Demonstration of nucleomorph-encoded eukaryotic small subunit ribosomal RNA in cryptomonads

Summary In cryptomonads, unicellular phototrophic flagellates, the plastid(s) is (are) located in a special narrow compartment which is bordered by two membranes; it harbours neither mitochondria nor Golgi dictyosomes but comprises eukaryotic ribosomes and starch grains together with a small organelle called the nucleomorph. The nucleomorph contains DNA and is surrounded by a double membrane with pores. It is thought to be the vestigial nucleus of a phototrophic eukaryotic endosymbiont. Cryptomonads are therefore supposed to represent an intermediate state in the evolution of complex plastids from endosymbionts. We have succeeded in isolating pure nucleomorph fractions, and can thus provide, using pulsed field gel electrophoresis, polymerase chain reaction and sequence analysis, definitive proof for the eukaryotic nature of the symbiont and its phylogenetic origin.     

Protein Targeting into the Complex Plastid of Cryptophytes

The cryptophyte Guillardia theta harbors a plastid surrounded by four membranes. This turns protein targeting of nucleus-encoded endosymbiont localized proteins into quite a challenge, as the respective precursors have to pass either all four membranes to reach the plastid stroma or only the outermost two membranes to enter the periplastidal compartment. Therefore two sets of nuclear-encoded proteins imported into the endosymbiont can be distinguished and their topogenic signals may serve as good indicators for studying protein targeting and subsequent transport across the outermost membranes of the cryptophyte plastid. We isolated genes encoding enzymes involved in two different biochemical pathways, both of which are predicted to be localized inside the periplastidal compartment, and compared their topogenic signals to those of precursor proteins for the plastid stroma, which are encoded on either the nucleus or the nucleomorph. By this and exemplary in vitro and in vivo analyses of the topogenic signal of one protein localized in the periplastidal compartment, we present new data implicating the mechanism of targeting and transport of proteins to and across the outermost plastid membranes. Furthermore, we demonstrate that one single, but conserved amino acid is the triggering key for the discrimination between nucleus-encoded plastid and periplastidal proteins. [Reviewing Editor: Dr. Yves Van de Peer]     

An ultrastructural comparison betweenSpermatozopsis andDunaliella (Chlorophyceae)

The ultrastructure of the type species of the genusDunaliella, D. salina, has been reinvestigated in an attempt to clarify the relationships betweenDunaliella andSpermatozopsis. Dunaliella salina differs in the following ultrastructural characters fromSpermatozopsis (as exemplified byS. similis Preisig etMelkonian): presence of a distinctive surface coat covering the plasmalemma; presence of a prominent pyrenoid (with pairs of thylakoids partially entering the pyrenoid matrix); dictyosomes parabasal; endoplasmic reticulum closely underlying the plasmalemma around most of the cell; contractile vacuoles absent; cell form ovoid to elongated and not spirally twisted; mitochondrial profiles near the flagellar apparatus. Differences in the ultrastructure of the flagellar apparatus: basal body angle more or less fixed; distal connecting fibre cross-striated; system II fibre (rhizoplast) present, associated with mitochondrial profile; system I fibre underlying two-stranded microtubular root; mating structure present. These ultrastructural differences justify distinction between the two taxa at generic level. The problematical status of freshwater species ofDunaliella is briefly discussed.     

On the occurrence of twisted fibrillar structures in the cytoplasm of the red algaAlsidium helminthochorton (La Tourette) Kütz., ultrastructural and cytochemical observations

Summary The cytoplasm ofAlsidium cells contains unusual structures showing various fibrillar arrangements, either stacked rows of arcs or parallel fibrils in longitudinal view alternating with fibrils in cross-section. These regions, located exclusively in the cytoplasmic matrix, are highly proteinaceous and do not seem to be complexed with polysaccharides. Tilting observations under the electron microscope show that the appearance of arcs is an illusion and that the pattern fits the explanation given byBouligand and collaborators for various twisted biological structures.     

Mitochondrial DNA phylogeography of red deer (Cervus elaphus)

In order to understand the origin, phylogeny, and phylogeography of the species Cervus elaphus, we examined the DNA sequence variation of the mitochondrial cytochrome b gene of 51 populations of deer from the entire distribution area of Cervinae with an emphasis on Europe and Asia. Several methods, including maximum parsimony, maximum likelihood, and nested clade analysis, revealed that red deer originated from the area between Kyrgyzstan and Northern India. We found two distinct groups of red deer: a western group consisting of four subgroups and an eastern group consisting of three subgroups. Our mtDNA data do not support the traditional classification of red deer as only one species nor its division into numerous subspecies. The discrepancies between the geographical pattern of differentiation based on mtDNA cytochrome b and the existing specific and subspecific taxonomy based on morphology are discussed.     

