The salt relations of Dunaliella

Dunaliella tertiolecta (marine) and D. viridis (halophilic) were each trained by serial transfer to growth at salt concentrations previously regarded as the other's domain. D. viridis then had a salt optimum at 1.0–1.5 M sodium chloride whereas that for D. tertiolecta was less than 0–2 M. Nevertheless D. tertiolecta grew faster than the halophil at all salt concentrations up to 3.5 M, the highest at which they were compared.Both species accumulate glycerol, which is necessary for growth at elevated salinities and which responds in its content to water activity (a _w ) rather than specifically to salt concentration. Variation in glycerol content is a metabolic process which occurs in the dark from accumulated starch as well as photosynthetically. Regulation of glycerol content by a _w does not require protein synthesis. The NADP-specific glycerol dehydrogenase of each of the algae is likely to be directly involved in the regulation of glycerol content. Kinetic studies, together with those described in an earlier publication, show that the enzyme has regulatory properties, and that both glycerol and dihydroxyacetone act as effectors as well as reactants. A mechanism of the reaction is tentatively proposed.     

Transient reduction in secreted 32 kD chitinase prevents somatic embryogenesis in the carrot (Daucus carota L.) variant ts11

At the nonpermissive temperature, somatic embryos of the temperature-sensitive (ts) carrot (Daucus carota L.) cell variant ts11 only proceed beyond the globular embryo stage in the presence of medium conditioned by wild-type cells. The causative component in the conditioned medium has been identified as an acidic 32 kD endochitinase. An antiserum raised against the 32 kD chitinase detected this protein in culture medium from ts11 embryo cultures grown at the permissive temperature as well as at the nonpermissive temperature. No difference in biochemical characteristics or in effect on ts11 embryo development could be detected between the 32 kD chitinase purified from wild-type cultures and the chitinase from ts11 cultures grown at the permissive or at the nonpermissive temperature. Compared to the amount present in a ts11 embryo culture at the permissive temperature, a reduction in the amount of 32 kD chitinase was observed during the temperature-sensitive period at the nonpermissive temperature. These results imply that the arrested embryo phenotype of ts11 is not the result of a structural difference in its 32 kD chitinase, but is the result of a transient decrease in the amount of 32 kD chitinase present. Morphological observations indicate that the ts11 phenotype is pleiotropic and also affects the cell wall of nonembryogenic cells. © 1995 Wiley-Liss, Inc.     

A two-element Enhancer-Inhibitor transposon system in Arabidopsis thaliana

The Enhancer-Inhibitor (En-I), also known as Suppressor-mutator (Spm-dSpm), transposable element system of maize was modified and introduced into Arabidopsis by Agrobacterium tumefaciens transformation. A stable En/Spm transposase source under control of the CaMV 35S promoter mediated frequent transposition of I/dSpm elements. Transposition occurred continuously throughout plant development over at least seven consecutive plant generations after transformation. New insertions were found at both linked and unlinked positions relative to a transposon donor site. The independent transposition frequency was defined as a transposition parameter, which quantified the rate of unique insertion events and ranged from 7.8% to 29.2% in different populations. An increase as well as a decrease in I/dSpm element copy number was seen at the individual plant level, but not at the population level after several plant generations. The continuous, frequent transposition observed for this transposon system makes it an attractive tool for use in gene tagging in Arabidopsis.     

Two new parrot species (Psittaciformes) from the early Pliocene of Langebaanweg,South Africa,and their palaeoecological implications

Two new parrot species (Psittaciformes) are described from the early Pliocene Varswater Formation at Langebaanweg, South Africa, an area where no parrots currently are found. A coracoid, humeri, ulnae, carpometacarpi, tibiotarsi and tarsometatarsi of at least four individuals are assigned to a new species of lovebird Agapornis. Additional tarsometatarsi of at least five individuals including a nestling are referred to a new genus and species of Psittacinae, a taxon endemic to Africa comprising the extant genera Poicephalus and Psittacus. Both species form the as yet earliest geological record of parrots in Africa and document the early diversification of the taxa Agapornis and Psittacinae. Evidence for parrots in general, and a putative graminivorous species of lovebird in particular, indicates that woodlands as well as grasslands were present at Langebaanweg during the early Pliocene, which is consistent with current hypotheses on the palaeoenvironment at and around this site.     

