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Cytoplasmic and mitochondrial forms of a eukaryotic aminoacyl-tRNA synthetase (aaRS) are generally encoded by two distinct nuclear genes, one of eukaryotic origin and the other of mitochondrial origin. However, in most known yeasts, only the mitochondrial- origin alanyl-tRNA synthetase (AlaRS) gene is retained and plays a dual-functional role. Here, we present a novel scenario of AlaRS evolution in the yeast Vanderwaltozyma polyspora. V. polyspora possesses two significantly diverged AlaRS gene homologues, one encoding the cytoplasmic form and the other its mitochondrial counterpart. Clever selection of transcription and translation initiation sites enables the two isoforms to be localized and thus functional in their respective cellular compartments. However, the two isoforms can also be stably expressed and function in the reciprocal compartments by insertion or removal of a mitochondrial targeting signal. Synteny and phylogeny analyses revealed that the AlaRS homologues of V. polyspora arose from a dual-functional common ancestor through whole-genome duplication (WGD). Moreover, the mitochondrial form had higher synonymous (1.6-fold) and nonsynonymous (2.8-fold) substitution rates than did its cytoplasmic counterpart, presumably due to a lesser constraint imposed on components of the mitochondrial translational apparatus. Our study suggests that asymmetric evolution confers the divergence between the AlaRS paralogues of V. polyspora. [ABSTRACT FROM AUTHOR]

The study explores whether the visual abilities of Taiwan's closely related bitterlings, Paratanakia himantegus himantegus and Paratanakia himantegus chii, correspond with their habitats' photic parameters and correlate with nuptial colorations. Topics covered include the subspecies' different visual spectral sensitivities and nuptial coloration, their habitats' ambient light spectra, and potential role of ultra violet (UV) light in the fishes' visual communication and gender identification.

The article discusses a study which analyzed the phylogeny of freshwater eel Anguilla huangi, which were collected from the Cagayan River estuary, Northern Luzon, Philippines. The freshwater eels were reared in Taiwan for five years. The complete mitochondrial genome of the ell was sequences and a phylogeny of all freshwater eel species and subspecies was created using molecular and morphological information. Study authors concluded that the phylogeny of freshwater eels is better represented by polytomies, that are derived from multiple radiation.

Many Saccharomyces cerevisiae duplicate genes that were derived from an ancient whole-genome duplication (WGD) unexpectedly show a small synonymous divergence (Ks), a higher sequence similarity to each other than to orthologues in Saccharomyces bayanus, or slow evolution compared with the orthologue in Kluyveromyces waltii, a non-WGD species. This decelerated evolution was attributed to gene conversion between duplicates. Using ≈300 WGD gene pairs in four species and their orthologues in non-WGD species, we show that codon-usage bias and protein-sequence conservation are two important causes for decelerated evolution of duplicate genes, whereas gene conversion is effective only in the presence of strong codon-usage bias or protein-sequence conservation. Furthermore, we find that change in mutation pattern or in tDNA copy number changed codon-usage bias and increased the Ks distance between K. waltii and S. cerevisiae. Intriguingly, some proteins showed fast evolution before the radiation of WGD species but little or no sequence divergence between orthologues and paralogues thereafter, indicating that functional conservation after the radiation may also be responsible for decelerated evolution in duplicates. [ABSTRACT FROM AUTHOR]

Lin, Y.-S., Tzeng, C.-S.&Hwang, J.-K. (2005). Reassessment of morphological characteristics in freshwater eels (genusAnguilla, Anguillidae) shows congruence with molecular phylogeny estimates.— Zoologica Scripta,34, 225–234.The morphology-based phylogeny of freshwater eels, proposed by V. Ege in 1939, has been accepted as the basis of eel classification since that time. However, this has been called into question by recent molecular studies. Most of the morphological characteristics recognized by Ege are morphometric. Since methods for the application of morphometric data to phylogeny construction have not been fully established, it is unclear whether the observed discrepancies between morphological and molecular data arise from intrinsic differences or from flawed analyses. Here, we have used two methods to assemble evolutionary trees from distance matrices constructed according to Ege's data, the neighbor-joining (NJ) method and the minimum network (MinNet) method; the latter is based on an evolutionary algorithm. After reanalysing Ege's morphological data, we found that both methods gave results consistent with those based on molecular data, although not with Ege's original classification. Therefore, we speculate that some morphological features Ege used to subdivide the eel groups may not be synapomorphic as he proposed, but symplesiomorphic or convergent . The method developed here may prove useful for constructing phylogeny for taxon groups where only continuous morphometric characteristics are recognized, such as the freshwater eels. [ABSTRACT FROM AUTHOR]