Journal of Molecular Evolution最新文献

In this research paper, I provided a comprehensive overview of "Chemosensory Proteins" (CSPs), which have traditionally been thought to be involved in transporting odorant or tastant molecules to chemosensory receptors. However, CSPs are perplexingly expressed in various other organs and likely serve purposes other than chemosensing. By searching against microbial and crustacean protein databases, I found that CSPs are present not only in insects and other arthropods but also in bacteria. Given that CSPs are present from prokaryotes to insects and arthropods, and are expressed in many various tissues, I came to the conclusion that CSPs are unlikely to have purely chemosensory functions. This is consistent with most recent findings in the chemosensory field of Drosophila, where CSPs and odorant-binding proteins are thought to have functions beyond acting as odorant/tastant binding molecules.

Carbohydrate sulfotransferases (CHSTs) play a vital role in the production of sulfated polysaccharides (SPs) in algae by catalyzing the sulfation of carbohydrate moieties through the transfer of a sulfuryl group from the donor, 3'-phosphoadenosine 5'-phosphosulfate (PAPS). In the present study, putative algal CHSTs with a PF00685, PF03567. PF06990 and PF13469 domain were identified by HMMER search and Protein Basic Local Alignment Search Tool (BLAST) using the well-characterized human CHSTs as queries. Approximately half of the algal CHSTs that contained a PF00685 domain also possessed a PF13469 domain in an overlapping region. These CHSTs were structurally and phylogenetically distinct from algal CHSTs containing PF03567 or/and PF06990 domains. The PF00685/PF13469 domain is commonly found in Chlorophyta, while PF03567 and PF06990 domains are more prevalent in red algae and brown algae, respectively, reflecting the different types of SPs produced by these distinct phyla. Our phylogenetic analyses of algal CHSTs support the hypothesis of a polyphyletic origin, suggesting complex evolutionary histories involving both lineage-specific evolution and significant horizontal gene transfer (HGT) events between algae and organisms from other diverse taxa, including bacteria. In addition, the specificities of algal CHSTs for different carbohydrate moieties and site-specific sulfation patterns were inferred from the phylogenies of human CHSTs and the CHSTs from of algae with known SPs and chemical structures. This approach helps us to bridge the gap in knowledge, as a limited number of algal CHSTs have been biochemically characterized experimentally.

The phylogeny of a person's hematopoietic stem cells (HSCs) can be used to quantify physiological aging of blood using a phyloAge model based on diversity decay metrics. However, this procedure currently requires accurate HSC genome sequences, which are expensive and time-consuming to obtain. We show that metrics of diversity decay can be derived from the somatic variant frequency spectrum (VFS) using more affordable, routine bulk sequencing, because HSCs evolve without recombination at a clock-like rate. We found that VFS-based models produce phyloAge estimates similar to those derived from HSC genome phylogenies. Customized for protein-coding variation and sequencing read depth, VFS-based HSC phyloAge estimates were, on average, 168 years more than chronological ages in 157 patients with acute myeloid leukemia, consistent with excess HSC aging observed in cancer patients using single cell genome phylogenies. We also tested the hypothesis that variants in cancer driver genes may confer longevity, as they occur in a significant fraction of long-lived individuals. Indeed, HSC phyloAge estimates were significantly lower, consistent with reduced hematologic cancer risk among extremely old individuals. Thus, the new metrics and models broaden the utility of the phyloAge approach, making it feasible and efficient for clinical and research applications.

DNA codon mutations involving Stop signals or the amino acid cysteine can be especially damaging. The former can break protein sequences or add extraneous amino acids. The latter can add or subtract disulfide bonds crucial in protein folding. We present a hypothetical scenario where Stop codons were present early in the evolution of the genetic code; and minimizing catastrophic mutations for code networks affected all subsequent amino acid/codon pairings. Predicted features of this "Catastrophic Mutation Minimization Hypothesis" (CMMH) are that: (1) Cysteine is mutationally adjacent to Stop, isolating a contiguous codon 'neighborhood' with high potential for catastrophe. (2) The sequence of amino acid additions order determines codon assignments through minimizing network-wide mutation costs. Overall, codon locations for 16 of the 20 amino acids in the genetic code are consistent with the CMMH, as are multiple other predictions. We propose an antecedent genetic code consisted of 16 doublet codons specifying 13-14 amino acids. Two variations of these networks are less susceptible to catastrophic mutations than 88.2-97.5% of randomly generated ones. Unlike some previous hypotheses, CMMH does not require the total replacement or rearrangement of amino acids at codons, with its disruptive potential for protein synthesis. Finally, the composition of this ancestral doublet genetic code has all the modern code's utility: amino acids from four chemical types; start and stop signals; metal-binding ability; disulfide bridging for creating protein shapes; and possible epigenetic gene regulation. Thus, the modern code likely evolutionarily fine-tuned antecedent capabilities, rather than significantly increasing competence for making complex proteins.

The adaptation to terrestrial environments from aquatic environments has always been regarded as a major evolutionary transition in fishes, during which it has been accompanied with diverse phenotypic innovations. Mitochondrial energy metabolism fundamentally enables this shift, but the evolutionary trajectory and molecular mechanisms of mitogenomic adaptations to energy demands are poorly characterized. Mudskippers, a group of gobies with amphibious adaptive traits, serve as ideal models for studying energy metabolism during the water-to-land transition. To test whether amphibious adaptation in gobies corresponds to adaptive evolution in mitochondrial OXPHOS genes, we performed an in silico analysis of the 13 OXPHOS genes from the mitochondrial genomes of 33 goby species and two outgroups. The results showed that: (1) No matter ML or BI methods, four subfamilies Amblyopinae, Gobiinae, Gobionellinae, Oxudercinae are paraphyletic origin, except for subfamily Sicydiinae; besides, genus Scartelaos was first confirmed that it is paraphyletic origin. (2) 13 OXPHOS genes have been under the strong selective constraints, yet, the episodic positive selection was also detected, and ND4 and ATP8 evolution has been found to be under the accelerated evolution. Interestingly, (3) Significant divergent selection was detected between amphibious and fully aquatic lineages in 11 of the 13 OXPHOS genes (84%). And (4) the much stronger selective constraints were uncovered in amphibious lineages. To sum up, OXPHOS genes have undergone adaptive evolution with notable divergent patterns associated with the water-to-land transition during transition from water to land. These results provided some new insights into the genetic basis of amphibious adaptation in goby.