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1.
Abstract Photosynthetic metabolism was investigated in leaves of five species of Flaveria (Asteraceac), all previously considered to be C4 plants. Leaves were exposed to 14CO2 for different intervals up to 16s. Extrapolation of 14C-product curves to zero time indicated that only F. trinervia and F.bidentis assimilated atmospheric CO2 exclusively through phosphoenolpyruvate carboxylase. The proportion of direct fixation of 14CO2 by ribulose-I, 5-bisphosphate carboxylase/oxygenase (Rubisco) ranged from 5 to 10% in leaves of F. australasica. F. palmeri and F. vaginata. Protoplasts of leaf mesophyll and bundle sheath cells were utilized to examine the intercellular compartmentation of principal photosynthetic enzymes. Leaves of F. australasica, F. palmeri and F. vaginata contained 5 to 7% of the leaf's Rubisco activity in the mesophyll cells, while leaves of F. trinervia and F. bidentis contained at most 0.2 to 0.8% of such activity in their mesophyll cells. Thus, F. trinervia and F. bidentis have the complete C4 syndrome, while F. australasica, F. palmeri and F. vaginata are less advanced, C4-like species. 相似文献
2.
Payant V; Abukashawa S; Sasseville M; Benkel BF; Hickey DA; David J 《Molecular biology and evolution》1988,5(5):560-567
Nuclear DNA was extracted from each of the eight species comprising the
Drosophila melanogaster species subgroup. Southern hybridization of this
DNA by using a molecular probe specific for the alpha-amylase coding region
showed that the duplicated structure of the amylase locus, first found in
D. melanogaster, is conserved among all species of the melanogaster
subgroup. Evidence is also presented for the concerted evolution of the
duplicated genes within each species. In addition, it is shown that the
glucose repression of amylase gene expression, which has been extensively
studied in D. melanogaster, is not confined to this species but occurs in
all eight members of the species subgroup. Thus, both the duplicated gene
structure and the glucose repression of Drosophila amylase gene activity
are stable over extended periods of evolutionary time.
相似文献
3.
THE LATE P. R. MASSALSKI J. I. COOPER C. U. T. HELLEN M. L. EDWARDS 《The Annals of applied biology》1988,112(3):415-426
The rates of germ tube elongation in vitro of pollen from cherry leaf roll virus (CLRV)-infected birch (Betula pendula) did not differ significantly from those of pollen from virus-free trees. Differences in percentage germination of pollen collected from trees at different sites were significant but percentages of germination of pollen from virus-infected and virus-free trees did not differ greatly from one another. In vivo, pollen from infected trees germinated on healthy and CLRV-infected stigmas and callose plugs formed in both types of tissues. However, the extent of callose plug formation was greater in the pollen tubes of virus-free grains germinating in infected stigmas than in reciprocal crosses. CLRV coat antigen was detected by ELISA in stigmatic tissue, from healthy trees, on which virus-carrying pollen grains had germinated. Using fluorescein isothiocyanate conjugated to CLRV-specific γ-globulin, viral coat antigen was detected throughout germ tubes from virus-carrying but not virus-free pollen germinating in vitro. Protoplasts released following Driselase digestion of pollen germ tubes from virus-infected trees contained CLRV antigen detectable by ELISA. During germination of virus-infected pollen there was little synthesis of viral coat protein or nucleic acid but, following inoculation with purified virus particles, protoplasts made from healthy germinating pollen produced increasing amounts of CLRV-specific antigen implying that CLRV replicated in this system. 相似文献
4.
A late Wenlock flora from Co. Tipperary, Ireland 总被引:1,自引:0,他引:1
D. EDWARDS F.L.S. J. FEEHAN D. G. SMITH 《Botanical journal of the Linnean Society. Linnean Society of London》1983,86(1-2):19-36
An assemblage of macroplants preserved as highly coalified compressions which lack anatomy is described from a Wenlock locality in County Tipperary, Ireland. Most of the fertile specimens are assigned to Cooksonia Lang. The taxonomic status of this genus is discussed. Some poorly preserved palynomorphs, including miospores, acritarchs, chitinozoans and a variety of tubes, have been isolated from associated sediments, but the age of the flora is based on graptolites. Sedimentological and palaeontological studies of the region are summarized. They provide little direct evidence for the habitats of the plants which are considered to have been terrestrial. The relevance of this flora to the current debate on the colonization of the land is evaluated and it is concluded that these plants provide the earliest record of erect fertile land plants of possible pteridophyte affinity. 相似文献
5.
SUMMARY.
