Coevolution of Interacting Fertilization Proteins

Reproductive proteins are among the fastest evolving in the proteome, often due to the consequences of positive selection, and their rapid evolution is frequently attributed to a coevolutionary process between interacting female and male proteins. Such a process could leave characteristic signatures at coevolving genes. One signature of coevolution, predicted by sexual selection theory, is an association of alleles between the two genes. Another predicted signature is a correlation of evolutionary rates during divergence due to compensatory evolution. We studied female–male coevolution in the abalone by resequencing sperm lysin and its interacting egg coat protein, VERL, in populations of two species. As predicted, we found intergenic linkage disequilibrium between lysin and VERL, despite our demonstration that they are not physically linked. This finding supports a central prediction of sexual selection using actual genotypes, that of an association between a male trait and its female preference locus. We also created a novel likelihood method to show that lysin and VERL have experienced correlated rates of evolution. These two signatures of coevolution can provide statistical rigor to hypotheses of coevolution and could be exploited for identifying coevolving proteins a priori. We also present polymorphism-based evidence for positive selection and implicate recent selective events at the specific structural regions of lysin and VERL responsible for their species-specific interaction. Finally, we observed deep subdivision between VERL alleles in one species, which matches a theoretical prediction of sexual conflict. Thus, abalone fertilization proteins illustrate how coevolution can lead to reproductive barriers and potentially drive speciation

Molecular population genetics of the gene encoding the human fertilization protein zonadhesin reveals rapid adaptive evolution

A hallmark of positive selection (adaptive evolution) in protein-coding regions is a dN/dS ratio >1, where dN is the number of nonsynonymous substitutions/nonsynonymous sites and dS is the number of synonymous substitutions/synonymous sites. Zonadhesin is a male reproductive protein localized on the sperm head, comprising many domains known to be involved in cell-cell interaction or cell adhesion. Previous studies have shown that VWD domains (homologous to the D domains of the von Willebrand factor) are involved directly in binding to the female zona pellucida (ZP) in a species-specific manner. In this study, we sequenced 47 coding exons in 12 primate species and, by using maximum-likelihood methods to determine sites under positive selection, we show that VWD2, membrane/A5 antigen mu receptor, and mucin-like domains in zonadhesin are rapidly evolving and, thus, may be involved in binding to the ZP in a species-specific manner in primates. In addition, polymorphism data from 48 human individuals revealed significant polymorphism-to-divergence heterogeneity and a significant departure from equilibrium-neutral expectations in the frequency spectrum, suggesting balancing selection and positive selection occurring in zonadhesin (ZAN) within human populations. Finally, we observe adaptive evolution in haplotypes segregating for a frameshift mutation that was previously thought to indicate that ZAN was a potential pseudogene

Essential gene deletions producing gigantic bacteria.

To characterize the consequences of eliminating essential functions needed for peptidoglycan synthesis, we generated deletion mutations of Acinetobacter baylyi by natural transformation and visualized the resulting microcolonies of dead cells. We found that loss of genes required for peptidoglycan precursor synthesis or polymerization led to the formation of polymorphic giant cells with diameters that could exceed ten times normal. Treatment with antibiotics targeting early or late steps of peptidoglycan synthesis also produced giant cells. The giant cells eventually lysed, although they were partially stabilized by osmotic protection. Genome-scale transposon mutant screening (Tn-seq) identified mutations that blocked or accelerated giant cell formation. Among the mutations that blocked the process were those inactivating a function predicted to cleave murein glycan chains (the MltD murein lytic transglycosylase), suggesting that giant cell formation requires MltD hydrolysis of existing peptidoglycan. Among the mutations that accelerated giant cell formation after ß-lactam treatment were those inactivating an enzyme that produces unusual 3->3 peptide cross-links in peptidoglycan (the LdtG L,D-transpeptidase). The mutations may weaken the sacculus and make it more vulnerable to further disruption. Although the study focused on A. baylyi, we found that a pathogenic relative (A. baumannii) also produced giant cells with genetic dependencies overlapping those of A. baylyi. Overall, the analysis defines a genetic pathway for giant cell formation conserved in Acinetobacter species in which independent initiating branches converge to create the unusual cells

The effect of anticancer drugs on seven cell lines monitored by FTIR spectroscopy.

Systemic approaches such as metabolomics are increasingly needed to improve the development of novel drugs. In this paper, we suggest a new strategy based on infrared spectroscopy which probes the global chemical composition of a sample. Seven cell lines from three tumour types were investigated and exposed to four classical anticancer drugs belonging to two classes characterized by a unique mechanism. First, each cell line was considered separately and a hierarchical clustering was built for the seven cell lines. Spectra clustered according to the drug mechanism of action for all the cell lines tested. Second, the similarities among drug mechanism spectral fingerprints were investigated for all the cell lines simultaneously. Difference spectra (the mean spectrum of the corresponding untreated cell line was subtracted) were computed so that the particular contribution of every cell line was eliminated and only the drug-induced differences could be compared. The hierarchical clustering shows a clear tendency to distinguish the two modes of action, revealing a very similar type of response to molecules with a similar mechanism. High throughput systems with 96-well plates are now available and a well established bioassay could be developed in order to provide an objective classifier for potential anticancer drugs.Journal ArticleResearch Support, Non-U.S. Gov'tSCOPUS: ar.jinfo:eu-repo/semantics/publishe

FTIR spectroscopy: a new valuable tool to classify the effects of polyphenolic compounds on cancer cells.

Polyphenolic compounds are an important part of human diet and regular consumption of fruits, vegetables and tea is associated with reduced risk of cancer. Dietary polyphenols display a vast array of cellular effects but the large number of data published in the literature makes it difficult to determine the main mechanisms of action associated and to identify molecules with original mechanisms. Therefore, there is an increasing demand for more systemic approaches in order to obtain a global insight of the biochemical processes mediated by polyphenols. Here, we used Fourier transform infrared (FTIR) spectroscopy to analyze cancer cells exposed in vitro to 6 polyphenols: 3 natural well documented polyphenols (curcumin, epigallocatechin gallate (EGCG) and quercetin) and 3 synthetic molecules with a very closely related chemical structure. Statistical analyses on FTIR spectra allowed the comparison of global effects of the 6 compounds and evidenced some common or different features in the cell perturbations among natural and synthetic molecules. Interestingly, marked metabolic changes induced by polyphenols closely related from a chemical point of view were identified. Furthermore, many metabolic changes could be detected as early as after 2h incubation with the drugs.Evaluation StudiesJournal ArticleResearch Support, Non-U.S. Gov'tSCOPUS: ar.jinfo:eu-repo/semantics/publishe