Phylogeny of Greya (Lepidoptera: Prodoxidae), based on nucleotide sequence variation in mitochondrial cytochrome oxidase I and II: congruence with morphological data

The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from nucleotide sequence variation across a 765-bp region in the cytochrome oxidase I and II genes of the mitochondrial genome. Most parsimonious relationships of 25 haplotypes from 16 Greya species and two outgroup genera (Tetragma and Prodoxus) showed substantial congruence with the species relationships indicated by morphological variation. Differences between mitochondrial and morphological trees were found primarily in the positions of two species, G. variabilis and G. pectinifera, and in the branching order of the three major species groups in the genus. Conflicts between the data sets were examined by comparing levels of homoplasy in characters supporting alternative hypotheses. The phylogeny of Greya species suggests that host-plant association at the family level and larval feeding mode are conservative characters. Transition/transversion ratios estimated by reconstruction of nucleotide substitutions on the phylogeny had a range of 2.0-9.3, when different subsets of the phylogeny were used. The decline of this ratio with the increase in maximum sequence divergence among taxa indicates that transitions are masked by transversions along deeper internodes or long branches of the phylogeny. Among transitions, substitutions of A-->G and T-->C outnumbered their reciprocal substitutions by 2-6 times, presumably because of the approximately 4:1 (77%) A+T-bias in nucleotide base composition. Of all transversions, 73%-80% were A<-->T substitutions, 85% of which occurred at third positions of codons; these estimates did not decrease with an increase in maximum sequence divergence of taxa included in the analysis. The high frequency of A<-->T substitutions is either a reflection or an explanation of the 92% A+T bias at third codon positions.      

Glycoproteins of measles virus under reducing and nonreducing conditions.

Measles virus has two glycoproteins. The larger glycoprotein (HA) is composed of 76,000-dalton subunits that are bound by disulfide bonds. The smaller glycoprotein (F) appears to contain a glucosamine-rich portion that is linked to an unglycosylated protein by disulfide bonds.     

Leaves of the Arabidopsis?maltose exporter1?Mutant Exhibit a?Metabolic Profile with?Features of Cold Acclimation in the Warm

Background

Arabidopsis plants accumulate maltose from starch breakdown during cold acclimation. The Arabidopsis mutant, maltose excess1-1, accumulates large amounts of maltose in the plastid even in the warm, due to a deficient plastid envelope maltose transporter. We therefore investigated whether the elevated maltose level in mex1-1 in the warm could result in changes in metabolism and physiology typical of WT plants grown in the cold.

Principal Findings

Grown at 21 °C, mex1-1 plants were much smaller, with fewer leaves, and elevated carbohydrates and amino acids compared to WT. However, after transfer to 4 °C the total soluble sugar pool and amino acid concentration was in equal abundance in both genotypes, although the most abundant sugar in mex1-1 was still maltose whereas sucrose was in greatest abundance in WT. The chlorophyll a/b ratio in WT was much lower in the cold than in the warm, but in mex1-1 it was low in both warm and cold. After prolonged growth at 4 °C, the shoot biomass, rosette diameter and number of leaves at bolting were similar in mex1-1 and WT.

Conclusions

The mex1-1 mutation in warm-grown plants confers aspects of cold acclimation, including elevated levels of sugars and amino acids and low chlorophyll a/b ratio. This may in turn compromise growth of mex1-1 in the warm relative to WT. We suggest that elevated maltose in the plastid could be responsible for key aspects of cold acclimation.     

Analysis of plastid DNA-like sequences within the nuclear genomes of higher plants

A wide-ranging examination of plastid (pt)DNA sequence homologies within higher plant nuclear genomes (promiscuous DNA) was undertaken. Digestion with methylation-sensitive restriction enzymes and Southern analysis was used to distinguish plastid and nuclear DNA in order to assess the extent of variability of promiscuous sequences within and between plant species. Some species, such as Gossypium hirsutum (cotton), Nicotiana tabacum (tobacco), and Chenopodium quinoa, showed homogenity of these sequences, while intraspecific sequence variation was observed among different cultivars of Pisum sativum (pea), Hordeum vulgare (barley), and Triticum aestivum (wheat). Hypervariability of plastid sequence homologies was identified in the nuclear genomes of Spinacea oleracea (spinach) and Beta vulgaris (beet), in which individual plants were shown to possess a unique spectrum of nuclear sequences with ptDNA homology. This hypervariability apparently extended to somatic variation in B. vulgaris. No sequences with ptDNA homology were identified by this method in the nuclear genome of Arabidopsis thaliana.      

