Rubisco Large Subunit Gene Research Articles

Physio-biochemical basis of iron-sulfide nanoparticle induced growth and seed yield enhancement in B. juncea

Metal nanoparticles have been reported to influence plant growth and productivity. However, the molecular mechanisms underlying the effects have not been completely understood yet. Current work describes the physio-biochemical basis of iron sulfide nanoparticle induced growth and yield enhancement in Brassica juncea. Iron sulfide nanoparticles (0, 2, 4, 6, 8 and 10 ppm) were used for foliar treatment of B. juncea at 30, 45 and 60 days after sowing, under field conditions. Foliar treatment of 4 ppm iron sulfide nanoparticle solution at 30 days after sowing brought maximal enhancement in agronomic attributes of the treated plants. Results of assays i.e. total chlorophyll, electrolyte leakage, Malondialdehyde (MDA), proline, H2O2 and antioxidant enzyme activities indicated the benign effect of iron sulfide nanoparticles on plants. Consequently, improved redox status of the treated plants, enabled them to assimilate higher photosynthate. The augmentation in growth and seed yield in iron sulfide nanoparticle treated plants was amply supported by activation of RUBISCO small subunit (rubisco S), RUBISCO large subunit (rubisco L), glutamine synthetase (gs) and glutamate synthase (gogat) genes. Thus, iron sulfide nanoparticle induced growth and yield enhancement is proposed to be mediated through activation of carbon and nitrogen assimilatory pathways at specific growth stage. The iron content in the leaves and root tissues of the treated plants was also significantly improved.

Systematic revision of the genus Reinboldiella (Ceramiaceae, Rhodophyta) from Taiwan based on comparative morphology and rbcL sequence analyses, including two new species of Reinboldiella

ABSTRACTThe genus Reinboldiella essentially consists of tiny, membranous blades, epiphytic on benthic red algae, with a wide distribution in the north-western Pacific Ocean (Taiwan, Korea and Japan). In this study, we re-examined the generitype R. schmitziana from Taiwan and neighbouring islands. Two new species of Reinboldiella, R. orientalis sp. nov. and R. taiwanensis sp. nov. are recognized from Taiwan based on comparative morphological studies and molecular analyses of RuBisCO large subunit (rbcL) gene sequences. Reinboldiella orientalis is characterized by its rosette-like appearance, with both erect and prostrate, membranous flat blades whereas R. taiwanensis is distinguishable by mainly consisting of erect, membranous blades with few, short prostrate blades in basal parts of the thalli. Thalli of R. schmitziana also have a rosette-like appearance, but their erect flat blades have cylindrical bases or stipes. The rbcL phylogenetic analyses also support the separation of R.‘schmitziana’ from Taiwan and R. schmitziana from Japan and Korea.

Revision of section Setacea of the genus Batrachospermum (Batrachospermales, Rhodophyta) with emphasis on specimens from Brazil

:This study evaluated the species level taxonomy and phylogenetic relationships among species of the section Setacea of the genus Batrachospermum. Molecular data (sequences of the plastid-encoded RuBisCO large subunit gene, rbcL; and the barcode region of the mitochondrial gene that encodes the cytochrome c oxidase subunit 1, cox1) were generated and morphological characters described for 15 populations from Brazil, Japan and Spain. The analyses of rbcL sequences revealed that section Setacea forms a well-supported clade, which was positioned close but clearly separated from some species of Batrachospermum usually called group ‘Australasica’. Three well-supported clades were formed within the section: Batrachospermum sp. from Brazil; Batrachospermum atrum from Australasia, Europe and Asia and Batrachospermum puiggarianum from South America. The analyses of cox1 sequences revealed two well-supported groups: a large group with the sequences of B. puiggarianum from Brazil and a small group with one sequence of B. atrum from Spain and two sequences of Batrachospermum sp. from Brazil. The interspecific variation among these three species was high (38–71 bp, 3.0–5.5% for rbcL; 37–51 bp, 5.6–7.5% for cox1); whereas, sequence divergences within these three clades were much lower (0–33 bp, 0–2.6% for rbcL; 0–15 bp, 0–2.3% for cox1). The section is raised to genus (Setacea), and three species were recognized, including two previously described species (Setacea atra and Setacea puiggariana) that can be separated by either molecular and morphological data. A third species could not be distinguished from S. atra by morphological evidence but is clearly distinct based on divergence levels of both molecular markers used in this study (5.6–6.2% for rbcL; 3.0–3.4% for cox1) and is proposed as a new species (Setacea atro-brasiliensis) with the known geographic distribution restricted to Brazil.

