Identification and characterization of annexin gene family in rice

Plant annexins are Ca²⁺-dependent phospholipid-binding proteins and are encoded by multigene families. They are implicated in the regulation of plant development as well as protection from drought and other stresses. They are well characterized in Arabidopsis, however no such characterization of rice annexin gene family has been reported thus far. With the availability of the rice genome sequence information, we have identified ten members of the rice annexin gene family. At the protein level, they share 16–64% identity with predicted molecular masses ranging from 32 to 40 kDa. Phylogenetic analysis of rice annexins together with annexins from other monocots led to their classification into five different orthologous groups and share similar motif patterns in their protein sequences. Expression analysis by real-time RT-PCR revealed differential temporal and spatial regulation of these genes. The rice annexin genes are also found to be regulated in seedling stage by various abiotic stressors including salinity, drought, heat and cold. Additionally, in silico analysis of the putative upstream sequences was analyzed for the presence of stress-responsive cis-elements. These results provide a basis for further functional characterization of specific rice annexin genes at the tissue/developmental level and in response to abiotic stresses.     

Elemental metals as electron sources for biological methane formation from CO2

Several elemental metals were examined as potential electron donors for methanogenic bacteria, using both a single tube system where the metal was in direct contact with the cells, and a two-flask system, where metal and cells were not in direct contact, but had contact via the gas phase. With all organisms examined in the direct contact system, Fe^o, Al^o and Zn^o served as electron donors for methanogenesis; some organisms used Ni^o or Sn^o as low-level electron donors. Of the metals tested, methanogenesis from H₂+CO₂ was inhibited by direct contact with Zn^o or Cu^o, but not by Fe^o or Al^o. Ni^o and Co^o were inhibitory to some methanogens, with Ni^o being particularly inhibitory to the thermophilic strains tested. With all organisms examined in the two-flask system, Fe^o and Zn^o served as good electron sources for both methanogenesis and growth; Co^o generated a very low level of methane and Cu^o did not work at all. In either system V^o, Ti^o or Cd^o did not serve as electron donors. The results suggest that some elemental metals (notably Fe^o, Al^o and Zn^o) produce gaseous H₂ by cathodic depolarization which is then consumed by the methanogen, thus accelerating oxidation of the metal by its metabolic activity. All of these reactions are thermodynamically favorable; however, some other metals that are clearly favorable for such a reaction on thermodynamic grounds (Ti^o and V^o) are very stable and do not serve as electron donors.Preliminary results on this topic were presented at the Pan American Biodeterioration Society Meeting in Washington, D.C. July 28–31, 1988.     

PHOTOINHIBITION OF PHOTOSYNTHESIS IN ASTERIONELLA FORMOSA (BACILLARIOPHYCEAE)1, 2

A laboratory study was made of the inhibition of photosynthesis, as measured by the radiocarbon method, of Asterionella Formosa Hass. by light from tungsten halogen lamps of irradiances up to that of full sunlight. The observed inhibitions were of total fixation of carbon and were not due to greatly increased release of extracellular products of photosynthesis. Inhibition increased width irradiance and with time of exposure. It was greater at high temperature, at high oxygen concentrations and when the cells were nutrient deficient. Recovery from exposure to high irradiances took place both in the dark and at low irradiances. The inhibition, which is similar to that observed under natural conditions, has the characteristics of photooxidative damage to both photochemical and dark reaction mechanisms.     

The orchids of Timor: checklist and conservation status

A checklist of the Orchidaceae of Timor is presented, with emphasis on the eastern half of the island (East Timor), based on historical herbarium collections and recent botanical explorations. This list comprises 38 genera with 66 species, including 15 new genera and 32 new species records for this island. Moreover, four new species are described: Bulbophyllum sundaicum , Habenaria ankylocentron , Habenaria cauda‐porcelli , and Pterostylis timorensis . Of these, we consider the finding of a new species of Pterostylis to be especially noteworthy, because this species seems to be more closely related to certain Australian members of the genus than to the Malesian ones, suggesting earlier contacts of Timor with Australia. Four new synonyms are proposed: Calanthe veratrifolia var. timorensis J.J.Sm. (C. triplicata), Habenaria cornuta Span. (H. giriensis), H. grandis Benth. ex Ridl. (Peristylus goodyeroides), and H. mutica Span. (H. elongata). The best represented genus is Habenaria, with 13 species, followed by Dendrobium with four, and Bulbophyllum with three. Because of insufficient or sterile material, it was not possible to identify, or describe as new, 20 different taxa. The conservation status of the ten endemic species, plus six possible new undescribed species and two non‐endemic, but threatened, species, was assessed using the World Conservation Union (IUCN) criteria, and categories of threat were proposed. Seven endemic species are considered to be Critically Endangered and two Endangered. One of the nonendemic species is considered to be Critically Endangered, and the other Endangered. The survival of some of these species might be less insecure if an effective application of Regulation project N.2000/19 on protected areas (UNTAET/REG/2000/19) was implemented and maintained, because most of these species were collected in areas considered for protection under this Regulation. Further studies are required, however, in order to complete our knowledge of the diversity and population dynamics of this interesting part of Timor's biodiversity. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 157 , 197–215.     

