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PubMed2000

Architectural and physiological heterogeneity within the synflorescence of the pseudoviviparous grass Poa alpina var. vivipara L.

Many biotypes of the northern-hemisphere Arctic-Alpine grass Poa alpina L. reproduce asexually via prolification of the spikelet axis to produce dehiscing shoots. Although capable of photosynthesis, the source-sink characteristics of these synflorescence systems are unknown, including the degree to which plantlets from different regions of the synflorescence are capable of providing for their own carbon requirements, or contributing to other sinks. Photosynthetic rates within the paracladial zone, as determined by infrared gas analysis (IRGA), exceeded respiratory rates by 3-4-fold. (14)CO(2) tracer studies determined that the paracladial zone was not only as efficient at fixing carbon as the youngest fully expanded leaf (per unit dry weight), but that both organs exported carbon mainly basipetally (cf. extensive acropetal export from this leaf in seminiferous grasses). Distal plantlets of the paracladial zone fixed approximately 20% more (14)CO(2) than did proximal plantlets. This was by virtue of their greater dry weight. At dehiscence, 'distal' plantlets were more likely to become established, and possessed relative growth rates more than 10 times those of 'proximal' plantlets. Paracladial heterogeneity was also apparent as an increased proportion of aborted spikelets on proximal paracladia. The possible causes of this heterogeneity are discussed.

Carbon↗
PubMed2002

Role of sugars and organic acids in regulating the concentration and activity of the alternative oxidase in Poa annua roots.

Detached roots of Poa annua were used to study alternative oxidase protein expression upon the addition of sucrose, glucose, fructose, inositol, mannitol, citrate or malate, at a concentration of 1 or 10 mM for 24 h. After 24 h the capacity of cytochrome c oxidase was decreased equally in all treatments. Only citrate induced the expression of the alternative oxidase, especially at a concentration of 1 mM (15-fold). The activity of the alternative pathway (measured with the (18)O-fractionation technique) was not affected by the addition of sucrose for 24 h as compared with time zero. However, after the addition of citrate or mannitol the activity of the alternative pathway decreased to almost zero. The discrepancy between the large increase in alternative oxidase protein concentration when citrate was applied and the concomitant decrease in alternative pathway activity is discussed.

Carbohydrates↗
PubMed2000

Leifsonia poae gen. nov., sp. nov., isolated from nematode galls on Poa annua, and reclassification of 'Corynebacterium aquaticum' Leifson 1962 as Leifsonia aquatica (ex Leifson 1962) gen. nov., nom. rev., comb. nov. and Clavibacter xyli Davis et al. 1984 with two subspecies as Leifsonia xyli (Davis et al. 1984) gen. nov., comb. nov.

The new genus Leifsonia gen. nov. with two new species, Leifsonia poae sp. nov. (type strain VKM Ac-1401T) and Leifsonia aquatica (ex Leifson 1962) nom. rev., comb. nov. (the type species, with VKM Ac-1400T = DSM 20146T = JCM 1368T as type strain), is proposed to accommodate bacteria found in Poa annua root gall, induced by the nematode Subanguina radicicola, and 'Corynebacterium aquaticum' Leifson 1962. Further, it is proposed to reclassify Clavibacter xyli Davis et al. 1984 with two subspecies in the new genus as Leifsonia xyli (Davis et al. 1984) comb. nov., Leifsonia xyli subsp. xyli (Davis et al. 1984) comb. nov. and Leifsonia xyli subsp. cynodontis (Davis et al. 1984) comb. nov. Members of the proposed genus are characterized by coryneform morphology, peptidoglycans based upon 2,4-diaminobutyric acid, the major menaquinone MK-11, phosphatidylglycerol and diphosphatidylglycerol as principal phospholipids, the high content of anteiso- and iso-branched saturated fatty acids, and a DNA G+C base composition of 66-73 mol%. They form a distinct phylogenetic branch attached to the line of descent of Agromyces spp. The new and reclassified species of the new genus clearly differ from each other phylogenetically and phenetically and can be recognized by their morphologies, the cell wall sugar composition, the requirement of complex media for growth, and numerous physiological characteristics, including the oxidase reaction.

Actinomycetales↗
PubMed1992

Poa semilatent virus, a hordeivirus having no internal polydisperse poly(A) in the 3' non-coding region of the RNA genome.