Above- and below-ground responses of Calamagrostis purpurea to UV-B radiation and elevated CO₂ under phosphorus limitation

UV-B radiation and elevated CO? may impact rhizosphere processes through altered below-ground plant resource allocation and root exudation, changes that may have implications for nutrient acquisition. As nutrients limit plant growth in many habitats, their supply may dictate plant response under elevated CO?. This study investigated UV-B exposure and elevated CO? effects, including interactions, on plant growth, tissue chemistry and rooting responses relating to P acquisition. The sub-arctic grass Calamagrostis purpurea was subjected to UV-B (0 or 3.04 kJ m?2 day?1) and CO? (ambient 380 or 650 ppmv) treatments in a factorial glasshouse experiment, with sparingly soluble P (0 or 0.152 mg P per plant as FePO?) a further factor. It was hypothesized that UV-B exposure and elevated CO?would change plant resource allocation, with CO? mitigating adverse responses to UV-B exposure and aiding P uptake. Plant biomass and morphology, tissue composition and rhizosphere leachate properties were measured. UV-B directly affected chemical composition of shoots and interacted with CO? to give a greater root biomass. Elevated CO? altered the composition of both shoots and roots and increased shoot biomass and secondary root length, while leachate pH decreased. Below-ground responses to CO? did not affect P acquisition although P limitation progressively reduced leachate pH and increased secondary root length. Although direct plant growth, foliar composition and below-ground nutrient acquisition responses were dominated by CO? treatments, UV-B modified these CO? responses significantly. These interactions have implications for plant responses to future atmospheric conditions.     

Comparison of the relative biological availability and stability of commercial sources of vitamin K activity

In a test designed to examine the stability and biological availability of different sources of menadione available to the feed industry, encapsulated menadione sodium bisulphite (Kastab) and menadione dimethylpyrimidinol bisulphite appeared to be relatively equal in both stability under steam pelleting and biological availability as measured by chick prothrombin times. Menadione sodium bisulphite complex did not appear to be as biologically available but possessed equal stability under pelleting. Particle size of all supplements was similar, suggesting no probable differences in distribution into the feed. The data from this study support the current National Research Council suggestion of 400 μg of menadione activity per kg of diet.     

Measles Virus Ribonucleic Acid and Protein Synthesis: Effects of 6-Azauridine and Cycloheximide on Viral Replication

Cycloheximide and 6-azauridine were employed to study the time course of measles virus protein and nucleic acid syntheses in AV3 cells. Synthesis of ribonucleic acid (RNA) essential for infectivity was first detected at 6 hr and increased concurrently with the formation of essential protein. Maximum levels of virus-specific RNA and protein were present by 18 hr, a time when only 5% of progeny virus was detected. Essential RNA and protein syntheses preceded the formation of infectious virus by at least 10 to 12 hr. The time course of RNA and protein syntheses essential for the formation of complement-fixing (CF) antigen and salt-dependent agglutinin (SDA) was also determined. RNA synthesis essential for the formation of SDA was first detected at 2 hr and was present maximally by 6 hr, whereas SDA-protein increased concurrently with the protein essential for infectivity. This suggested that the last protein essential for infectivity may be SDA. RNA synthesis essential for the formation of CF antigen was first detected at 4 hr, while CF-protein increased at 5 hr and preceded SDA-protein and protein essential for infectivity by approximately 3 hr. Reversal of inhibition of protein synthesis by cycloheximide indicated that early protein synthesis (1 to 3 hr) was required for the formation of infectious virus. The data suggest that the relatively long eclipse period observed with measles virus is related to a long maturation period rather than to late formation of early proteins, viral RNA, or structural proteins.