Rubisco catalytic properties of wild and domesticated relatives provide scope for improving wheat photosynthesis.

Rubisco is a major target for improving crop photosynthesis and yield, yet natural diversity in catalytic properties of this enzyme is poorly understood. Rubisco from 25 genotypes of the Triticeae tribe, including wild relatives of bread wheat (Triticum aestivum), were surveyed to identify superior enzymes for improving photosynthesis in this crop. In vitro Rubisco carboxylation velocity (V c), Michaelis-Menten constants for CO2 (K c) and O2 (K o) and specificity factor (S c/o) were measured at 25 and 35 °C. V c and K c correlated positively, while V c and S c/o were inversely related. Rubisco large subunit genes (rbcL) were sequenced, and predicted corresponding amino acid differences analysed in relation to the corresponding catalytic properties. The effect of replacing native wheat Rubisco with counterparts from closely related species was analysed by modelling the response of photosynthesis to varying CO2 concentrations. The model predicted that two Rubisco enzymes would increase photosynthetic performance at 25 °C while only one of these also increased photosynthesis at 35 °C. Thus, under otherwise identical conditions, catalytic variation in the Rubiscos analysed is predicted to improve photosynthetic rates at physiological CO2 concentrations. Naturally occurring Rubiscos with superior properties amongst the Triticeae tribe can be exploited to improve wheat photosynthesis and crop productivity.

Thorea indica sp. nov. (Thoreales, Rhodophyta) from Uttar Pradesh, India

Thorea indica sp. nov. is described from the Sai River, Uttar Pradesh, India (26°39′00.7″ N, 80°47′38.3″ E). Its classification is based on molecular sequences of the plastid-encoded RuBisCO large-subunit gene, rbcL and the barcode region of the mitochondrial encoded cytochrome c oxidase subunit 1, cox1, and morphological data. The sequence analyses confirm a new species of Thorea. The cox1 barcode sequence had 90.4-90.8% identity with Thorea sp. from Australia and Thorea hispida from Hawaii and China. Based on rbcL sequences the Indian specimen was positioned in a major clade with high support (>95 bootstrap and 0.95 posterior probability) containing two other species: T. okadae from Japan and T. hispida from the continental USA, Hawaii, the UK, and China. The divergences among these sequences were T. indica vs. T. okadae (2.8%) and T. indica vs. T. hispida (2.9-3.4%). The comparison of morphological characters of Thorea from India was not conclusive due to the inadequate descriptions in previous reports: most specimens reported as T. hispida fit within the circumscription of T. indica as described here. The previous report of T. siamensis from the Sai River is incorrect and the specimens fit within our description of T. indica. Thorea indica and T. okadae can be distinguished by minor morphometric characters and sexuality (dioecious vs. monoecious).

Bioregulators protected photosynthetic machinery by inducing expression of photorespiratory genes under water stress in chickpea

Globally, water deficit is one of the major constraints in chickpea (Cicer arietinum L.) production due to substantial reduction in photosynthesis. Photorespiration often enhances under stress thereby protecting the photosynthetic apparatus from photoinhibition. Application of bioregulators is an alternative to counter adverse effects of water stress. Thus, in order to analyze the role of bioregulators in protecting the photosynthetic machinery under water stress, we performed an experiment with two contrasting chickpea varieties, i.e., Pusa 362 (Desi type) and Pusa 1108 (Kabuli type). Water deficit stress was imposed at the vegetative stage by withholding water. Just prior to exposure to water stress, plants were pretreated with thiourea (1,000 mg L−1), benzyladenine (40 mg L−1), and thidiazuron (10 mg L−1). Imposed water deficit decreased relative water content (RWC), photosynthetic rate (PN), quantum efficiency of PSII (Fv/Fm), and enhanced lipid peroxidation (LPO). However, bioregulator application maintained higher RWC, PN, Fv/Fm, and lowered LPO under water stress. Expression of Rubisco large subunit gene (RbcL) was low under water stress both in the Kabuli and Desi type. However, bioregulators strongly induced its expression. Although poor expression of two important photorespiratory genes, i.e., glycolate oxidase and glycine decarboxylase H subunit, was observed in Desi chickpea under imposed stress, bioregulators in general and cytokinins in particular strongly induced their expression. This depicts that the application of bioregulators protected the photosynthetic machinery by inducing the expression of RbcL and photorespiratory genes during water deficit stress.