Variation in fatty acid composition of <Emphasis Type="BoldItalic">Arthrospira</Emphasis> (Spirulina) strains

A study of the fatty acid composition was made for 35 Arthrospira strains, concentrating on the most abundant fatty acids, the two polyunsaturated C₁₈ acids, linoleic and γ-linolenic acid, and palmitic acid. When grown at 30 ^∘C and low irradiance (10 μmol photon m⁻² s⁻¹), these three acids together formed 88–92% of total fatty acids. There were considerable differences in the composition of the two polyunsaturated acids. Depending on the strain, linoleic acid formed 13.1–31.5% and γ-linolenic acid formed 12.9–29.4% total fatty acids. In contrast, the range for palmitic acid was narrow: 42.3–47.6% of total fatty acids. Repeat experiments on several strains under defined conditions led to closely similar results for any particular environment, suggesting that fatty acid composition can be used as an aid in differentiating between strains. Five additional strains, which had apparently originated from the same original stock cultures as 3 of the 35 in the main study, but from different culture collections, were also assayed. With four strains the results were similar, irrespective of culture source, but with one strain marked differences occurred, especially in the polyunsaturated C₁₈ fatty acid fraction. These differences were independent of the age of the culture. In addition, straight morphotypes derived during repeat subcultures of four strains; each showed a similar fatty acid composition to that of the helical morphotypes of the same strains. A decrease in temperature from 30 to 20 ^∘C, an increase in irradiance (at 30 ^∘C) from 10 to 70 μmol photon m⁻² s⁻¹ and transfer to dark heterotrophy all favoured an increase in polyunsaturated C₁₈ fatty acids. The highest γ-linolenic acid content of any conditions was found for three strains grown heterotrophically on glucose in the dark at 30 ^∘C. A comparative study of six strains of Spirulina confirmed a previous study showing the absence of γ-linolenic acid in all Spirulina strains, thus permitting the separation of these two genera.     

Species composition and phytoplankton biomass in a tropical African lake (Lake Awassa,Ethiopia)

The species composition and phytoplankton biomass of Lake Awassa, Ethiopia were studied from September 1985 to July 1986 in relation to some limnological features of the lake. During the study period, three phases of thermal stratification were recognized: a period of unstable stratification and near-complete mixing was followed by a stable stratification period and another period of complete mixing. Complete mixing was associated with cooling of air temperature with an influx of cool rain and high rainfall. The underwater light penetration showed a similar pattern over the whole period with the highest in the red, and the lowest in the blue spectral region. Euphotic depth varied between 1.6 and 3.0 meters with the highest measurements corresponding to the stable stratification period. PO₄-P concentrations ranged between 23 and 45 µg l^–1 and NO₃-N concentrations varied between 7 and 14 µg l^–1 during the study period. Both nutrients showed increasing values associated with mixing periods and/or the rainy season.A total of 100 phytoplankton species were identified with 48% of the taxa represented by green algae, 30% by blue-green algae, 11% by diatoms, and the rest by chrysophytes, dinoflagellates, cryptomonads and euglenoids. The dominant phytoplankton species were Lyngbya nyassae, Botryococcus braunii and Microcystis species. Seasonal biomass variation was pronounced in the first two species but not in Mycrocystis. Phytoplankton biomass increased following the mixing period in December, and thermal destratification during May to July which was also a period with high rainfall and relatively high nutrient concentration. While the seasonal variation of the total phytoplankton community in Lake Awassa was relatively low (coefficient of variation < 20%), it was higher in some of the individual component species.     

Occurrence of beta-glutamate, a novel osmolyte, in marine methanogenic bacteria

The unusual compound beta-aminoglutaric acid (beta-glutamate) has been identified by 13C nuclear magnetic resonance spectroscopy in soluble extracts of marine methanogenic bacteria. We examined several methanogen species representing nine genera and found that beta-glutamate occurred in methanococci and two methanogenium strains (Methanogenium cariaci JR1 and "Methanogenium anulus" AN9). The presence of this compound in the methanococci examined was further restricted to thermophilic members of the genus Methanococcus, including Methanococcus thermolithotrophicus strains, Methanococcus jannaschii, and "Methanococcus igneus." The two Methanogenium strains examined were mesophiles. Studies using Methanococcus thermolithotrophicus showed that levels of beta-glutamate in cells of that species were not affected by variation in growth temperature (40 to 65 degrees C), NH4+ (2 to 80 mM), Mg2+ (10 to 50 mM), or K+ (2 to 10 mM) in the medium. In contrast, soluble pools of beta-glutamate and L-alpha-glutamate (the other major free amino acid in all the methanococci) were proportional to NaCl levels in the growth medium. This dependence of beta-glutamate and L-alpha-glutamate concentrations on salt levels in the medium suggests that they function as osmolytes in these cells.     

Genetic prion disease: the EUROCJD experience

A total of 10–15% of human transmissible spongiform encephalopathies (TSEs) or prion diseases are characterised by disease-specific mutations in the prion protein gene (PRNP). We examined the phenotype, distribution, and frequency of genetic TSEs (gTSEs) in different countries/geographical regions. We collected standardised data on gTSEs between 1993 and 2002 in the framework of the EUROCJD collaborative surveillance project. Our results show that clinicopathological phenotypes include genetic Creutzfeldt–Jakob disease (gCJD), fatal familial insomnia (FFI), and Gerstmann–Sträussler–Scheinker disease (GSS). Genetic TSE patients with insert mutation in the PRNP represent a separate group. Point and insertional mutations in the PRNP gene varies significantly in frequency between countries. The commonest mutation is E200K. Absence of a positive family history is noted in a significant proportion of cases in all mutation types (12–88%). FFI and GSS patients develop disease earlier than gCJD. Base pair insertions associated with the Creutzfeldt–Jakob disease (CJD) phenotype, GSS, and FFI cases have a longer duration of illness compared to cases with point mutations and gCJD. Cerebrospinal fluid 14-3-3 immunoassay, EEG, and MRI brain scan are useful in the diagnosis of CJD with point mutations, but are less sensitive in the other forms. Given the low prevalence of family history, the term “gTSE” is preferable to “familial TSE”. Application of genetic screening in clinical practice has the advantage of early diagnosis and may lead to the identification of a risk of a TSE.Gábor G. Kovács and Maria Propolo Contributed equally