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PubMed2002

Cell surface polarization during yeast mating.

Exposure to mating pheromone in haploid Saccharomyces cerevisiae cells results in the arrest of the cell cycle, expression of mating-specific genes, and polarized growth toward the mating partner. Proteins involved in signaling, polarization, cell adhesion, and fusion are localized to the tip of the mating cell (shmoo) where fusion will eventually occur. The mechanisms ensuring the correct targeting and retention of these proteins are poorly understood. Here we show that in pheromone-treated cells, a reorganization of the plasma membrane involving lipid rafts results in the retention of proteins at the tip of the mating projection, segregated from the rest of the membrane. Sphingolipid and ergosterol biosynthetic mutants fail to polarize proteins to the tip of the shmoo and are deficient in mating. Our results show that membrane microdomain clustering at the mating projection is involved in the generation and maintenance of polarity during mating.

Acyltransferases↗

PubMed1998

The role of Cdc42 in signal transduction and mating of the budding yeast Saccharomyces cerevisiae.

The small G-protein Cdc42 functions in many eukaryotic signal transduction pathways. In the budding yeast Saccharomyces cerevisiae, cells with defective Cdc42 fail to induce mating-specific genes in response to mating factor and to adopt the proper morphology for conjugation. Here we show that the failure of mating factor-induced transcription is largely the indirect result of arrest at a specific cell cycle position and/or the accumulation of high levels of the Cln1/2-Cdc28 kinase, a known repressor of mating factor signal transduction. Cdc42-defective cells with restored transcriptional induction have a partially restored mating ability but are still defective in the morphological response to mating factor. These results show that Cdc42 is not required for transduction of the mating factor signal per se but that it is essential for proper mating factor-induced morphogenesis.

CDC28 Protein Kinase, S cerevisiae↗

PubMed1991

Role of alpha-factor and the MF alpha 1 alpha-factor precursor in mating in yeast.

The peptide pheromones secreted by a and alpha cells (called a-factor and alpha-factor, respectively) are each encoded by two structural genes. For strains of either mating type, addition of exogenous pheromone does not alleviate the mating defect of mutants with disruptions of both structural genes. In addition, a particular insertion mutation in the major alpha-factor structural gene (MF alpha 1) that should result in an altered product inhibits alpha mating. These results suggested that the pheromone precursors (the MF alpha 1 pro region in particular) might play a second role in mating separate from the role of pheromone production. To analyze the role of alpha-factor and the MF alpha 1 precursor in alpha mating, we have constructed two classes of mutants. The mating defects of mutants that should produce the MF alpha 1 pro region peptide but no alpha-factor could not be alleviated by addition of exogenous alpha-factor in crosses to a wild-type a strain, indicating that the previous results were not due to an inability of the disruption mutants to produce the pro region peptide. Mutants able to produce alpha-factor, but with a variety of alterations in MF alpha 1 precursor structure, mated at levels proportional to the levels of alpha-factor produced, suggesting that the only role of the alpha-factor precursor in mating is to produce alpha-factor. Both of these results argue against a role for the MF alpha 1 pro region separate from its role in alpha-factor production.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed1994

Directed replacement of mt A by mt a-1 effects a mating type switch in Neurospora crassa.

To test the functions of a mating type genes, we developed an efficient strategy to select transformants of Neurospora crassa in which resident A mating type DNA was replaced by cloned DNA from the mt a idiomorph. Cloned a idiomorphic DNA could specify all functions, including fertility, of a mating type, but only when it replaced A DNA at the mating type locus. Only the mt a-1 region of the a idiomorph was necessary in order to specify a mating type. Gene replacement events involved the homologous sequences flanking the unique mating type idiomorphic DNA, resulting in apparently isogenic a and A strains. These isogenic strains were fertile when crossed with one another, indicating that no determinants outside the transforming DNA are necessary for fertility as a and that no host sequences of A strains interfere with fertility as a. One a replacement strain bore a duplication of the transforming mt a-1 and hph DNA. The duplication strain had unexpected properties. Although mating type segregated 1:1 in crosses of this strain to A, the duplicated regions were efficiently altered during the sexual process to generate a single copy in the progeny. No progeny were recovered that had undergone RIP (repeat induced point mutation) sufficient to inactivate the mt a-1 gene. We infer that the mt a-1 gene is necessary and sufficient to specify a mating type identity in all vegetative and sexual activities. Mt a-1 may also play an essential role in ascosporogenesis after fertilization.