Deep genetic divergence between austral populations of the red alga Gigartina skottsbergii reveals a cryptic species endemic to the Antarctic continent

The almost complete isolation of Antarctica after the intensification the Antarctic circumpolar current (ACC) during the middle-Miocene has been challenged by recent molecular data showing the existence of allelic exchange across the ACC. For organisms present on both sides of the ACC, two hypotheses have then been discussed to explain the origin of the Antarctic populations: (1) They correspond to recent immigrants from adjacent continents, or (2) they have evolved in situ and have survived the dramatic effects of the last Quaternary glaciations in this region. The red algae Gigartina skottsbergii presents a disjoint distribution and is reported in both Antarctica and southern South America, a distribution pattern that largely exceeds its dispersal capacity. Mitochondrial sequences of the intergenic region Cox2-3 (n = 233) and partial chloroplastic RuBisCo large subunit gene (n = 26) sequences were obtained for individuals from the Chilean sub-Antarctic ecoregion and Antarctic Peninsula localities. The results strongly support the persistence of populations on each side of the Drake Passage during glacial periods and the existence of dispersal barrier due to the ACC. On both sides of the ACC, the last Quaternary glaciations have induced strong bottlenecks that were followed by rapid colonization events.

Paralia (Bacillariophyta) stowaways in ship ballast: implications for biogeography and diversity of the genus.

BackgroundThe genus Paralia Heiberg is one of the most recognizable, widely distributed and commonly reported diatoms from contemporary coastal marine environments and ship ballast. Species discovery has historically been made in diatoms through the recognition of morphological discontinuities between specimens, first using light and later electron microscopy. However, recently, morphologically semi-cryptic species of Paralia were delineated using genetic analyses, among mostly tropical and subtropical sites.ResultsTen morphological characters of the frustules and sequence fragments from the nuclear genome (conserved 18S regions of ribosomal RNA and the variable internal transcribed spacer [ITS]), and from the RuBisCo large subunit (rbcL) gene of the chloroplast genome were examined. Frustule morphology did not segregate species, however, comparisons of sequence fragments and ITS2 secondary structures yielded a new species from North American waters, P. guyana (with four genodemes), and another widely-distributed species, P. marina. The latter was lecto- and epitypified here because it is most similar to specimens in the type preparation BM1021 representing Smith’s concept of the species. Paralia marina and certain genodemes of P. guyana were morphologically cryptic. Only those genodemes of P. guyana that possess prickly separation valves could be morphologically distinguished from P. marina with relative confidence in SEM preparations. All clones established from chains isolated from the ballast sediment of the ships sailing along the Atlantic coast of North America belonged to P. guyana. All DNA sequences of preserved Paralia chains recovered from the three trans-Atlantic voyages (TAVs) samples arriving to eastern Canada from Europe shared 100% identity with P. marina.ConclusionFirst, if the overline{x} = 130592 P. marina cells per ballast tank at the end of the TAVs represents their abundance in ballast tanks of similar crossings and following mid-ocean ballast water exchange, then this diatom, if de-ballasted, exerts a strong and continued propagule pressure on Eastern Canadian coasts. Despite this, as of 2009, P. marina was found only in Cheticamp, Nova Scotia, Canada. Second, genetic analysis readily segregated cryptic and semi-cryptic taxa of Paralia, highlighting the usefulness of the molecular approach to species recognition, e.g., in programs monitoring alien introductions.Electronic supplementary materialThe online version of this article (doi:10.1186/s40709-015-0024-5) contains supplementary material, which is available to authorized users.

