The effects of mispair and nonpair correction in hybrid DNA on base ratios (G + C content) and total amounts of DNA

Base ratios and total DNA amounts can vary substantially between and within higher taxa and genera, and even within species. Gene conversion is one of several mechanisms that could cause such changes. For base substitutions, disparity in conversion direction is accompanied by an equivalent disparity in base ratio at the heterozygous site. Disparity in the direction of gene conversion at meiosis is common and can be extreme. For transitions (which give purine [R]/pyrimidine [Y] mispairs) and for transversions giving unlike R/R and Y/Y mispairs in hybrid DNA, this disparity could give slow but systematic changes in G + C percentage. For transversions giving like R/R and Y/Y mispairs, it could change AT/TA and CG/GC ratios. From the extent of correction direction disparity, one can deduce properties of repair enzymes, such as the ability (1) to excise preferentially the purine from one mispair and the pyrimidine from the other for two different R/Y mispairs from a single heterozygous site and (2) to excise one base preferentially from unlike R/R or Y/Y mispairs. Frame-shifts usually show strong disparity in conversion direction, with preferential cutting of the nonlooped or the looped-out strand of the nonpair in heterozygous h-DNA. The opposite directions of disparity for frame-shifts and their intragenic suppressors as Ascobolus suggest that repair enzymes have a strong, systematic bias as to which strand is cut. The conversion spectra of mutations induced with different mutagens suggest that the nonlooped strand is preferentially cut, so that base additions generally convert to mutant and deletions generally convert to wild-type forms. Especially in nonfunctional or noncoding DNA, this could cause a general increase in DNA amounts. Conversion disparity, selection, mutation, and other processes interact, affecting rates of change in base ratios and total DNA.      

The toxicity of sulphur dioxide to Diplocarpon rosae Wolf causing blackspot of roses

Germination of conidia of Diplocarpon rosae Wolf is inhibited in a solution made by dissolving 35 p.p.m. sulphur dioxide in water. Inhibition is permanent after exposure for 3 hr. Gaseous SO₂ in air under controlled conditions at 100μg./m³ markedly reduces infection of rose leaves after exposure for 2 days. Blackspot of roses is checked or eliminated in areas where SO₂ pollution of air exceeds 100/μ./m.³.     

Rheumatoid arthritis; an evaluation of long-term treatment with cortisone

Fifty-six patients with rheumatoid arthritis were treated continuously with cortisone for periods ranging between 4 and 38 months, in daily doses of 15 to 100 mg. Concomitant therapy included periods of rest, physical therapy, and salicylates. The incidence of subjective improvement exceeded that of objective improvement. The incidence of objective improvement was higher in females; also, in those patients whose disease was in an early stage and of short duration at the time therapy was begun, and who required relatively smaller maintenance doses of cortisone. Therapeutic results were not affected by the age of the patient or by the presence of spondylitis. Despite precautions, the long-term administration of cortisone was, in some patients, productive of serious undesirable side-effects. Although cortisone usually suppressed the symptoms and signs of rheumatoid arthritis, progression of the disease was frequently noted during its long-term administration.     

Homogeneity of the 16S rDNA sequence among geographically disparate isolates of Taylorella equigenitalis

Background

At present, six accessible sequences of 16S rDNA from Taylorella equigenitalis (T. equigenitalis) are available, whose sequence differences occur at a few nucleotide positions. Thus it is important to determine these sequences from additional strains in other countries, if possible, in order to clarify any anomalies regarding 16S rDNA sequence heterogeneity. Here, we clone and sequence the approximate full-length 16S rDNA from additional strains of T. equigenitalis isolated in Japan, Australia and France and compare these sequences to the existing published sequences.

Results

Clarification of any anomalies regarding 16S rDNA sequence heterogeneity of T. equigenitalis was carried out. When cloning, sequencing and comparison of the approximate full-length 16S rDNA from 17 strains of T. equigenitalis isolated in Japan, Australia and France, nucleotide sequence differences were demonstrated at the six loci in the 1,469 nucleotide sequence. Moreover, 12 polymorphic sites occurred among 23 sequences of the 16S rDNA, including the six reference sequences.

Conclusion

High sequence similarity (99.5% or more) was observed throughout, except from nucleotide positions 138 to 501 where substitutions and deletions were noted.     

Temporal Variation in Seed Predation by Insects in a Population of Syagrus romanzoffiana (Arecaceae) in Santa Catarina Island, SC, Brazil

Insect seed predation may vary depending on seed production. The present study considers the hypothesis that the rates of seed predation tend to be smaller in years of higher fruit production. Thus, we monitored the production of fruits and predation of seeds of the palm Syagrus romanzoffiana over 2?years in the Atlantic Forest (Parque Municipal da Lagoa do Peri, Florianópolis, SC, Brazil), between July 2006 and June 2008. Plots of 0.25?m² were fitted under 20 mother plants and fruits were monthly collected for assessment of abundance and seed predation. There was variation in fruit production between the 2?years and among reproductive plants. Predation rates were high and occurred in the predispersal phase by the Curculionidae Revena rubiginosa Boheman, Anchylorhynchus aegrotus Fahraeus, and Anchylorhynchus variabilis Gyllenhal. Seed predation by these species of Anchylorhynchus is first registered in the present study. In average, about 60% of the seeds monthly produced in the population tend to escape insect predation in year of high or low production, becoming available for recruitment. The predation rate was not related to the amount of fruits produced per reproductive plant. Also, different than expected, there was a positive relation between the rates of seed predation and the total of fruits produced monthly on the plots. Thus, no evidence for the satiation of insect seed predators was found in this study with S. romanzoffiana.     

A synopsis of Goniothalamus species (Annonaceae) in Thailand, with descriptions of three new species

A comprehensive taxonomic revision of Goniothalamus species (Annonaceae) occurring in Thailand is presented for the first time. Twenty-five species are recognized, including three that are described as new to science ( Goniothalamus aurantiacus from South-Western Thailand, Goniothalamus maewongensis from Northern Thailand, and Goniothalamus rongklanus from Northern and North-Eastern Thailand). Several taxonomic and nomenclatural misunderstandings are corrected. The name G. griffithii is shown to be widely misapplied for populations in Northern Thailand, for which the name G. calvicarpus should be applied; 'true' G. griffithii is restricted to South-Western Thailand and Myanmar. In addition, the widely used name G. marcanii is shown to be a synonym of G. tamirensis , and the name G. latestigma , previously regarded as a synonym of G. undulatus , is reinstated. Goniothalamus cheliensis is furthermore newly recorded from Thailand. Most species are restricted to Peninsular Thailand and represent a Malesian floristic component.  © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society , 2008, 156 , 355–384.