Paraveinal mesophyll: Review and survey of the subtribeErythrininae (Phaseoleae,Papilionoideae, Leguminosae)

Paraveinal mesophyll (PVM) is a distinctive anatomical feature of the leaf mesophyll of some plant taxa that may represent a specialized physiological compartment. A comprehensive review of the 42 published references that mention PVM or similar cell layers and a survey of 121 of the 272 species of all nine genera of thePhaseoleae subtribeErythrininae demonstrate that PVM is nearly exclusively found inLeguminosae. InLeguminosae, PVM is either rare or absent in subfamilyCaesalpinioideae, uncommon inMimosoideae, and extensively distributed amongPapilionoideae. In subtribeErythrininae, PVM is ubiquitous inErythrina, and occurs in four other genera. ThreeErythrininae genera (Apios, Mucuna, andCochlianthus) lack PVM. Unique chloroplast-poor, enlarged conical cells (pellucid palisade idioblasts) occur in 80 species ofErythrina but not in any other genus ofErythrininae.     

Interspecific interactions between wild pygmy chimpanzees (Pan paniscus) and red colobus (Colobus badius)

Interspecific interactions accompanied by physical contacts between wild pygmy chimpanzees (Pan paniscus) and red colobus (Colobus badius) were observed on three occasions at Wamba, Republic of Zaire. In all cases, the red colobus initiated the interactions by approaching the pygmy chimpanzees. Most of the pygmy chimpanzees, which were within 5 m of the red colobus, were juveniles or infants but the adult male pygmy chimpanzees never showed any interest in the red colobus. The red colobus groomed the chimpanzees in two cases, but the latter never groomed the former. No true aggressive interactions were observed between the two species. The lack of any evidence of hunting of red colobus through longitudinal studies of the pygmy chimpanzees of Wamba, together with the present observations, suggests that red colobus are probably not targets of hunting by the pygmy chimpanzees.     

Flavonoid chemistry ofPolygonum sect.Tovara (Polygonaceae): A systematic survey

Polygonum sect.Tovara includes three controversial species;P. virginianum, P. filiforme, andP. neofiliforme. The flavonoid chemistry of these was examined to provide additional information on their delimitation and levels of differentiation. Eight flavonoid compounds were isolated and identified, all of which were 3-O-glycosides of the flavonols kaempferol, quercetin, and myricetin, and their acylated derivatives. Although they exhibit relatively simple flavonoid profiles, the three taxa are readily distinguished by their flavonoid constituents. In addition, they show fundamental differences in flavonol types and glycosylation patterns. These results, in conjunction with evidence from the morphology, strongly suggest thatP. virginianum, P. filiforme, andP. neofiliforme are closely allied but distinct species.     

A survey of C-band patterns in chromosomes ofLilium (Liliaceae)

C-band patterns are described for 20Lilium spp. distributed across six sections. All species have a similar basic karyotype (n = 12) but C-bands differ markedly between them. The patterns are characterized by a dispersed scattering of thin intercalary bands as well as centric and NOR bands. Only one species,L. canadense, shows a clear equilocal pattern with intercalary C-bands occurring proximally in all of the longer chromosome arms. Comparing species, similar patterns are revealed forL. regale andL. sulphureum, forL. formosanum andL. longiflorum (all in sect.Leucolirion) and to a lesser extent forL. hansonii, L. martagon, andL. tsingtauense (sect.Martagon). The pattern forL. henryi (previously classed in sect.Sinomartagon) matches those ofL. regale andL. sulphureum quite well and its transfer to sect.Leucolirion is proposed. This is consistent with results from interspecies hybrids betweenL. henryi andL. regale (and related species) which are reportedly fertile. No other clear similarities in C-band patterns were seen across species. It seems that C-band patterns change rapidly inLilium and hence their usefulness in classification will be restricted to identifying closely related species.Dedicated to Prof.D. G. Catcheside on the 80th anniversary of his birth.     

Epiphytic cyanophytes Xenococcus kerneri and Chamaesiphon minutus on the freshwater red alga Paralemanea catenata (Rhodophyta)

Epiphytes of Paralemanea catenata (Kützing) Vis & Sheath (Rhodophyta) were studied on material from the River Dyje in National Park Podyjí. Longitudinal sections of the thalli were made with help of Cryo Cut Microtome techniques. The epiphytic cyanophytes Xenococcus kerneri Hansgirg and Chamaesiphon minutus (Rostafinski) Lemmermann were recognized on the cortex of the thalli. Our observations of the determined species are discussed.     

