Inferring Positional Homologs with Common Intervals of Sequences

International audienceInferring orthologous and paralogous genes is an important problem in whole genomes comparisons, both for functional or evolutionary studies. In this paper, we introduce a new approach for inferring candidate pairs of orthologous genes between genomes, also called positional homologs, based on the conservation of the genomic context. We consider genomes represented by their gene order -- i.e. sequences of signed integers -- and common intervals of these sequences as the anchors of the final gene matching. We show that the natural combinatorial problem of computing a maximal cover of the two genomes using the minimum number of common intervals is NP-complete and we give a simple heuristic for this problem. We illustrate the effectiveness of this first approach using common intervals of sequences on two datasets, respectively 8 $\gamma$-proteobacterial genomes and the human and mouse whole genomes

Cardiorespiratory performance during prolonged swimming tests with salmonids: a perspective on temperature effects and potential analytical pitfalls

A prolonged swimming trial is the most common approach in studying steady-state changes in oxygen uptake, cardiac output and tissue oxygen extraction as a function of swimming speed in salmonids. The data generated by these sorts of studies are used here to support the idea that a maximum oxygen uptake is reached during a critical swimming speed test. Maximum oxygen uptake has a temperature optimum. Potential explanations are advanced to explain why maximum aerobic performance falls off at high temperature. The valuable information provided by critical swimming tests can be confounded by non-steady-state swimming behaviours, which typically occur with increasing frequency as salmonids approach fatigue. Two major concerns are noted. Foremost, measurements of oxygen uptake during swimming can considerably underestimate the true cost of transport near critical swimming speed, apparently in a temperature-dependent manner. Second, based on a comparison with voluntary swimming ascents in a raceway, forced swimming trials in a swim tunnel respirometer may underestimate critical swimming speed, possibly because fish in a swim tunnel respirometer are unable to sustain a ground speed