RNA from the Hungarian isolate of poa semilatent virus (PSLV) directed in vitro synthesis of 120K, 75K, 25K (coat protein) and 20K polypeptides. In vitro translation of PSLV RNA was blocked by the cap analogue, m7Gpp, thus suggesting that the virus RNA was capped. PSLV RNA could be aminoacylated with [14C]tyrosine in vitro. The sequence of 1.5 kb from the 3' end of the PSLV RNA gamma component revealed two open reading frames (ORFs) separated by a uridine-rich intergenic region. The putative product of the incomplete 5'-proximal ORF showed a close amino acid sequence similarity with the C-terminal segment of the gamma a protein (putative RNA replicase) encoded in the barley stripe mosaic virus (BSMV) RNA gamma, and the 20K product of the 3'-proximal ORF was found to be related to the 17K gamma b product of BSMV. The sequence of 0.8 kb from the 3' end of PSLV RNA beta encompassed two (incomplete) overlapping ORFs whose putative products are related to the beta c and beta d proteins encoded in the similarly arranged ORFs of BSMV RNA beta. Nucleotide sequence homology between the respective parts of the two hordeivirus genomes was restricted to the ORF for gamma a, the spacer between the ORFs for gamma a and gamma b, and the 3' non-coding region, particularly the 95 nucleotide segment at the 3' end representing a tRNA-like structure. Despite limited sequence conservation beyond this segment, the entire 3' non-coding region of PSLV RNA could be folded in a tight pseudoknotted structure closely resembling that of BSMV RNA. Surprisingly, the 'signature' sequence typical for BSMV RNA, internal polydisperse poly(A) intercalated between the coding part of the 3' tRNA-like structure, was not detected in the PSLV genome. Instead, the virus RNA contained several oligoadenylate stretches spaced by other residues, close to the junction of its coding and 3' non-coding portions.

Amino Acid Sequence↗
PubMed2001

RNA-binding properties of the 63 kDa protein encoded by the triple gene block of poa semilatent hordeivirus.

The 63 kDa '63K' movement protein encoded by the triple gene block of poa semilatent virus (PSLV) comprises the C-terminal NTPase/helicase domain and the N-terminal extension domain, which contains two positively charged sequence motifs, A and B. In this study, the in vitro RNA-binding properties of PSLV 63K and its mutants were analysed. Membrane-immobilized 63K and N-63K (isolated N-terminal extension domain) bound RNA at high NaCl concentrations. In contrast, C-63K (isolated NTPase/helicase domain) was able to bind RNA only at NaCl concentrations of up to 50 mM. In gel-shift assays, C-63K bound RNA to form complexes that were unable to enter an agarose gel, whereas complexes formed by N-63K could enter the gel. Full-length 63K formed both types of complexes. Visualization of the RNA-protein complexes formed by 63K, N-63K and C-63K by atomic force microscopy demonstrated that each complex had a different shape. Collectively, these data indicate that 63K has two distinct RNA-binding activities associated with the NTPase/helicase domain and the N-terminal extension domain. Mutations in either of the positively charged sequence motifs A and B had little effect on the RNA binding of the N-terminal extension domain, whereas mutations in both motifs together inhibited RNA binding. Hybrid viruses with mutations in motifs A and B were able to infect inoculated leaves of Nicotiana benthamiana plants, but were unable to move systemically to uninoculated leaves, suggesting that the RNA-binding activity of the N-terminal extension domain of PSLV 63K is associated with virus long-distance movement.

Amino Acid Sequence↗
PubMed2002

Dual-colour imaging of membrane protein targeting directed by poa semilatent virus movement protein TGBp3 in plant and mammalian cells.

The movement function of poa semilatent hordeivirus (PSLV) is mediated by the triple gene block (TGB) proteins, of which two, TGBp2 and TGBp3, are membrane proteins. TGBp3 is localized to peripheral bodies in the vicinity of the plasma membrane and is able to re-direct TGBp2 from the endoplasmic reticulum (ER) to the peripheral bodies. For imaging of TGBp3-mediated protein targeting, PSLV TGBp3 tagged with a red fluorescent protein (DsRed) was used. Coexpression of DsRed-TGBp3 with GFP targeted to the ER lumen (ER-GFP) demonstrated that ER-GFP was contained in typical ER structures and peripheral bodies formed by TGBp3 protein, suggesting an ER origin for these bodies. In transient coexpression with viral membrane proteins tagged with GFP, DsRed-TGBp3 directed to the peripheral bodies the homologous TGBp2 protein and two unrelated membrane proteins, the 6 kDa movement protein of beet yellows closterovirus and the putative movement protein encoded by the genome component 4 of faba bean necrotic yellows nanovirus. However, coexpression of TGBp3 with GFP derivatives targeted to the ER membranes by artificial hydrophobic tail sequences suggested that targeting to the ER membranes per se was not sufficient for TGBp3-directed protein trafficking to peripheral bodies. TGBp3-induced targeting of TGBp2 also occurred in mammalian cells, indicating the universal nature of the protein trafficking signals and the cotargeting mechanism.