N2 fixation by red alder (Alnus rubra) and scotch broom (Cytisus scoparius) planted under precommerically thinned Douglas-fir (Pseudotsuga menziesii)

Summary From acetylene reduction assays over a 10-month period starting in April 1979, nodule activities averaged 18.78 (se 4.67) moles C₂H₄ g nodule dw^–1 h^–1 forAlnus rubra and 59.95 (se 12.14) moles C₂H₄ g nodule dw^–1 h^–1 forCytisus scorparius. Plant rates were 1.91 (se. 47) moles C₂H₄ plant^–1 h^–1 forA. rubra and 0.55 (se. 17) moles C₂H₄ plant^–1 h^–1 forC. Scoparius. Plant activity and total leaf N were strongly correlated with the dw of other plant parts, but nodule activity and percent leaf N were not. Plant and nodule activities were not associated with temperature, moisture stress, precipitation events or percent light for either species over the growing season nor for 54A. rubra sampled in mid-season 1979 on one replication. After 5 to 6 growing seasons, 14A. rubra on the same site ranged from 30 to 332 cm in height and showed strong correlation between nodule dw, leaf dw, plant size and total leaf N. Results from this study and others indicate logistic equations may be modified to predict the effect of adding a N₂ fixing plant to a population of non N₂ fixing trees.     

Pilot survey of avahi population (woolly lemurs) in littoral forest fragments of southeast Madagascar

This study presents a pilot survey of the avahis (pair-living, nocturnal prosimians) living in threatened littoral forest fragments of southeastern Madagascar. In the period of October–December 2004, I evaluated the density of adult and newborn avahis (carried by the mothers) by counting the individuals encountered during 58 night walks in seven fragments of Sainte Luce and Mandena forests, along one trail/fragment. Along each trail, I used random plots (5 m²) for a preliminary characterization of the vegetation. The density of the population was not correlated with fragment size and number of plant morphospecies, while it was correlated with large tree availability. Possibly due to a low energy diet based on leaves and to specialized and energetically expensive vertical leaping, the loss of large trees by selective logging seems to affect avahi populations more than other variables.     

Prevalence of coccidia parasites (Protozoa) in red squirrels ( Sciurus vulgaris): effects of host phenotype and environmental factors

We investigated the relative importance of environmental factors versus host phenotype in determining parasite prevalence in Eurasian red squirrels ( Sciurus vulgaris). One hundred and forty-three fecal samples of 116 different squirrels collected in 2000 and 2001 from five study areas in the Italian Alps, were examined for intestinal protozoans. Two species of Eimeria were present with a medium to high prevalence in both years and in all areas, while two other species were rare, occurring only in some areas and not in all years. Cryptosporidium parvum had a high prevalence in the two study areas of the Western Alps, while in the three areas of the Central Alps it was recorded only once. The prevalence of Eimeria sciurorum and C. parvum fluctuated in parallel with squirrel density, suggesting a possible correlation between the presence of these protozoans and host density. A gender effect on E. sciurorum prevalence at low density could be explained by different space use patterns and social organization of males and females. C. parvum occurred more frequently in young squirrels, suggesting an acquired immunity in adults, but age-related susceptibility was not found for eimerian species. The coccidian community was more similar within than between regions, and study area and year were key parameters in predicting coccidia infection. There was no evidence of competition between coccidian species, but one positive interaction between E. sciurorum and E. andrewsi was observed. Our results suggest that the effects of geographic region, area features, and year effects probably related to fluctuations in host population density, were more important than individual phenotypic host characteristics in structuring the coccidian assemblage and determining levels of parasite prevalence in red squirrel populations.     

Putative tumor suppressor Lats2 induces apoptosis through downregulation of Bcl-2 and Bcl-x(L)

Lats2, also known as Kpm, is the second mammalian member of the novel Lats tumor suppressor gene family. Recent studies have demonstrated that Lats2 negatively regulates the cell cycle by controlling G1/S and/or G2/M transition. To further understand the role of Lats2 in the control of human cancer development, we have expressed the protein in human lung cancer cells by transduction of a replication-deficient adenovirus expressing human Lats2 (Ad-Lats2). Using a variety of techniques, including Annexin V uptake, cleavage of PARP, and DNA laddering, we have demonstrated that the ectopic expression of human Lats2 induced apoptosis in two lung cancer cell lines, A549 and H1299. Caspases-3, 7, 8, and 9 were processed in the Ad-Lats2-transduced cells; however, it was active caspase-9, not caspase-8, that initiated the caspase cascade. Inhibitors specific to caspase-3 and 9 delayed the onset of Lats2-mediated apoptosis. Western blot analysis revealed that anti-apoptotic proteins, BCL-2 and BCL-x(L), but not the pro-apoptotic protein, BAX, were downregulated in Ad-Lats2-transduced human lung cancer cells. Overexpression of either Bcl-2 or Bcl-x(L) in these cells lead to the suppression of Lats2-mediated caspase cleavage and apoptosis. These results show that Lats2 induces apoptosis through downregulating anti-apoptotic proteins, BCL-2 and BCL-x(L), in human lung cancer cells.     