Systematics of the section Virescentia of the genus Batrachospermum (Batrachospermales, Rhodophyta) in Brazil

:This study evaluated the species level taxonomy and phylogenetic relationships among species of the section Virescentia of the genus Batrachospermum focusing on specimens from Brazil and other regions of the world. Molecular data (sequences of the plastid-encoded RuBisCO large-subunit gene, rbcL; and the barcode region of the mitochondrial encoded cytochrome c oxidase subunit 1, cox1) were generated, and morphological characters described for 13 populations. Molecular analyses of rbcL sequences revealed the existence of three well-supported clades with evident biogeographic trends, containing sequences of specimens of either North America (USA), Asia (Japan) or Brazil. Similarly, analysis of cox1 sequences (slightly different taxon sampling) also revealed three clades, containing specimens of either North America (USA), Europe (Norway) or Brazil. The three species recognized from Brazil in a previous study based on morphological data (Batrachospermum helminthosum, B. sirodotii and B. vogesiacum) could not be distinguished by molecular or morphological data. A new species was proposed for Brazilian specimens based on molecular and morphological evidence. Batrachospermum viride-brasiliense differed from the European species of the section Virescentia (B. bruziense, B. coerulescens, B. elegans, B. sirodotii and B. vogesiacum) by the longer carpogonia (≥ 40 μm) and larger carposporophytes (≥ 200 μm in diameter and ≥ 100 μm high) and carposporangia (≥ 19 μm long and ≥ 10 μm in diameter).

Photosynthesis and growth in diverse willow genotypes

AbstractDuring a study of the contribution of photosynthetic traits to biomass yield among 11 diverse species of willow, the light and CO2 dependence of photosynthesis were found to differ, with absolute rates at ambient and saturating CO2, together with maximum rates of Rubsico‐limited and electron‐transport‐limited photosynthesis (Vcmax and J, respectively) varying by factors in excess of 2 between the extremes of performance. In spite of this, the ratio, J/Vcmax – indicative of the relative investment of resource into RuBP regeneration and RuBP carboxylation – was found to fall within a narrow range (1.9–2.5) for all genotypes over two successive years. Photosynthetic rate (μmol CO2 fixed m−2 sec−1) showed a strong, inverse correlation with total leaf area per plant. Photosynthetic capacity, expressed on a leaf area basis, showed a strong, positive correlation with yield among some of the species, but when expressed on a whole plant basis all species indicated a positive correlation with yield. Thus, both leaf area per plant and photosynthetic rate per unit leaf area contribute to this relationship. The abundance and kinetic characteristics of Rubisco play a pivotal role in determining photosynthetic rate per unit leaf area and so were determined for the chosen willow species, in parallel with Rubisco large subunit (LSU) gene sequencing. Significant differences in the rate constants for carboxylation and oxygenation as well as the affinity for CO2 were identified, and rationalized in terms of LSU sequence polymorphism. Those LSU sequences with isoleucine instead of methionine at residue 309 had up to 29% higher carboxylase rate constants. Furthermore, the A/Ci curves predicted from each distinct set of Rubisco kinetic parameters under otherwise identical conditions indicated substantial differences in photosynthetic performance. Thus, genetic traits relating specifically to Rubisco and by implication to photosynthetic performance were also identified.

DNA barcoding assessment of green macroalgae in coastal zone around Qingdao, China

An assessment with assistance of DNA barcoding was conducted on green macroalgae in coastal zone around Qingdao, China, during the period of April–December, 2011. Three markers were applied in molecular discrimination, including the plastid elongation factor tufA gene, the internal transcribed spacer (ITS) region of the ribosomal cistron and rubisco large subunit gene 3′ regions (rbcL-3P). DNA barcoding discriminated 8 species, excluding species of genus Cladophora and Bryopsis due to failures in amplification. We ascertained and corrected 4 species identified by morphological methods for effectively assisting the classification. The gene tufA presented more advantages as an appropriate DNA marker with the strongest amplification success rate and species discrimination power than the other two genes. The poorest sequencing success largely handicapped the application of ITS. Samples identified by tufA and rbcL as Ulva flexuosa were clustered into the clade of U. prolifera by ITS in the neighbor-joining tree. Confusion with discrimination of the complex of U. linza, U. procera and U. prolifera (as the LPP complex) still existed for the three DNA markers. Based on our results, rbcL is recommended as a preferred marker for assisting tufA to discriminate green macroalgae. In distinguishing green-tide-forming Ulva species, the free-floating sample collected from the green tide in 2011 was proved to be identical with U. prolifera in Yellow Sea for ITS and rbcL genes. This study presents a preliminary survey of green macroalgae distributed in the coastal area around Qingdao, and proves that DNA barcoding is a powerful tool for taxonomy of green macroalgae.