Cloning, Molecular↗

PubMed1996

Genetic and physical variability at the mating type locus of the oomycete, Phytophthora infestans.

Mating type in the oomyceteous fungus, Phytophthora infestans, is determined by a single locus. In a previous study of a few isolates, the locus segregated in a manner genetically consistent with its linkage to a system of balanced lethal loci. To determine the prevalence of this phenomenon within P. infestans, genetic analyses were performed using isolates representative of the diversity within the species that had been selected by DNA fingerprinting using probes linked to mating type. Non-Mendelian segregation of the mating type locus was observed in crosses performed with each isolate. An unusual group of isolates was identified in which the mating type determinants had been rearranged within the genome; these strains also produced an aberrantly large number of self-fertile progeny. Curiously, in all isolates, markers linked to the mating type locus appeared prone to duplication, transposition, deletion, or other rearrangement. This was not observed for loci unlinked to mating type. Data from the crosses and analyses of marker variation were used to erect models to explain the bases of mating type determination and of the unusual segregation of the chromosomal region containing the mating type locus.

DNA Fingerprinting↗

PubMed1999

Molecular characterization of tol, a mediator of mating-type-associated vegetative incompatibility in Neurospora crassa.

The mating-type locus in the haploid filamentous fungus, Neurospora crassa, controls mating and sexual development. The fusion of reproductive structures of opposite mating type, A and a, is required to initiate sexual reproduction. However, the fusion of hyphae of opposite mating type during vegetative growth results in growth inhibition and cell death, a process that is mediated by the tol locus. Mutations in tol are recessive and suppress mating-type-associated heterokaryon incompatibility. In this study, we describe the cloning and characterization of tol. The tol gene encodes a putative 1011-amino-acid polypeptide with a coiled-coil domain and a leucine-rich repeat. Both regions are required for tol activity. Repeat-induced point mutations in tol result in mutants that are wild type during vegetative growth and sexual reproduction, but that allow opposite mating-type individuals to form a vigorous heterokaryon. Transcript analyses show that tol mRNA is present during vegetative growth but absent during a cross. These data suggest that tol transcription is repressed to allow the coexistence of opposite mating-type nuclei during the sexual reproductive phase. tol is expressed in a mat A, mat a, A/a partial diploid and in a mating-type deletion strain, indicating that MAT A-1 and MAT a-1 are not absolutely required for transcription or repression of tol. These data suggest that TOL may rather interact with MAT A-1 and/or MAT a-1 (or downstream products) to form a death-triggering complex.

Amino Acid Sequence↗

PubMed2025

Major histocompatibility complex class IIB disassortative mate choice in a genetically monogamous seabird.

Among species reproducing sexually, mating strategies represent a major component of individual fitness. The major histocompatibility complex (MHC) is an extremely diverse set of genes responsible for immunological recognition and defence against pathogens. Although dissimilarity between mates at the major histocompatibility complex has been proposed to drive mate choice through increased offspring pathogen resistance, evidence is mixed. In addition, explorations of the role of the major histocompatibility complex in other mating strategies, such as divorce, are rare. We investigated whether dissimilarity at the major histocompatibility complex class IIB is associated with mate choice and divorce probability in the genetically monogamous black-legged kittiwake (Rissa tridactyla). We found that first-time male breeders, as well as divorced males, were paired with females more dissimilar at the major histocompatibility complex class IIB than expected under random mating. We did not find evidence for mate choice based on major histocompatibility complex class IIB dissimilarity when considering females. In addition, in the studied population, divorce probability was very low compared with other populations and did not significantly vary with the dissimilarity of the pair at the major histocompatibility complex class IIB. Our results pave the way to a better understanding of the complex role of major histocompatibility complex dissimilarity in mating decisions of species displaying mutual choice and biparental care.

Animals↗

PubMed1988

The a-factor pheromone of Saccharomyces cerevisiae is essential for mating.