Animals↗
PubMed1968

Opposing Actions of Light in Seed Germination of Poa pratensis and Amaranthus arenicola.

Action spectra were measured for suppression of germination of Poa pratensis L. and Amaranthus arenicola I. M. Johnston seed under prolonged or continuous irradiation. The action maxima for both types of seeds are near 720 nm. The maxima are unchanged in position or magnitude in the presence of radiation in the region of 600 to 670 nm adequate to maintain phytochrome predominantly in the far-red-absorbing form. A reversible potentiation of germination to change in form of phytochrome was observed for both seeds. The bearing of these findings on a high-energy regulatory light response is discussed.

Journal Article↗
PubMed1980

Photomorphogenically Defined Light and Resistance of Poa pratensis to Drechslera sorokiniana.

Photomorphogenic light definitions were derived by mathematical determination of the estimated phytochrome photoequilibrium for each light treatment spectrum. A wide range of photomorphogenic light treatments represented by spectra with estimated phytochrome photoequilibria of 0.45, 0.54, 0.60, 0.67, and 0.71 was utilized to determine the influence of photomorphogenically defined light on resistance of Poa pratensis L. to pathogenesis by Drechslera sorokiniana. Accurate resolution of D. sorokiniana leaf spot development required evaluation of separate leaf ages due to the sequential appearance, development, and senescence of P. pratensis leaves. Disease development (all light treatments) was greatest on leaf 4 (oldest, postmature) followed by leaf 1 (youngest, premature). Low levels of disease occurred on leaves 2 and 3 (mature). Photomorphogenic light defined by estimated phytochrome photoequilibria greater than 0.60 (natural light approximately 0.60) was most disease promotive on leaf 1. Conversely, photomorphogenic light defined by estimated phytochrome photoequilibria of less than 0.60 was most disease promotive on leaf 4. These responses indicate that inherent resistance or susceptibility expressed by P. pratensis to pathogenesis by D. sorokiniana is regulated in part by leaf age (developmental senescent stage) and by photomorphogenically defined light quality. A hypothesis is presented and discussed which integrates and speculates on these observations with respect to the literature.

Journal Article↗
PubMed1984

Ethylene-Induced Chlorosis in the Pathogenesis of Bipolaris sorokiniana Leaf Spot of Poa pratensis.

Endogenous ethylene of Poa pratensis leaves infected by Bipolaris sorokiniana was evaluated as a factor in leaf chlorosis during pathogenesis. Detectable increases in endogenous ethylene of leaves of intact plants under normal ambient pressure occurred 12 hours after inoculation and was maximum at 48 hours; from 48 to 96 hours the ethylene progressively decreased. Necrotic lesions surrounded by chlorotic halos occurred on infected leaves between 24 and 48 hours. Midvein chlorosis interconnecting individual lesions and complete chlorosis of all tissues not directly affected by the lesions occurred between 72 and 96 hours, after maximum production of ethylene at 48 hours. The chlorophyll loss in infected leaves by 96 hours was 44% compared with controls.Subjecting inoculated leaves of intact plants to a controlled atmospheric-environmental system with an atmospheric pressure of 233 millibars and O(2) and CO(2) partial pressures adjusted to approximately that of normal ambient pressure during infection and disease development prevented most midvein chlorosis and complete chlorosis, but did not prevent necrotic lesion or chlorotic halo development. Under the hypobaric conditions, chlorophyll loss during disease development was reduced to 22% compared with controls at 96 hours. The observations suggest that ethylene may function late in pathogenesis of this host-pathogen interaction and is responsible for much of the chlorophyll loss after its maximum production at 48 hours.

Journal Article↗
PubMed1992

Group V allergens in grass pollens: IV. Similarities in amino acid compositions and NH2-terminal sequences of the group V allergens from Lolium perenne, Poa pratensis and Dactylis glomerata.

Monoclonal antibodies (PpV4) raised against Phleum pratense group V allergen were used for immuno-affinity chromatography of cross-reacting group V allergens from related grass species. Fractions enriched in group V allergen were obtained from Lolium perenne, Poa pratense and Dactylis glomerata extracts. The major components in these fractions were found in the Mwr range 25-28 kD. IgE binding to these components was shown using a pool of grass allergic sera, by SDS-PAGE immunoblotting. These fractions were electroblotted from tricine SDS-PAGE gels onto a polyvinylidene-difluoride membrane and selected group V bands were directly cut out and used for amino acid analysis and NH2-terminal sequencing. Both the amino acid compositions and the NH2-terminal sequences obtained for each group V allergen were almost similar to each other and to the sequence and composition of the previously described allergen Phl p V from Phleum pratense. A common trait of the investigated allergens, is the very high contents of alanine (25-32%) and the presence of the modified amino acid, hydroxyproline.