Resolving phenotypic plasticity and species designation in the morphologically challenging Caulerpa racemosa-peltata complex (Chlorophyta, Caulerpaceae).

Although recent molecular studies have indicated the presence of a number of distinct species within the Caulerpa racemosa-peltata complex, due to the difficulties presented by high levels of phenotypic plasticity and the large number of synonyms, infra-specific taxa, and names of uncertain affinity, taxonomic proposals are yet to be made. In this study, we aimed to resolve the taxonomy of the complex and provide an example of how historical nomenclature can best be integrated into molecular based taxonomies. We accomplished this by first determining the number of genetic species within our globally sampled data set through a combination of phylogenetic and species-delimitation approaches of partial elongation factor TU and RUBISCO large subunit gene sequences. Guided by these results, comparative morphological examinations were then undertaken to gauge the extent of phenotypic plasticity within each species, as well as any morphological overlap between them. Our results revealed the presence of 11 distinct species within the complex, five of which showed high levels of phenotypic plasticity and partial overlap with other species. On the basis of observations of a large number of specimens, including type specimens/descriptions, and geographic inferences, we were able to confidently designate names for the lineages. Caulerpapeltata, C.imbricata and C.racemosa vars. laetevirens, occidentalis and turbinata were found to represent environmentally induced forms of a single species, for which the earlier-described C.chemnitzia, previously regarded as a synonym of C.racemosa var. turbinata, is reinstated. C.cylindracea, C.lamourouxii, C.macrodisca, C.nummularia and C.oligophylla are also reinstated and two new species, C.macra stat. nov. and C.megadisca sp. nov., are proposed.

Diversity of Endosymbiotic Nostoc in Gunnera magellanica (L) from Tierra del Fuego, Chile

Global warming is causing ice retreat in glaciers worldwide, most visibly over the last few decades in some areas of the planet. One of the most affected areas is the region of Tierra del Fuego (southern South America). Vascular plant recolonisation of recently deglaciated areas in this region is initiated by Gunnera magellanica, which forms symbiotic associations with the cyanobacterial genus Nostoc, a trait that likely confers advantages in this colonisation process. This symbiotic association in the genus Gunnera is notable as it represents the only known symbiotic relationship between angiosperms and cyanobacteria. The aim of this work was to study the genetic diversity of the Nostoc symbionts in Gunnera at three different, nested scale levels: specimen, population and region. Three different genomic regions were examined in the study: a fragment of the small subunit ribosomal RNA gene (16S), the RuBisCO large subunit gene coupled with its promoter sequence and a chaperon-like protein (rbcLX) and the ribosomal internal transcribed spacer (ITS) region. The identity of Nostoc as the symbiont was confirmed in all the infected rhizome tissue analysed. Strains isolated in the present study were closely related to strains known to form symbioses with other organisms, such as lichen-forming fungi or bryophytes. We found 12 unique haplotypes in the 16S rRNA (small subunit) region analysis, 19 unique haplotypes in the ITS region analysis and 57 in the RuBisCO proteins region (rbcLX). No genetic variability was found among Nostoc symbionts within a single host plant while Nostoc populations among different host plants within a given sampling site revealed major differences. Noteworthy, interpopulation variation was also shown between recently deglaciated soils and more ancient ones, between eastern and western sites and between northern and southern slopes of Cordillera Darwin. The cell structure of the symbiotic relationship was observed with low-temperature scanning electron microscopy, showing changes in morphology of both cyanobiont cells (differentiate more heterocysts) and plant cells (increased size). Developmental stages of the symbiosis, including cell walls and membranes and EPS matrix states, were also observed.

Effect of land use on the abundance and diversity of autotrophic bacteria as measured by ribulose-1,5-biphosphate carboxylase/oxygenase (RubisCO) large subunit gene abundance in soils