- 1 The importance of bacteria in the diet of deposit-feeding mayflies (Stenonema spp.) from the Ogeecnee River, a sixth order low-gradient blackwater river in Georgia, U.S.A., was determined. Stenonema are abundant and productive on snags in biackwater rivers in the southeastern Coastal Plain of the U.S.A. Bacteria are abundant in the seston in this river, and are a potentially important food source.
- 2 Naturally occurring seston was fed to Stenonema larvae after bacterial DNA in the seston was labelled with methyl-[3H]thymidine. Larval respiration measurements and growth rate estimations were used to compare the amount of bacterial carbon assimilated and retained in larval tissue to the carbon requirements of the larvae.
- 3 Stenonema larvae incorporated 8.7×107±1.3×107 bacteria larva?1 h?1 This was equivalent to 93±6% of their daily growth, and 47±3% of their total daily carbon needs. Larger larvae incorporated more bacterial biomass, but mass specific incorporation was not related to size. Ingestion of bacteria while eating seston accumulated on snags appears to be an important component of the diet of Stenonema larvae in these rivers.
6.
JOÃO BATISTA TAVARES DA SILVA ISAAC ROITMAN 《The Journal of eukaryotic microbiology》1990,37(6):521-523
ABSTRACT. Three strains of Phytomonas serpens two from tomatoes, Lycopersicon esculentum one from the insect Phtia picta (Hemiptera, Coreidae), were cultivated in a chemically defined medium developed from a defined medium for cultivating insect flagellates. Besides organic growth factors required by other insect trypanosomatids this flagellate requires, serine and inositol. Glutamine stimulates growth, and, surprisingly, does not require heme. 相似文献
7.
MARC J. FAZIO ALBA C. DA SILVA THOM K. ROSIERE G. BENJAMIN BOUCK 《The Journal of eukaryotic microbiology》1995,42(5):570-580
ABSTRACT. Proteins of the membrane skeleton of Euglena gracilis were extensively phosphorylated in vivo and in vitro after incubation with [32 P]-orthophosphate or γ-[32 P] ATP. Endogenous protein threonine/serine activity phosphorylated the major membrane skeletal proteins (articulins) and the putative integral membrane protein (IP39) anchor for articulins. The latter was also the major target for endogenous protein tyrosine kinase activity. A cytoplasmic domain of IP39 was specifically phosphorylated, and removal of this domain with papain eliminated the radiolabeled phosphoamino acids and eliminated or radically shifted the PI of the multiple isoforms of IP39. In gel kinase assays IP39 autophosphorylated and a 25 kDa protein which does not autophosphorylate was identified as a threonine/serine (casein) kinase. Plasma membranes from the membrane skeletal protein complex contained threonine/serine (casein) kinase activity, and cross-linking experiments suggested that IP39 was the likely source for this membrane activity. pH optima, cation requirements and heparin sensitivity of the detergent solubilized membrane activity were determined. Together these results suggest that protein kinases may be important modulators of protein assembly and function of the membrane skeleton of these protistan cells. 相似文献
8.
9.
Borrelia burgdorferi is a spirochete pathogen transmitted among warm-
blooded hosts by ixodid ticks. Frequency-dependent selection for variant
outer-surface proteins might be expected to arise in this species, since
rare variants are more likely to avoid immune surveillance in previously
infected hosts. We sequenced the OspA and OspB genes of nine North American
strains and compared them with nine strains previously described. For each
gene, the mean number of synonymous substitutions per synonymous site and
the mean number of nonsynonymous substitutions per nonsynonymous site show
only a twofold excess of silent mutations. Synonymous rates vary widely
along the OspB protein. Some regions show a significant excess of silent
substitutions, while divergence in other regions is constrained by biased
base composition or selection. The presence, in antigenically important
regions of the protein, of significant variation among strains, as well as
evidence for recombination among strains, should be considered in attempts
to develop vaccines against this disease.
相似文献
10.
M P ROBINSON G BUTCHER R H CURTIS K G DA VIES K EVANS 《The Annals of applied biology》1993,123(2):337-347
Two monoclonal antibodies, which differentially recognise the two species of potato cyst nematodes (PCN), Globodera pallida and G. rostochiensis, are described. They have been shown to have potential for quantification of these two species, recognising proteins of the same molecular weight (34 kD) in both species. Further investigation showed these proteins to have isoelectric points at pH values of 5.7 in G. pallida and 5.9 in G. rostochiensis, in common with the proteins used by Fleming & Marks (1983) to differentiate the species of PCN. They are likely to be structurally very similar, with the same physiological function (and therefore similar concentrations) in the two species. In cross-reactivity tests with a wide range of soil nematode species, the antibodies reacted strongly only with species of the genus Globodera, and thereby confirmed their potential as the basis of a quantitative immunoassay likely to be useful in management of PCN populations. 相似文献