Allergens↗
PubMed1979

Nitrogen fixation associated with 'Park' Kentucky bluegrass (Poa pratensis L.).

Associative nitrogen fixation in Kentucky bluegrass (Poa pratensis L.) turfs inoculated with five nitrogen-fixing bacterial isolates was evaluated using the acetylene reduction assay and nitrogen accumulation as indicators of fixation. 'Park' and 'Nugget' Kentucky bluegrass turfs were grown in controlled environment chambers and inoculated with Klebsiella pneumoniae (W-2, W-6, and W-14), Erwinia herbicola (W-8), and Enterobacter cloacae (W-11). 'Park' inoculated with K. pneumoniae (W-6) had significant acetylene reduction activity using undisturbed turfs. Other treatments including turfs treated with heat-killed cells had no significant difference in acetylene reduction. In a second study, "Park' and 'South Dakota Certified' turfs were grown in a greenhouse and inoculated with K. pneumoniae (W-6) and E. herbicola (W-8). 'Park' inoculated with K. pneumoniae (W-6) had increased acetylene reduction activity rates and also a greater nitrogen accumulation in aerial tissues when compared to controls. Acetylene reduction activity was correlated (r = 0.92) to nitrogen accumulation. Other treatments did not effectively increase acetylene reduction activity or nitrogen accumulation.

Acetylene↗
PubMed1989

Relationship of lychnis ringspot virus to barley stripe mosaic virus and poa semilatent virus.

Barley stripe mosaic virus (BSMV), poa semilatent virus (PSLV), and lychnis ringspot virus (LRSV) have previously been assigned to the hordeivirus group because of similarities in their particle morphology, physicochemical properties and serological analyses. However, the serological relationships of the three viruses have not been determined by direct comparison. The present study evaluated the relatedness of these viruses by Western and dot immunoblotting and by nucleic acid hybridizations. Serological analyses of the coat proteins separated by gel electrophoresis and of intact virus particles bound to nitrocellulose membranes revealed that BSMV and PSLV are distantly related, but that they are more closely related to each other than to LRSV. The genomic RNAs of the viruses failed to cross-hybridize in northern hybridization tests conducted at different temperatures. These comparisons showed that BSMV, PSLV and LRSV are distinct viruses with little nucleotide sequence relatedness. Thus our data provide additional support for their inclusion as separate members of the hordeivirus group.

Antigens, Viral↗
PubMed1990

Isolation and characterization of a cDNA clone encoding an IgE-binding protein from Kentucky bluegrass (Poa pratensis) pollen.

We reported previously on the isolation and characterization of several allergens from Kentucky bluegrass (KBG) (Poa pratensis L.) pollen with the aid of the corresponding murine monoclonal antibodies (Mabs). In the present study, (1) an analysis of various tissues of this grass revealed that the allergenic components recognized by these Mabs were confined to the pollen; (2) intact translatable mRNA was isolated from the KBG pollen, and (3) a cDNA library was constructed with this mRNA in the lambda gt11 expression vector. Screening of this library with a pool of six sera from KBG-allergic patients, in combination with enzyme-labeled antibodies to human IgE, led to the isolation of a cDNA clone, referred to as KBG7.2. The nick-translated cDNA probe of KBG7.2 hybridized to a 1.5-kbp RNA transcript from KBG pollen. Moreover, transcripts corresponding to KBG7.2 were found in pollens of eight other grasses, indicating that the proteins similar to the one encoded by this cDNA may be present in these grasses. The nucleotide sequence of KBG7.2 was determined; interestingly, the corresponding derived amino acid sequence did not match any other sequence recorded in the protein data banks. The peptide encoded by KBG7.2 was expressed as a fusion protein utilizing the plasmid vector pWR590.1. Whereas none of the above allergen-specific Mabs bound to the fusion protein, all the 15 individual sera from grass pollen allergic patients recognized the fusion protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1992

Expression and thrombin cleavage of Poa p IX recombinant allergens fused to glutathione S-transferase.