Elucidating the biodiversity of CO2-assimilating bacterial communities under different land uses is critical for establishing an integrated view of the carbon sequestration in agricultural systems. We therefore determined the abundance and diversity of CO2 assimilating bacteria using terminal restriction fragment length polymorphism and quantitative PCR of the cbbL gene (which encodes ribulose-1,5-biphosphate carboxylase/oxygenase). These analyses used agricultural soils collected from a long-term experiment (Pantang Agroecosystem) in subtropical China. Soils under three typical land uses, i.e., rice–rice (RR), upland crop (UC), and paddy rice–upland crop rotation (PU), were selected. The abundance of bacterial cbbL (0.04 to 1.25 × 108 copies g−1 soil) and 16S rDNA genes (0.05–3.00 × 1010 copies g−1 soil) were determined in these soils. They generally followed the trend RR > PU > UC. The cbbL-containing bacterial communities were dominated by facultative autotrophic bacteria such as Mycobacterium sp., Rhodopseudomonas palustris, Bradyrhizobium japonicum, Ralstonia eutropha, and Alcaligenes eutrophus. Additionally, the cbbL-containing bacterial community composition in RR soil differed from that in upland crop and paddy rice–upland crop rotations soils. Soil organic matter was the most highly statistically significant factor which positively influenced the size of the cbbL-containing population. The RR management produced the greatest abundance and diversity of cbbL-containing bacteria. These results offer new insights into the importance of microbial autotrophic CO2 fixation in soil C cycling.

Molecular phylogeny and developmental studies of Apoglossum and Paraglossum (Delesseriaceae, Rhodophyta) with a description of Apoglosseae trib. nov.

Our morphological and molecular studies indicate that species from the southern hemisphere previously placed in Delesseria belong in Paraglossum and that Paraglossum and Apoglossum comprise a separate tribe, the Apoglosseae, S.-W. Lin, Fredericq & Hommersand, trib. nov., within the family Delesseriaceae. From a vegetative perspective the Apoglosseae is readily recognized because some or all fourth-order cell rows are formed on the inner sides of third-order cell rows. All fourth-order cell rows grow adaxially in Apoglossum, whereas both adaxial and abaxial cell rows are present in Paraglossum. Periaxial cells do not divide in Apoglossum, whereas they divide transversely in Paraglossum in the same way as in Delesseria. Major branches are formed mainly from the margins of midribs in the Apoglosseae. The procarp consists of a straight carpogonial branch and two sterile cells, with the second formed on the same side as the first. The carpogonium cuts off two connecting cells in tandem from its apical end, the terminal cell being nonfunctional and the subterminal cell typically fusing with the auxiliary cell. Gonimoblast filaments radiate in all directions from the gonimoblast initials and produce carposporangia terminally in branched chains, with pit connections between the inner gonimoblast cells broadening and enlarging. The auxiliary cell, supporting cell, and sterile cells unite into a fusion cell, which remains small in Apoglossum but incorporates the branched inner gonimoblast filaments and cells in the floor of the cystocarp in Paraglossum. Elongated inner cortical cells seen in mature cystocarps in the Delesserieae are absent in the Apoglosseae. Phylogenetic studies based on rbcL (RuBisCO large subunit gene) sequence analyses strongly support the recognition of the Apoglosseae within the subfamily Delesserioideae of the Delesseriaceae, in agreement with our previous observations based primarily on analyses of large subunit ribosomal DNA (LSU).

Algal Biogeography: Metagenomics Shows Distribution of a Picoplanktonic Pelagophyte

How can we determine the distribution of uncultured marine microorganisms? Targeted metagenomics has provided the complete chloroplast genome sequence, and the distribution, for a picoplanktonic pelagophyte alga.

Microbial CO2 fixation potential in a tar-oil-contaminated porous aquifer

CO(2) fixation is one of the most important processes on the Earth's surface, but our current understanding of the occurrence and importance of chemolithoautotrophy in the terrestrial subsurface is poor. Groundwater ecosystems, especially at organically polluted sites, have all the requirements for autotrophic growth processes, and CO(2) fixation is thus suggested to contribute significantly to carbon flux in these environments. We explored the potential for autotrophic CO(2) fixation in microbial communities of a petroleum hydrocarbon-contaminated aquifer by detection of functional marker genes (cbbL, cbbM), encoding different forms of the key enzyme RubisCO of the Calvin-Benson-Bassham cycle. Quantification of (red-like) cbbL genes revealed highest numbers at the upper fringe of the contaminant plume and the capillary fringe where reduced sulphur and iron species are regularly oxidized in the course of groundwater table changes. Functional gene sequences retrieved from this area were most closely related to sequences of different thiobacilli. Moreover, several cultures could be enriched from fresh aquifer material, all of which are able to grow under chemolithoautotrophic conditions. A novel, nitrate-reducing, thiosulfate-oxidizing bacterial strain, recently described as Thiobacillus thiophilus D24TN(T) sp. nov., was shown to carry and transcribe RubisCO large-subunit genes of form I and II. Enzyme tests proved the actual activity of RubisCO in this strain.