The Saccharomyces cerevisiae pheromone a-factor is produced by a cells and interacts with alpha cells to cause cell cycle arrest and other physiological responses associated with mating. Two a-factor structural genes, MFA1 and MFA2, have been previously cloned with synthetic probes based on the a-factor amino acid sequence (A. Brake, C. Brenner, R. Najarian, P. Laybourn, and J. Merryweather, cited in M.-J. Gething [ed.], Protein transport and secretion, 1985). We have examined the function of these genes in a-factor production and mating by construction and analysis of chromosomal null mutations. mfa1 and mfa2 single mutants each exhibited approximately half the wild-type level of a-factor activity and were proficient in mating, whereas the mfa1 mfa2 double mutant produced no a-factor and was unable to mate. These results demonstrate that both genes are functional, that each gene makes an equivalent contribution to the a-factor activity and mating capacity of a cells, and that a-factor plays an essential role in mating. Strikingly, exogenous a-factor did not alleviate the mating defect of the double mutant, suggesting that an a cell must be producing a-factor to be an effective mating partner.

Amino Acid Sequence↗

PubMed2005

Evidence for mitochondrial gene control of mating types in Phytophthora.

When protoplasts carrying metalaxyl-resistant (Mr) nuclei from the A1 isolate of Phytophthora parasitica were fused with protoplasts carrying chloroneb-resistant (Cnr) nuclei from the A2 isolate of the same species, fusion products carrying Mr nuclei were either the A2 or A1A2 type, while those carrying Cnr nuclei were the A1, A2, or A1A2 type. Fusion products carrying Mr and Cnr nuclei also behaved as the A1, A2, or A1A2 type. The result refutes the hypothesis that mating types in Phytophthora are controlled by nuclear genes. When nuclei from the A1 isolate of P. parasitica were fused with protoplasts from the A2 isolate of the same species and vice versa, all of the nuclear hybrids expressed the mating type characteristics of the protoplast parent. The same was true when the nuclei from the A1 isolate of P. parasitica were fused with the protoplasts from the A0 isolate of Phytophthora capsici and vice versa. These results confirm the observation that mating type genes are not located in the nuclei and suggest the presence of mating type genes in the cytoplasms of the recipient protoplasts. When mitochondria from the A1 isolate of P. parasitica were fused with protoplasts from the A2 isolate of the same species, the mating type of three out of five regenerated protoplasts was changed to the A1 type. The result demonstrated the decisive effect of mitochondrial donor sexuality on mating type characteristics of mitochondrial hybrids and suggested the presence of mating type genes in mitochondria. All of the mitochondrial hybrids resulting from the transfer of mitochondria from the A0 isolate of P. capsici into protoplasts from the A1 isolate of P. parasitica were all of the A0 type. The result supports the hypothesis of the presence of mating type genes in mitochondria in Phytophthora.

Alanine↗

PubMed2026

REVIEW: CAUSES AND CONSEQUENCES OF DOING IT WITH ONESELF-SYNTHESIS AND META-ANALYSIS OF NEODERMATAN HERMAPHRODITIC MATING SYSTEMS.

Hermaphroditic mating systems profoundly influence evolution, yet in parasitic flatworms (Neodermata) they remain strikingly understudied. For decades, sweeping claims have oscillated between pervasive selfing and near-universal outcrossing, reflecting a lack of comprehensive synthesis. This review, the first in more than 40 yr, integrates nearly a century of research, from early observational studies to modern genetic analyses, to reveal a far more nuanced picture. Our meta-analysis of population-genetic data shows a sharp departure from the bimodal selfing patterns typical of plants and other hermaphroditic animals: neodermatan parasites are strongly skewed toward outcrossing. We link variation in mating systems to parasite demography and life-history traits, especially in species exhibiting mixed mating or elevated selfing. Current evidence suggests outcrossing is common, but taxonomic and life-history gaps preclude definitive conclusions. Beyond patterns and causes, we explore evolutionary consequences ranging from fitness costs such as inbreeding depression to trait evolution, including delayed selfing, sex allocation, and complex life cycles. Evidence for inbreeding depression is mixed and limited, yet emerging approaches using selfing-rate comparisons offer promising avenues for future research. Notably, demographic constraints, such as infection intensity and life-cycle architecture, often explain mixed mating without invoking selection, challenging classical models. Similarly limited in number, studies on sex allocation indicate that hermaphroditic mating systems can shape reproductive investment, with patterns consistent with local sperm competition in some taxa. By consolidating historical observations with modern genetic insights, this review provides the most comprehensive synthesis of hermaphroditic mating systems in the Neodermata to date. We highlight critical gaps in taxonomic coverage and experimental data and point to future opportunities for integrating genomic approaches with ecological and demographic frameworks. Such integration will be essential to illuminate how mating systems shape parasite evolution and to resolve long-standing questions about the persistence of mixed mating despite theoretical expectations.