Composition and Distribution of Recent Marine Ostracod Assemblages in the Bottom Sediments of Central Aegean Sea (SE Andros Island,Greece)

The present study provides a thorough analysis of the composition of recent marine ostracod populations from the bottom sediments of the central Aegean Sea, as well as their distribution patterns. In particular, a detailed qualitative and quantitative study of living ostracod assemblages was carried out in the marine environments of SE Andros Island. Sampling took place at Kastro and Korthi Gulf, both located at the southeastern coast of the Andros Island and from depth of 1.5 to 18 m, while additional samples were collected outside the gulfs at a depth of 120–180 m. Only ostracods considered to have been living at the time of collection were picked from the samples. A total of 51 species belonging to 34 genera were identified and four main ostracod assemblages, representing different biotopes, were distinguished. The results produced from the application of Q‐mode cluster analysis in the data set, the calculated assemblage structure indices for each sample, as well as the bathymetric and granulometric data are as follows: Hiltermannicythere rubra assemblage (occurs in substrates of sandy mud and at a water depth ranging from 40–60 m to the depth of 100 m or even more), Loxoconcha affinis, Xestoleberis sexmaculata assemblage (occurs in substrates of muddy very fine to fine sands and shallower environments), Semicytherura incogruens assemblage (occurs in very fine sands at a water depth from 10 to 28 m), Loculicytheretta pavonia and Neocytherideis fasciata, Pontocythere turbita assemblages (occurs mainly in fine sands and at a water depth between 3.5 and 15 m) and Urocythereis neapolitana assemblage (occurs in substrates of medium to coarse sand and at a water depth of less than 20 m). (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Urethane and N-nitrosodiethylamine are mutagenic for the Syrian hamster fetus

Urethane and N-nitrosodiethylamine are soluble environmental carcinogens that initiate tumors transplacentally, but have a mixed history of effectiveness in mutagenesis assays in vitro or in vivo with adult rodents. To test for their transplacental mutagenicity, Syrian hamster fetuses at 12 days in gestation were exposed transplacentally to urethane or N-nitrosodiethylamine at 0.5 or 1.0 mM/kg. The fetal cells were isolated on day 13 of gestation and tested for diphtheria toxin resistance as a mutation marker. Both compounds were significantly mutagenic, at both doses, causing 6- to 20-fold increases in mutations compared with controls. Compared with N-nitrosodiethylamine, urethane was somewhat more effective as a mutagen with a more marked dose–response. These results are consistent with mutagenesis as part of the mechanism of transplacental carcinogenicity of urethane and N-nitrosodiethylamine.     

Exotic fish species in a global biodiversity hotspot: observations from River Chalakudy,part of Western Ghats,Kerala, India

We record here the occurrence of five exotic fish species viz Oreochromis mossambicus, Gambusia affinis, Osphronemus goramy, Xiphophorus maculatus and Poecilia reticulata in the Chalakudy River, part of the Western Ghats, a global biodiversity hotspot in Kerala, India. O. mossambicus was ubiquitous in occurrence with large shoals being encountered at all sampling sites spread along the downstream-upstream gradient of the river, including at an altitude of 1050 m ASL. Osphronemus goramy was recorded from the downstream region of the river while Gambusia affinis was recorded from three sampling sites located downstream as well as midstream. Xiphophorus maculatus was collected from a second order stream flowing through a tea plantation at an altitude of 1050 m ASL. Samples of brooders and early fry of Poecilia reticulata indicate that the fish has already established a breeding population in the river. Possible threats to the indigenous fish fauna of the Chalakudy River as a result of the invasion and proliferation of these exotics is discussed.     