Diversity and expression of different forms of RubisCO genes in polluted groundwater under different redox conditions

Groundwater polluted with methyl-tert-butyl ether (MTBE) and ammonium was investigated for chemolithoautotrophic CO(2) fixation capabilities based on detailed analyses of ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) large subunit genes. Samples retrieved from a groundwater conditioning unit, characterized by different redox conditions, were examined for the presence of form IA, form IC (cbbL) and form II (cbbM) RubisCO genes and transcripts obtained from DNA- and RNA-extracts. Form IA RubisCO sequences, which revealed a complex and distinct variety in different sampling stations, were expressed in the original groundwater and in samples amended with oxygen, but not in the aquifer groundwater enriched with nitrate. Form IC RubisCO genes were exclusively detected in groundwater supplied with oxygen and sequences were affiliated with cbbL genes in nitrifying bacteria. cbbM genes were not expressed in the oxygen-amended groundwater, probably due to the low CO(2) /O(2) substrate specificity of this enzyme. Most form II RubisCO transcripts were affiliated with RubisCO genes of denitrifiers, which are important residents in the groundwater supplied with nitrate. The distinct distribution pattern and diversity of RubisCO genes and transcripts obtained in this study suggest that the induction of different RubisCO enzymes is highly regulated and closely linked to the actual environmental conditions.

Toxicity and genetic diversity of Cylindrospermopsis raciborskii in Florida, USA

Cylindrospermopsis raciborskii is a potentially toxic cyanobacterium which has become increasingly prominent in algal blooms throughout the USA. Twenty strains of C. raciborskii isolated from Florida, and one strain from Indiana (USA), were tested for the ability to produce three toxins, cylindrospermopsin, microcystin and saxitoxin using newly developed Polymerase Chain Reaction (PCR) primers and Enzyme Linked Immunosorbent Assays (ELISA). None of these strains demonstrated the ability to produce any of the three toxins. Phylogenetic analyses of 16S rRNA gene sequences, a common genetic marker used in taxonomic differentiation, did not delineate these isolates from other C. raciborskii strains. However, Rubisco Large Subunit gene sequences, a less commonly used but useful genetic marker, provided better resolution of differences between Florida strains of C. raciborskii and those from Australia, which are known to be toxic. There may be toxic strains of C. raciborskii in the USA, but none were found among the Florida and Indiana strains examined, suggesting that strains of C. raciborskii in Florida lakes, and perhaps other regions of North America, may not be toxic. The potential management implications of this observation warrant further exploration of the toxicity of this species in the Americas.

Uniparental Inheritance of Chloroplast DNA Is Strict in the Isogamous Volvocalean Gonium

BackgroundA problem has remained unresolved regarding the exceptions to the unilateral inheritance of chloroplast DNA (cpDNA) from MT+/female in Chlamydomonas and other volvocaleans demonstrated by the previous genetic analyses. For identification of the parental types of cpDNA, these studies used parents that have differences in restriction fragment length polymorphisms and exhibit partial sexual incompatibility.Methodology/Principal FindingsIn the present study, we used sexually compatible parents of the isogamous colonial volvocalean Gonium maiaprilis that seemed an ideal species to identify the pattern of cpDNA inheritance based on the length difference in the putative group I intron interrupted in the Rubisco large subunit gene and objective identification of mating types by the presence or absence of the minus-dominance (MID) gene. We examined patterns of inheritance of cpDNA and presence/absence of a MID ortholog (GmMID) in 107 F1 progeny of G. maiaprilis that were obtained by inducing germination of separated single zygotes. The results demonstrated no exception of the uniparental inheritance of cpDNA from the MT+ parent (lacking GmMID) in sexually compatible or genetically less divergent strains of G. maiaprilis.Conclusions/SignificanceThe present data suggest that the uniparental inheritance of cpDNA is likely more strict in crossings of less diverged strains or sexually compatible parental volvocaleans, and some genetic inconsistency between the parents may cause exceptional uniparental inheritance of cpDNA.