Editorial: Glycans: molecules at the interface of immunity and disease

© 2024 The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/Peer reviewe

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

IMPLICATIONS OF THE COPERNICAN PRINCIPLE FOR MY MASTERS THESIS

Making only the assumption that you are an intelligent observer, an answer to the question: “So when will you be done your thesis anyway? ” can be derived at the 95 % confidence level. Estimates for the duration of my thesis (17.4 days to 72.7 years) agree, within an order of magnitude, with my life expectancy

Environment-specific heterozygote deficiency and developmental instability in hybrid Mytilus

The multiple discrete hybrid zones that characterize Mytilus blue mussels allow a novel, non-manipulative, examination of the selective pressures that create and maintain species. If endogenous genetic incompatibility is solely responsible for postzygotic isolation, then individuals of a specified hybrid genotype are expected to show similar average fitness across environments. However, if hybrid fitness differs across environments, then exogenous selection is implicated, either via ecological selection or environment-specific expression of intrinsic genetic incompatibilities. Correspondence between developmental instability of hybrids and heterozygote deficiency, estimated in two M. trossulus x M. galloprovincialis hybrid zones on the coast of North America, indicates that environment-dependent selection against hybrids may contribute to reproductive isolation among Pacific Mytilus species

Duplicate Abalone Egg Coat Proteins Bind Sperm Lysin Similarly, but Evolve Oppositely, Consistent with Molecular Mimicry at Fertilization

Sperm and egg proteins constitute a remarkable paradigm in evolutionary biology: despite their fundamental role in mediating fertilization (suggesting stasis), some of these molecules are among the most rapidly evolving ones known, and their divergence can lead to reproductive isolation. Because of strong selection to maintain function among interbreeding individuals, interacting fertilization proteins should also exhibit a strong signal of correlated divergence among closely related species. We use evidence of such molecular co-evolution to target biochemical studies of fertilization in North Pacific abalone (Haliotis spp.), a model system of reproductive protein evolution. We test the evolutionary rates (dN/dS) of abalone sperm lysin and two duplicated egg coat proteins (VERL and VEZP14), and find a signal of co-evolution specific to ZP-N, a putative sperm binding motif previously identified by homology modeling. Positively selected residues in VERL and VEZP14 occur on the same face of the structural model, suggesting a common mode of interaction with sperm lysin. We test this computational prediction biochemically, confirming that the ZP-N motif is sufficient to bind lysin and that the affinities of VERL and VEZP14 are comparable. However, we also find that on phylogenetic lineages where lysin and VERL evolve rapidly, VEZP14 evolves slowly, and vice versa. We describe a model of sexual conflict that can recreate this pattern of anticorrelated evolution by assuming that VEZP14 acts as a VERL mimic, reducing the intensity of sexual conflict and slowin

Positively selected residues occupy the exposed surface of egg coat proteins.

<p>Positively selected sites of the (A) VERL and (B) VEZP14 ZP-N motifs were inferred among 8 North Pacific abalone taxa using the Bayes Empirical Bayes (BEB) procedure of codeml <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003287#pgen.1003287-Yang3" target="_blank">[49]</a>, and sites with high posterior probabilities (>95%) were mapped to the respective structural models <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003287#pgen.1003287-Swanson3" target="_blank">[22]</a> using PyMol <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003287#pgen.1003287-Schrodinger1" target="_blank">[52]</a>. The positions of positively selected sites are given with reference to the complete coding sequences of VEZP14 and VERL (repeat 1 only) from red abalone (<a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003287#pgen.1003287-Aagaard1" target="_blank">[19]</a> and <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003287#pgen.1003287-Galindo1" target="_blank">[15]</a>, respectively). For VERL, the single site under positive selection identified with high posterior probability (V42) was inferred from the first two full VERL repeats, as statistical power from concatenated ZP-N motifs alone is insufficient to allow for predicting sites under selection via BEB (<a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003287#pgen-1003287-t001" target="_blank">Table 1</a>). This site occupies the same position of the structural model for ZP-N from VEZP14 (S171), with the majority of the remaining seven residues predicted to be under positive selection (N173, R187, E209, I218, L220, K228, and A233) occuring on the same exposed surface opposite the E′ extension (grey fill) thought to facilitate antiparallel pairing among intermolecular ZP-N motifs <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003287#pgen.1003287-Monne1" target="_blank">[23]</a>.</p

ZP-N from VERL and VEZP14 bind lysin with comparable affinity.

<p>The ZP-N motif from VEZP14 and the first repeat of green abalone VERL were cloned, expressed in <i>Drosophila</i> S2 cells (Invitrogen, Carlsbad, CA), and affinity purified (<a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003287#pgen.1003287.s002" target="_blank">Figure S2</a>). (A) An in-house surface plasmon resonance (SPR) detection system <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1003287#pgen.1003287-Chinowsky1" target="_blank">[54]</a> was used to estimate binding of green abalone sperm lysin to surfaces coated with VERL (dark green) or VEZP14 (light green) as measured by refractive index (two replicates each). Numbered shoulders of the SPR curves indicate the intervals used to calculate the association (k_a, 1–2) and dissociation (k_d,2–3) rates via Scrubber2 (Center for Biomolecular Interaction Analysis, University of Utah). (B) Mean dissociation constants calculated from SPR data (K_D = k_d/k_a) show lysin has slightly higher, though comparable, affinity for the ZP-N motif from VERL (520 nM) and VEZP14 (580 nM; lower K_D values indicate higher affinity), demonstrating the ZP-N motif of egg coat proteins alone is sufficient to bind sperm lysin.</p