The Baker's Yeast Diploid Genome Is Remarkably Stable in Vegetative Growth and Meiosis

Accurate estimates of mutation rates provide critical information to analyze genome evolution and organism fitness. We used whole-genome DNA sequencing, pulse-field gel electrophoresis, and comparative genome hybridization to determine mutation rates in diploid vegetative and meiotic mutation accumulation lines of Saccharomyces cerevisiae. The vegetative lines underwent only mitotic divisions while the meiotic lines underwent a meiotic cycle every ∼20 vegetative divisions. Similar base substitution rates were estimated for both lines. Given our experimental design, these measures indicated that the meiotic mutation rate is within the range of being equal to zero to being 55-fold higher than the vegetative rate. Mutations detected in vegetative lines were all heterozygous while those in meiotic lines were homozygous. A quantitative analysis of intra-tetrad mating events in the meiotic lines showed that inter-spore mating is primarily responsible for rapidly fixing mutations to homozygosity as well as for removing mutations. We did not observe 1–2 nt insertion/deletion (in-del) mutations in any of the sequenced lines and only one structural variant in a non-telomeric location was found. However, a large number of structural variations in subtelomeric sequences were seen in both vegetative and meiotic lines that did not affect viability. Our results indicate that the diploid yeast nuclear genome is remarkably stable during the vegetative and meiotic cell cycles and support the hypothesis that peripheral regions of chromosomes are more dynamic than gene-rich central sections where structural rearrangements could be deleterious. This work also provides an improved estimate for the mutational load carried by diploid organisms

Convergent aspects of acoustic communication in darters, sculpins and gobies

Darters (Perciformes, Percidae), sculpins (Perciformes, Cottidae), and gobioids (Gobiiformes, Gobioidei) exhibit convergent life history traits, including a benthic lifestyle and a cavity nesting spawning mode. Soniferous species within these taxa produce pulsed and/or tonal sounds with peak frequencies below 200 Hz (with some exceptions), primarily in agonistic and/or reproductive contexts. The reduced or absent swim bladders found in these taxa limit or prevent both hearing enhancement via pressure sensitivity and acoustic amplification of the contracting sonic muscles, which are associated with the skull and pectoral girdle. While such anatomies constrain communication to low frequency channels, optimization of the S/N (signal-to-noise) ratio in low frequency channels is evident for some gobies, as measured by habitat soundscape frequency windows, nest cavity sound amplification, and audiograms. Similar S/N considerations are applicable to many darter and sculpin systems. This chapter reviews the currently documented diversity of sound production in darters, sculpins, and gobioids within a phylogenetic context, examines the efficacy of signal transmission from senders to receivers (sound production mechanisms, audiograms, and masking challenges), and evaluates the potential functional significance of sound attributes in relation to territorial and reproductive behaviours