Integrative biology and genetic resources management.

Integrative Biology is exemplified by a diversity of recently established collaborations to study the genetic diversity of the European rabbit, Oryctolagus cuniculus. Molecular markers were developed and used to investigate the link between wild population decreases or domestication procedures and possible losses of genetic diversity. Simultaneously, a European programme was launched for the management of genetic resources.

Different levels of human intervention in domestic rabbits: effects on genetic diversity.

The effects of human interaction on domestic rabbits were evaluated through the analysis of animals (up to 267) belonging to fancy breeds (22), a commercial breed (1), and selected strains (2). Microsatellite loci and mtDNA polymorphism revealed that the genetic pool of domestic rabbits studied only originated from that available in France. The good conservation of the original diversity was probably ensured through the multiplicity of samplings from wild populations.

Mitochondrial genes collectively suggest the paraphyly of Crustacea with respect to Insecta.

Complete sequences of seven protein coding genes from Penaeus notialis mitochondrial DNA were compared in base composition and codon usage with homologous genes from Artemia franciscana and four insects. The crustacean genes are significantly less A + T-rich than their counterpart in insects and the pattern of codon usage (ratio of G + C-rich versus A + T-rich codon) is less biased. A phylogenetic analysis using amino acid sequences of the seven corresponding polypeptides supports a sister-taxon status for mollusks-annelid and arthropods.

Nonneutral evolution of tandem repeats in the mitochondrial DNA control region of lagomorphs.

The mitochondrial DNA of the European rabbit (Oryctolagus cuniculus) contains a tandem array of 153-bp repeats in the vicinity of the replication origin of the H-stand. Variation among molecules in the number of these repeats results in inter- and intraindividual length polymorphism (heteroplasmy). Generally, in an individual, one predominant molecular type is observed, the others representing a low percentage of the mtDNA content.

Partial sequence of the shrimp Penaeus notialis mitochondrial genome.

About half of the mitochondrial DNA of the shrimp Penaeus notialis (Crustacea: Decapoda) has been cloned (in 2 overlapping fragments of 7.9 kb and 1 kb) and partially sequenced. The gene content and arrangement are identical to that of the homologous domain in Drosophila yakuba.

Rabbit mitochondrial DNA diversity from prehistoric to modern times.

The mitochondrial genetic variability in European rabbit (Oryctolagus cuniculus) populations present in Europe and North Africa from 11,000 years ago to the present day has been analyzed using ancient DNA techniques. DNA was extracted from 90 rabbit bones found in 22 archaeological sites dated between the Mesolithic and recent times. Nucleotide sequences present in a variable 233-bp domain of the cytochrome b gene were compared to those present in modern-day rabbits.

Genetic analysis of systematic mitochondrial heteroplasmy in rabbits.

One unusual property of rabbit mitochondrial DNA (mtDNA) is the existence of repeated 153-bp motifs in the vicinity of the replication origin of its H strand. Furthermore, every individual is heteroplasmic: it carries mtDNA molecules with a variable number of repeats. A systematic study of 8 females and their progeny has been devised to analyze mtDNA transmission through generations.

Ancient DNA from Bronze Age bones of European rabbit (Oryctolagus cuniculus).

The European rabbit (Oryctolagus cuniculus) is now widely distributed throughout the world as a result of transportation by man. The original populations, however, were confined to southern France and Spain. In order to investigate the role of human intervention in determining the genetic diversity of rabbit populations, we are studying the origin of rabbits introduced onto a small Mediterranean island (Zembra) near Tunis over 1400 years ago, by examining ancient DNA extracted from rabbit bones found both on Zembra and on the European mainland.

Mitochondrial DNA variability in Drosophila simulans: quasi absence of polymorphism within each of the three cytoplasmic races.

Nucleotide variability of mtDNA extracted from 144 isofemale lines collected in the whole range of D. simulans was analysed with 10-15 restriction enzymes and 73 lines were studied using one or a few enzymes. All clones were distributed into 3 mitochondrial genomes, siI, siII and siIII.

Co-linear organization of Xenopus laevis and mouse mitochondrial genomes.

Cloned fragments of Xenopus laevis mitochondrial DNA and Pleurodeles waltlii mitochondrial cDNAs have been hybridized together and with mouse mtDNA. In the three cases cross-hybridization was observed. The overall organization of the X.

Changes in D-loop frequency and superhelicity among the mitochondrial DNA molecules in relation to organelle biogenesis in oocytes of Xenopus laevis.

Changes in mitochondrial DNA (mtDNA) replication activity are known to occur during oogenesis in Xenopus laevis. Electron microscopic and electrophoretic analyses carried out on mtDNA molecules at different vitellogenic stages show that 1. The frequency of displacement loop (D-loop) forms is correlated with the intensity of mitochondrial biogenesis.

Development of the mitochondrial mass and accumulation of mtDNA in previtellogenic stages of Xenopus laevis oocytes.

The development of the mitochondrial mass of the previtellogenic oocytes of Xenopus laevis has been analysed by a morphometric method and it has been correlated with the growth of the occyte itself. The study which was performed with oocytes from females of very different ages shows that the relative size of the mitochondrial mass in the smallest oocytes decreases gradually with the age of the females. Cytophotometric analysis of the Feulgen-stained mitochondrial mass enabled the mtDNA content of that structure to be quantified during its development.

KINETIC ANALYSIS OF ENTIRE OOGENESIS IN XENOPUS LAEVIS.

In our breeding conditions (without artificial hormonal stimulation) two years after metamorphosis are necessary for a Xenopus laevis female to produce mature oocytes. Four periods of different growth rates can be distinguished into this first wave of oogenesis: 1) oocytes reach 120 μm in diameter (early stage I according to Dumont (5)) in a few weeks after metamorphosis; 2) growth slows down and the size of 250-300 μm (late stage I) is obtained 6-7 months later; 3) a rapid growth resumes during vitellogenesis (stages II, III and IV) and a 1,000-1,100 μm diameter is reached in 2-3 months; 4) the last period spans for a year and the oocyte grows up to 1,200 μm. This phase covers many physiological changes and it should be critical to size carefully the oocytes for biochemical investigations and comparisons.

Inserted sequence in the mitochondrial 23S ribosomal RNA gene of the yeast Saccharomyces cerevisiae.

The sequence organization of the yeast mit-DNA region carrying the large ribosomal RNA gene and the polar locus omega was examined. Hybridization studies using rho- deletion mutants and electron microscopy of the heteroduplexes formed between 23S rRNA and the appropriate restriction fragments, lead to the conclusion that the 23S rRNA1 gene of the omega+ strains is split by an insertion sequence of 1,000-1,100 bp. In contrast, no detactable insertion was found in the 23S rRNA gene of the omega- strains.