Fish embryo culture: Migration and spreading of zebrafish (Brachydanio rerio) pigmented retinal epithelium

Summary Blastoderm explants fromBrachydanio rerio (Teleostei: Cyprinidae) high blastulas exhibited limited differentiation of optic structures in culture. A number of explants showed migration of pigmented retinal epithelial cells and formation of monolayers. The findings permit comparative studies in vitro on phenomena pertaining to pigmented retinal epithelial cell morphology, function, and differentiation. This investigation was supported by a grant from the Natural Sciences and Engineering Research Council of Canada.     

Gracilaria conferta and its epiphytes: (2) Interrelationship between the red seaweed and Ulva cf. lactuca

Ulva cf. lactuca has been a disturbing competitor of experimental Gracilaria conferta outdoor cultures in Israel. The effect of environmental conditions on the competitive ability of Ulva versus Gracilaria, and the main limiting factors for which these seaweeds compete, were studied here. Single and biculture experiments of both seaweeds showed that Ulva outgrew and damaged Gracilaria under all irradiance and temperature combinations. The higher competitive ability of Ulva cf. lactuca in bicultures was not a result of responses to shading or nitrogen shortage, but rather to a shortage of available inorganic carbon, an increase in pH and apparent excretions of Ulva which inhibited the growth of Gracilaria.     

Mycoses in red snapper (Lutjanus campechanus) caused by two deuteromycete fungi (Penicillium corylophilum and Cladosporium sphaerospermum)*

We report two species of deuteromycete fungi (Penicillium corylophilum and Cladosporium sphaerospermum) concurrently infecting the swim bladder and posterior kidney and causing erratic behavior in two specimens of wild-caught, tank-held red snapper (Lutjanus campechanus). Lesions produced by both species infiltrated the immediately surrounding tissue and produced severe pathological changes; however, the infection apparently was not systemic. Only P. corylophilum grew in the initial culture from the swim bladder and only C. sphaerospermum grew in the initial culture from the kidney. Infection may have occurred upon penetration of a syringe to deflate the swim bladder. There was no horizontal transmission to 13 other specimens of red snapper held in the same tank. This suggests that these fungi are not primary pathogens. Injection of each species into various sites in the Gulf killifish, Fundulus grandis, failed to produce infections within 1 month, suggesting differences in susceptibility among species.     

Characterization of expressed pigmented core light harvesting complex (LH 1) in a reaction center deficient mutant of Blastochloris viridis

The utility of photosynthetically defective mutants in the purple photosynthetic bacterium Blastochloris viridis (formerly Rhodopseudomonas viridis)was demonstrated with construction of a reaction-center deficient mutant, LH 1-H. This LH 1-H mutant has a photosynthetic apparatus in which most of the puf operon genes were deleted, resulting in an organism containing only the genes for the light harvesting polypeptides and the H subunit of the reaction center. This B. viridisstrain containing a truncation of the puf operon was characterized by gel electrophoresis, lipid-to-protein ratio analysis, optical spectroscopy, electron paramagnetic resonance and transmission electron microscopy. Optical and electron paramagnetic resonance spectroscopies revealed no photoactivity in this LH 1-H mutant consistent with the absence of intact reaction centers. Electron paramagnetic resonance evidence for assembled LH 1 complexes suggested that the interactions between light harvesting polypeptide complexes in membranes were largely unchanged despite the absence of their companion reaction center cores. The observed increase in the lipid-to-protein ratio was consistent with modified interactions between LH 1s, a view supported by transmission electron microscopy analysis of membrane fragments. The results show that B. viridis can serve as a practical system for investigating structure-function relationships in membranes and photosynthesis through the construction of photosynthetically defective mutants. This revised version was published online in August 2006 with corrections to the Cover Date.     

Economically important seaweeds in Mar Piccolo,Taranto (southern Italy): a survey

A preliminary survey was carried out of the marine algae in the Mar Piccolo Basin, Taranto (southern Italy), in order to assess the degree of sewage pollution and to determine the presence of any economically important species that might be productively utilized. The following commercial species, belonging to a drift algal community, were found: Gracilaria bursapastoris, G. cf. verrucosa, Solieria sp. and S. filiformis. The species showed an aggregated distribution within the community and a clear cyclic annual pattern. Gracilaria bursa-pastoris exhibited the highest mean biomass values in May, whereas Solieria spp. were the most abundant in October. At the present time, only the harvesting of G. bursa-pastoris appears profitable. However, further detailed studies are required to more fully assess the standing crop of the Solieria spp. and G. cf. verrucosa. Considering the environmental situation in the basin, it might be more appropriate to cultivate, rather than harvest, these commercially important seaweeds. With the large number of sewage outlet plants available in the basin, the cultivation of seaweeds in a wastewater treatment-aquaculture system should be considered.