Multi‐scale habitat selection of Mus minutoides in the Lowveld of Swaziland

We investigated habitat selection of Mus minutoides in northeastern Swaziland. We used powder tracking to determine how M. minutoides selected habitat at a fine scale and a broader path scale. At the fine scale, we measured per cent cover of grass and shrubs, the number of forbs and visual obstruction (VO) at five evenly spaced points along a mouse's pathway and at a paired random location. At the path scale, we calculated the relative displacement (RD) of each path as the ratio of the distance from the start to the end point of the path to the total length of the path (values near one indicate less preference). We found that M. minutoides were positively associated with increases in visual obstruction, grass cover, and shrub cover at the fine scale, but not at the path scale. Our results indicate that M. minutoides selection of vegetative features at the path scale is not as important as their fine‐scale selection of vegetative structure. In addition, the shrub encroachment on our study site may be directly beneficial to M. minutoides at the fine scale. Our results provide us with an increased understanding of the basic ecology of M. minutoides and information on their response to a changing landscape.     

Some factors affecting size distribution and density of grass shrimp (Palaemonetes pugio) populations in two New Jersey estuaries

Mature Palaemonetes pugio, from a polluted estuary, Piles Creek (PC) are larger than those in a more pristine estuary in Tuckerton (TK). Possible causes for the differences in size-structure could be differences in environmental factors at the two creeks, differential competition at the two sites, inherent factors causing a greater growth rate in the PC population, differences in reproductive timing, or differential predation at the two sites. Lab microcosm studies were used to examine the possibility of inherent population differences or environmental conditions (including differences in salinity) causing faster growth in PC. There was no evidence that PC shrimp grew faster than TK shrimp, nor that PC conditions fostered greater growth compared to TK. Salinity adjustments in PC and TK tanks also had no effect on growth. Therefore, it appears that genetic and environmental factors did not play a significant role in greater shrimp growth in PC. In the field, data on relative abundances of Fundulus heteroclitus and P. pugio, and size-frequency distributions of P. pugio were collected from the two estuaries. Gravid females and recruits of young shrimp physically appeared at approximately the same time within both systems, eliminating earlier reproduction as a cause of the size discrepancy. There were three times as many shrimp in PC than in TK (eliminating the possibility of increased population density and competition at TK as a cause) and three times as many F. heteroclitus present in TK than in PC. Since it has already been established that the Fundulus at PC are smaller than at TK and that they are poor predators, differences in Fundulus predation would appear to be an important factor in determining the number and size-frequency of the grass shrimp.     

Suggestive evidence of association of C-159T functional polymorphism of the <Emphasis Type="Italic">CD14</Emphasis> gene with atopic asthma in northern and northwestern Indian populations

CD14 is a lipopolysaccharide receptor known to be an important modulator of Th1–Th2 response during early childhood. Genetic association studies of the CD14 gene with asthma and atopic disorders have shown positive as well as negative results in different ethnic populations. The aim of this study was to test for association of C-159T functional promoter polymorphism with atopic asthma and serum IgE levels in northern and northwestern Indian populations. DNA was assayed for the CD14 C-159T polymorphism in a case-control study involving atopic asthmatics (n=187) and healthy normal controls (n=227), and in a family-based association study of 106 trios. The case-control study showed an association at the genotypic (P=0.0146) as well as the allelic level (P=0.0048). Moreover, we observed a deviation of allelic transmission from random proportions (P=0.024) in the transmission disequilibrium test analysis. When we analyzed our results for serum total IgE levels, against this polymorphism, we observed a difference at the genotypic (P=0.0026) as well as at the allelic level (P=0.0016) in a case-control study, whereas no association in the quantitative transmission disequilibrium test analysis was obtained. These findings provide suggestive evidence of association of the CD14 gene locus with atopic asthma in northern and northwestern Indian populations.     

Variations in the cultural characteristics of Rhizoctonia solani,and its antagonists: Aspergillus terreus and Aspergillus flavus occurring in the rhizosphere of cotton

Summary Cultural studies onRhizoctonia solani, the causal agent of damping-off of cotton, as well as on two fungi of its antagonistic rhizospheric microflora, namelyAspergillus terreus andAspergillus flavus have shown coincidence of some of their cultural characteristics. However,R. solani produced mycelial growth far ahead both antagonists except at 37° C and at pH 4, at its optimum temperature. It is expected that for a successful biological control ofR. solani in the soil,A. terreus is applied at a soil-temperatured above 35° C in an acid medium.     

