigated. A partial spruce CHS cDNA clone was isolated using PCR. Examination of the expression patterns of the CHS gene family in white spruce revealed accumulation of CHS mRNA in needle tissue following mechanical wounding, or application of signal molecules like jasmonic acid or methyl jasmonate. Repeated mechanical wounding or jasmonate applications had an enhancing effect on transcript accumulation in needles. A systemic accumulation of CHS mRNAs following wounding was also observed. Conifers thus appear to possess a general wound response similar to that found for angiosperms, which includes CHS induction as well as its inducibility by jasmonic acid and airborne methyl jasmonate.
Plant and Cell Physiology 09/2000; 41(8):982-7. · 4.70 Impact Factor
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ABSTRACT: Using particle bombardment of mature somatic embryos followed by the induction of secondary embryogenesis in the presence
of hygromycin, we produced over 90 lines of transgenic embryonal masses expressing β-glucuronidase from two genotypes of black
spruce. Transformation efficiencies of up to 7% (1 transgenic line per 14 embryos bombarded) were achieved by extending the
period of selection from 8 to 12 weeks. Proliferation of transformed embryonal masses in the presence of hygromycin had no
effect on either embryogenicity or embryo maturation. Southern blot hybridization and PCR amplification confirmed the presence
of the hygromycin phosphotransferase gene in genomic DNA. The expression of the β-glucuronidase gene in the needles of regenerated
seedlings support the potential for long-term transgene expression in spruce.
Plant Cell Reports 01/2000; 19(4):358-362. · 2.27 Impact Factor
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ABSTRACT: A presumably full-length cDNA encoding a putative glycine-rich RNA binding protein was isolated from a lambdaZAP cDNA library prepared from mRNAs extracted from needles of 2year old white spruce seedlings, which had been either wounded or jasmonate-treated. The cDNA, designated PgRNP (Picea glauca RNP protein), presents a 468bp open reading frame encoding a 155 amino acid protein. This polypeptide possesses an RNA binding domain (RNP-CS) and a glycine-rich domain. Comparative alignment reveals extensive homologies to glycine-rich RNA binding proteins containing an RNP-CS found in other angiosperm species. Genomic hybridization experiments suggest that the PgRNP gene is part of a small multigene family with at least four members. RNA blot analysis revealed that the PgRNP transcript is expressed in all tissues from non-stressed plants. Constitutive mRNA level was found in needle tissue from control as well as methyl-jasmonate treated plants. Wounding had no clear induction effect. Jasmonic acid treatment and systemic wound response had a positive effect on transcript accumulation. Transcript accumulation was slightly induced by cold in needles, and repressed by drought stress in both needle and root tissues of 2year old plants. Finally, the level of PgRNP accumulation was induced by wounding and repressed in 2week old dark-grown seedlings upon jasmonate treatments.
Gene 12/1999; 240(2):379-88. · 2.34 Impact Factor
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ABSTRACT: A genetic transformation procedure for white pine has been developed after cocultivation of embryogenic tissues with Agrobacterium tumefaciens. This efficient transformation procedure led to an average of four independent transformed lines per gram of cocultivated embryogenic tissue and up to 50 transformed lines can be obtained in a routine experiment. Constructs bearing the uidA gene or the green fluorescent protein (GFP) gene were introduced and -glucuronidase (GUS) activity was followed over time. The expression of the uidA gene was lowest with a 35S-gus-intron construct and was 20-fold higher with a 35S-35S-AMVgus::nptII construct. The addition of scaffold attachment region (SAR) sequences surrounding the gus::nptII fusion did not significantly enhance the GUS activity. Transformed mature somatic embryos have been germinated and plantlets are presently being acclimatized.
Molecular Breeding 09/1999; 5(5):429-440. · 2.85 Impact Factor
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ABSTRACT: Advances in elucidating the molecular processes controlling flower initiation and development have provided unique opportunities to investigate the developmental genetics of non-flowering plants. In addition to providing insights into the evolutionary aspects of seed plants, identification of genes regulating reproductive organ development in gymnosperms could help determine the level of homology with current models of flower induction and floral organ identity. Based upon this, we have searched for putative developmental regulators in conifers with amino acid sequence homology to MADS-box genes. PCR cloning using degenerate primers targeted to the MADS-box domain revealed the presence of over 27 MADS-box genes within black spruce (Picea mariana), including several with extensive homology to either AP1 or AGAMOUS, both known to regulate flower development in Arabidopsis. This indicates that like angiosperms, conifers contain a large and diverse MADS-box gene family that probably includes regulators of reproductive organ development. Confirmation of this was provided by the characterization of an AGAMOUS-like cDNA clone called SAG1, whose conservation of intron position and tissue-specific expression within reproductive organs indicate that it is a homologue of AGAMOUS. Functional homology with AGAMOUS was demonstrated by the ability of SAG1 to produce homeotic conversions of sepals to carpels and petals to stamens when ectopically expressed in transgenic Arabidopsis. This suggests that some of the genetic pathways controlling flower and cone development are homologous, and antedate the 300-million-year-old divergence of angiosperms and gymnosperms.
The Plant Journal 10/1998; 15(5):625-34. · 6.16 Impact Factor
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ABSTRACT: A study of the expression of a bean phenylalanine ammonia-lyase (PAL) promoter/beta-glucuronidase gene fusion in transgenic tobacco has shown that the PAL2 promoter has a modular organization. Expression of the PAL2 promoter in the vascular system involves positive and negative regulatory cis elements. Among these elements is an AC-rich motif implicated in xylem expression and a suppressing cis element for phloem expression. Using radiolabelled complementary oligonucleotides bearing the AC-rich motif, a cDNA clone encoding a DNA-binding protein has been isolated from a tobacco lambda gt11 expression library. This factor, named AC-rich binding factor (ACBF), showed binding specificity to the AC-rich region. The specificity of ACBF for the AC-rich region was also shown using a gel retardation assay with an ACBF recombinant protein extract. The deduced amino acid sequence from ACBF contains a long repeat of glutamine residues as found in well characterized transcription factors. Interestingly, ACBF shared sequence similarity to conserved amino acid motifs found in RNA-binding proteins. Genomic gel blot analysis indicated the presence of a small gene family of sequences related to ACBF within the tobacco nuclear genome. Analysis of tobacco mRNA using the ACBF cDNA as probe showed that while ACBF mRNA was present in all tissues examined, the highest transcript accumulation occurred in stem tissues. The functional characteristics of the AC-rich sequence were examined in transgenic tobacco. A heptamer of the AC-rich sequence, in front of a minimal 35S promoter from cauliflower mosaic virus (-46 to +4), conferred specific expression in xylem.
Plant Molecular Biology 11/1997; 35(3):281-91. · 4.15 Impact Factor
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Tree Physiology, v.26, 1377-1389 (2006).