The high-level expression and purification of Poa p IX recombinant grass pollen allergens were examined utilizing a modified pGEX plasmid, designated as pGEX 2T-1. This vector permits frame-1 ligation of lambda gt11 cDNA inserts and cleavage of the recombinant allergenic protein from the fusion partner glutathione S-transferase. The expression of the fusion proteins in water-soluble form varied among the transformants of the same bacterial strain and also between different host strains. Purification of the fusion proteins by affinity chromatography employing glutathione agarose gel revealed that proteases in the bacterial lysate bound to the gel and were co-eluted with the fusion proteins. These proteases, which specifically degraded the recombinant proteins to varying degrees, were inhibited by both of the inhibitors, phenylmethylsulfonyl fluoride and aprotinin. Cleavage by thrombin of the fusion proteins indicated that the structure of the individual protein affected the thrombin accessibility to the cleavage site. Increased concentration of thrombin partly compensated this effect, but resulted in a broader specificity of the enzyme. By contrast, cleavage of the fusion protein when it was still attached to the glutathione gel was convenient and led to purification of the product devoid of proteolytic activity. Since almost all the recombinant allergens have been cloned in lambda gt11 vector, the pGEX 2T-1 vector reported herein will facilitate the synthesis, purification of the corresponding allergenic proteins or their peptides in soluble and biologically active forms.

Allergens↗
PubMed1980

Purification and some properties of the main polymorphic form of acid phosphatase from Poa pratensis seeds.

The main polymorphic form of acid phosphatase was isolated from Poa pratensis seeds by chromatography on DEAE- and CM-cellulose and gel filtration on Bio-Gel P-100. The enzyme migrated as a single band in disc electrophoresis at pH 4.5 and 8.4. The purified enzyme is a glycoprotein of molecular weight about 33 000. Carbohydrate content accounts for 40% of the total weight. The optimum pH is at 5.2 and the apparent Km for p-nitrophenylphosphate, 0.55 mM. Fluoride ions are non-competitive and zinc ions-uncompetitive inhibitors, with the apparent Km values of 0.55 and 0.28 mM, respectively.

Acid Phosphatase↗
PubMed1984

High-dose cyclophosphamide and 5-fluorouracil versus vincristine, doxorubicin, and cyclophosphamide in advanced carcinoma of the breast. A phase III study of the Piedmont Oncology Association (POA).

Forty-nine patients with advanced carcinoma of the breast who had received no prior chemotherapy were randomized to receive either high-dose cyclophosphamide (C) 1250 mg/M2 intravenously on day 1 and 5-fluorouracil (F) 600 mg/M2 intravenously on days 1 through 5 (CF), or vincristine (V) 1.5 mg/M2, doxorubicin (A) 50 mg/M2 and cyclophosphamide (C) 500 mg/M2 (VAC), all intravenously on day 1. Both regimens were repeated at 3-week intervals. Nine of 25 patients (36%) treated with CF and ten of 21 patients (48%) treated with VAC showed a complete or partial response as defined by the (UICC) guidelines. The estimated median time to progression for all patients was 3.5 months for CF and 6.0 months for VAC, with the median time to progression for responding patients being 8.5 months on CF and 6.3 months on VAC. Estimated survival is also similar for the two regimens. Ten of the patients treated with high-dose CF experienced septic episodes and four died. Toxicity on the CF arm necessitated premature closure of the study, and thus full statistical comparison of the efficacy of the two regimens cannot be made.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1983

Vincristine, doxorubicin and mitomycin (VAM) in patients with advanced breast cancer previously treated with cyclophosphamide, methotrexate and fluorouracil (CMF). A clinical trial of the Piedmont Oncology Association (POA).

Thirty-six evaluable patients with advanced breast cancer who had failed prior CMF therapy [15 (42%) as adjuvant treatment and 21 (58%) for advanced disease] were treated with a combination of vincristine, doxorubicin, and mitomycin (VAM). There was one CR and 10 PR, giving a response rate of 31% (P, 95% confidence interval, 15%-47%). Response was not significantly related to age, performance status, disease-free interval, dominant site of disease, number of sites of disease, or estrogen receptor status. The median duration of response was 5 months for patients attaining CR or PR and 4.6 months for patients with stable disease. The median survival for patients with CR or PR of 7.9 months was not better than for those with stable disease (8.0 months), but both groups had significantly longer survival than those with initial progression. Patients who received VAM after failing adjuvant CMF had a 53% response rate (8 of 15), as against a 14% response rate (3 of 21) in those failing CMF for advanced disease (P less than 0.05). In spite of this difference, the survival distributions for these two groups were not significantly different. Myelosuppression was moderate and no cardiac toxicity was seen. The addition of mitomycin to vincristine and doxorubicin in previously treated patients does not appear to improve the results obtained with vincristine and doxorubicin alone.

Adult↗