Effects of micro-environmental factors on photosynthetic CO2 uptake and carbon fixation metabolism in a spring ephemeral, Erythronium japonicum, growing in native and open habitats

Microenvironmental factors and physiological parameters (such as water potential, activity of ribulose 1,5-bisphosphate carboxylase (RuBPcase), levels of ribulose 1,5-bisphosphate (RuBP), 3-phosphoglyceric acid (PGA) and sucrose in leaves) affecting photosynthetic processes of the typical vernal species Erythronium japonicum Decne. were examined on the floor of a deciduous broad-leaved Quercus mongolica forest (Q.m. stand) and on bare land left undisturbed for 7 years after forest clearing (bare stand). Daytime solar radiation and the air and leaf temperatures at the bare stand were significantly higher than those at the Q.m. stand. The relative air humidity was very low and did not differ much between the stands, whereas the leaf–air vapor pressure difference (VPD) at the bare stand was twice as high as that at the Q.m. stand. The water potential in leaves at the bare stand was lower than two times that at the Q.m. stand. Therefore, the aboveground parts of the plants at the bare stand were subjected to much more severe heat stress than those at the Q.m. stand. When these environmental factors observed at the bare stand were reproduced in an assimilation chamber, the rate of photosynthetic CO₂ uptake, stomatal conductance and water potential in leaves were significantly low in comparison with those when the factors at the Q.m. stand were simulated. The internal CO₂ partial pressure in leaves at the bare stand was considerably lower than that at the Q.m. stand. Consequently, the decrease in the photosynthetic rate of the plants at the bare stand was caused mainly by a decrease in stomatal conductance through a lowering of water potential due to subjection of the aboveground parts to much more severe heat stress than that at the Q.m. stand. The possibility that an inhibition of the photosynthetic carbon fixation metabolism induced by the decrease in water potential contributes to the reduction in photosynthetic CO₂ uptake in the plants at the bare stand is also discussed in light of physiological characteristics such as the activity of RuBPcase and levels of PGA, RuBP and sucrose in the leaves.     

Pigment Content of Selected Planktonic Algae in Response to Simulated Natural Light Fluctuations and a Short Photoperiod

The lipophilic photosynthetic pigments in Limnothrix redekei, Planktothrix agardhii (cyanobacteria), Stephanodiscus minutulus, Synedra acus (diatoms), Scenedesmus acuminatus, and Scenedesmus armatus (chlorophycean) all isolated from an eutrophic lake were quantitatively determined by HPLC. The algae were grown semi-continuously under nutrient sufficient conditions at 20°C at a 12/12 h light/dark cycle with constant irradiance or with simulated natural light fluctuations as well as at a 6/18 h light/dark cycle with constant irradiance, all at the same daily light exposure. The zeaxanthin and the myxoxanthophyll contents of cyanobacteria were not influenced by fluctuating light, a short photoperiod or a different sampling time. The chlorophyll b/a ratio, the lutein/chlorophyll a ratio, and the neoxanthin content of chlorophycean as well as the chlorophyll c/a and the fucoxanthin/chlorophyll a ratio of diatoms were only slightly influenced by these factors. Therefore in some cases marker pigment contents and in other cases marker pigment/chlorophyll a ratios may be more useful for quantifying the relative importance of different taxonomic groups in natural phytoplankton. Simulated natural light fluctuations or the length of the photoperiod only slightly influenced the pigment content or the marker pigment/chlorophyll a ratio.     

Egg production rates of the neritic marine copepod Acartia tumida Willey in the Aleutian Archipelago

Acartia tumida, a neritic copepod of the northern North Pacific Ocean and Bering Sea, is an unusually large member of its genus, adult females measuring 2.0–2.4 mm in total length. In the summers of 1986 and 1987 we investigated egg production of A. tumida in nearshore habitats of several islands in the Aleutian Island chain. A. tumida was found within protected embayments, where it could reach adult densities as high as 1000m^–3. Highest egg production rates were measured at Amchitka Island (up to 86 eggs copepod^–1 d^–1 at 6°C), where the phytoplankton was dominated by chain-forming Thalassiosira spp. In situ egg production rates at Amchitka were more than twice as high as maximum rates measured with cultured T. weissflogii, a single cell diatom, or during blooms of chain-forming Chaetoceros spp. at Adak and Kiska Islands. Approximately 12–24 h was necessary for recent feeding to be reflected in egg production. At high food concentrations 75% of spawning occurred at night and in discrete clutches, a pattern not observed at a lower food concentration.     

Integration of repeated sequences (pBR322) in the Bacillus subtilis 168 chromosome without affecting the genome structure

The Escherichia coli plasmid pBR322 sequence (4363 bp) was integrated at the met, pro, or leuB locus of the Bacillus subtilis chromosome without duplication of the flanking chromosomal regions. The integrated pBR322 was stably maintained as part of the chromosome regardless of its orientation or location. It was found that a DNA segment as large as 17 kb cloned in pBR322 can be readily transferred to the B. subtilis chromosome by transformation. It was demonstrated that a second pBR322 sequence could be effectively introduced at different regions of the chromosome by sequential transformation using chromosomal DNA isolated from a strain that had already acquired a pBR322 sequence at a different locus. Similarly, a third pBR322 sequence could be introduced. By this method, two or three pBR322 sequences can be incorporated at unlinked loci without affecting the overall structure of the B. subtilis genome.     

Physiological and fermentation properties of <Emphasis Type="Italic">Bacillus coagulans</Emphasis> and a mutant lacking fermentative lactate dehydrogenase activity

Bacillus coagulans, a sporogenic lactic acid bacterium, grows optimally at 50–55°C and produces lactic acid as the primary fermentation product from both hexoses and pentoses. The amount of fungal cellulases required for simultaneous saccharification and fermentation (SSF) at 55°C was previously reported to be three to four times lower than for SSF at the optimum growth temperature for Saccharomyces cerevisiae of 35°C. An ethanologenic B. coagulans is expected to lower the cellulase loading and production cost of cellulosic ethanol due to SSF at 55°C. As a first step towards developing B. coagulans as an ethanologenic microbial biocatalyst, activity of the primary fermentation enzyme L-lactate dehydrogenase was removed by mutation (strain Suy27). Strain Suy27 produced ethanol as the main fermentation product from glucose during growth at pH 7.0 (0.33 g ethanol per g glucose fermented). Pyruvate dehydrogenase (PDH) and alcohol dehydrogenase (ADH) acting in series contributed to about 55% of the ethanol produced by this mutant while pyruvate formate lyase and ADH were responsible for the remainder. Due to the absence of PDH activity in B. coagulans during fermentative growth at pH 5.0, the l-ldh mutant failed to grow anaerobically at pH 5.0. Strain Suy27-13, a derivative of the l-ldh mutant strain Suy27, that produced PDH activity during anaerobic growth at pH 5.0 grew at this pH and also produced ethanol as the fermentation product (0.39 g per g glucose). These results show that construction of an ethanologenic B. coagulans requires optimal expression of PDH activity in addition to the removal of the LDH activity to support growth and ethanol production.     

Relative Heterothallism and Production of Hybrid Perithecia by Auxotrophic Mutants of Glomerella cingulata from Apple

Glomerella cmgulata is a homothallic species but produces a ridge of fertile perithecia at a frontier between certain wild-type strains on agar. To account for the presence or absence of perithecia earlier workers suggested that alleles at A and B loci control the formation of perithecia at mycelial frontiers in + and – strains. We propose that G. cingulata actually demonstrates “relative heterothallism”. Of 7 induced nutritionally deficient mutants (auxotrophs) in 2 wild-type strains from apple, only one methionine (met-1) and one arginine (arg) mutant in only one wild-type strain gave a heavy ridge of perithecia at their junctures. Neither the met-l nor arg mutations have been identified as those in the A or B locus. The perithecia were either homozygous (selfs) for met-1 or arg, or heterozygous (hybrids). Paired met-1 and arg segregants from hybrid perirhecia as well as diauxotrophic strains from met-l or arg mutants also gave hybrids of selfs. Specific nutritional deficiencies in certain wild-type strains which can direct sexuality are not yet known. Genetic studies are now feasible in G. cingulata to define enzymatic factors responsible for pathogenicity.     

Structure of the multigene family of MAL loci in Saccharomyces

Summary Multigene families are a ubiquitous feature of eukaryotes; however, their presence in Saccharomyces is more limited. The MAL multigene family is comprised of five unlined loci, MAL1, MAL2, MAL3, MAL4 and MAL6, any one of which is sufficient for yeast to metabolize maltose. A cloned MAL6 locus was used as a probe to facilitate the cloning of the other four functional loci as well as two partially active alleles of MAL1. Each locus could be characterized as a cluster of three genes, MALR (regulatory), MALT (maltose transport or permease) and MALS (structural or maltase), encoded by a total of about 7 kb of DNA; however, homologous sequences at each locus extend beyond the coding regions. Our results indicate that there is extensive homology among the MAL loci, especially within their maltase genes. The greatest sequence diversity occurs in their regulatory gene regions. Southern cross analyses of the cloned MAL loci indicate a single duplication of the MAL6R-homologous sequences upstream of the MAL6R gene as well as an extensive duplication of more than 10 kb at the MAL3 locus. The large repeat at the MAL3 locus results in the presence of four copies of MAL3R-homologous sequences and two copies of MAL3T-homologous sequences at that locus. Two naturally occurring inactive alleles of MAL1 show a deletion or divergence of their MALR sequences. The significance of these repeats in the evolution of the MAL multigene family is discussed.     

Identification of Critical Stage for Disease Development and Biocontrol of Alternaria Blight of Indian Mustard (Brassica juncea)

Fungicides mancozeb and carbendazim caused 100% reduction in mycelial growth of Alternaria brassicae over control in vitro while 1% (w/v) aqueous bulb extract of Allium sativum and leaf extract of Acacia nilotica caused significant reductions. In dual culture, GR isolate of Trichoderma viride performed the best among the test isolates of Trichoderma, causing 81%, 82% reduction in mycelial growth of A. brassicae over control. Performance of isolates SI‐2, P and SI‐1 of T. viride were at par (P < 0.01) with that of GR isolate. Spraying of A. brassicae at different ages of the mustard host plant identified 75 days after sowing (d.a.s.) as the most critical age of the mustard plant for development of Alternaria blight severity on the crop with 45 d.a.s. being the next most important one. Mancozeb was the best among all the treatments, resulting in the lowest disease severity on leaves of mustard at both Sewar and Ludhavai as also the lowest A‐value (area under disease progress curve). Performance of bulb extract of A. sativum in checking the disease severity on leaves and pods was at par (P < 0.05) with mancozeb. The GR isolate of T. viride was at par with mancozeb in checking blight severity on mustard leaves at Sewar while performance of the bioagent was significantly (P < 0.05) inferior to the chemical fungicide at Ludhavai. Performance of the bioagent isolate GR of T. viride in checking the disease severity on pods was at par (P < 0.05) with mancozeb at both Sewar and Ludhavai, the treatment recording the lowest A‐value on pods. While application of bulb extract of A. sativum resulted in highest seed yield at Sewar in 2001–2002, the bioagent isolate GR of T. viride did so at Ludhavai, both the treatments being at par (P < 0.05) with mancozeb and significantly higher than control. Application of bulb extract of A. sativum at 45 and 75 d.a.s. resulted in lowest blight severity on leaves and pods as also in highest seed yield among the different single and combination of treatments. Although disease severity in the treatment was at par (P < 0.05) with that in mancozeb, application of the plant extract at the two stages of crop growth resulted in significantly higher seed yield compared with the two applications of the chemical fungicide. However, application of the treatments singly only at 75 d.a.s., GR isolate of T. viride at 45 and 75 d.a.s., A. sativum 45 d.a.s. + T. viride 75 d.a.s., and T. viride 45 d.a.s. + A. sativum 75 d.a.s. resulted in seed yield at par (P < 0.05) with application of bulb extract of A. sativum at 45 and 75 d.a.s.