Animals↗

PubMed2006

The evolution of female mating preferences: differentiation from species with promiscuous males can promote speciation.

Females of many species are frequently courted by promiscuous males of their own and other closely related species. Such mating interactions may impose strong selection on female mating preferences to favor trait values in conspecific males that allow females to discriminate them from their heterospecific rivals. We explore the consequences of such selection in models of the evolution of female mating preferences when females must interact with heterospecific males from which they are completely postreproductively isolated. Specifically, we allow the values of both the most preferred male trait and the tolerance of females for males that deviate from this most preferred trait to evolve. Also, we consider situations in which females base their mating decisions on multiple male traits and must interact with males of multiple species. Females will rapidly differentiate in preference when they sometimes mistake heterospecific males for suitable mates, and the differentiation of female preference will select for conspecific male traits to differentiate as well. In most circumstances, this differentiation continues indefinitely, but slows substantially once females are differentiated enough to make mistakes rare. Populations of females with broader preference functions (i.e., broader tolerance for males with trait values that deviate from females' most preferred values) will evolve further to differentiate if the shape of the function cannot evolve. Also, the magnitude of separation that evolves is larger and achieved faster when conspecific males have lower relative abundance. The direction of differentiation is also very sensitive to initial conditions if females base their mate choices on multiple male traits. We discuss how these selection pressures on female mate choice may lead to speciation by generating differentiation among populations of a progenitor species that experiences different assemblages of heterospecifics. Opportunities for differentiation increase as the number of traits involved in mate choice increase and as the number of species involved increases. We suggest that this mode of speciation may have been particularly prevalent in response to the cycles of climatic change throughout the Quaternary that forced the assembly and disassembly of entire communities on a continentwide basis.

Animals↗

PubMed1996

Reproduction in free-ranging Propithecus verreauxi: estrus and the relationship between multiple partner matings and fertilization.

Female sifaka mate selectively with one or more resident and/or non-resident males during the breeding season. Various adaptive explanations have been advanced to explain why female primates mate with multiple males including that 1) females seek to confuse paternity and thereby forestall male infanticide and/or ensure male infant care or 2) females seek to ensure fertilization. Assessing the power of fertilization insurance to explain mating patterns in females requires information on the temporal relationship between mating and ovarian hormones. The hormonal correlates of reproduction and mating in free-ranging Propithecus verreauxi were investigated using excreted steroids as indices of reproductive state. Solid-phase extraction and radioimmunoassay techniques were used to measure unconjugated estradiol (E(2)) and progesterone (P(4)) in 485 desiccated fecal samples collected from five female sifaka before and during the breeding season at Beza Mahafaly, Madagascar. Results suggest that behavioral estrus was characterized by 10 to 15-day elevations in E(2); hormonal activity was observed to be similar to pseudo-estrus reported for other lemur species; apparent conception was associated with sustained P4 elevations beginning 1 to 3 days post-estrus with gestational phase elevations of E2 beginning 42 to 45 days post-conception; and mating with multiple partners appeared not to be a prerequisite to fertilization, as conception resulted from both monoandrous and polyandrous matings. These preliminary data suggest that fertilization insurance is not adequate to explain polyandrous mating in sifaka at Beza Mahafaly.

Animals↗

PubMed2000

Seasonality of matings and births in captive Sichuan golden monkeys (Rhinopithecus roxellana).

This study, based on three years of mating behavior observations and 10 years of birth records, reveals that Sichuan golden monkeys in captivity displayed a marked seasonality of mating behavior and births. The peak of matings occurred around October, and births occurred in March-June. The birth peak followed the mating peak by six to seven months. This seasonal cycle of matings and births was similar to observations made in the wild, where both temperature and food resources were favorable in spring. The time delay between peaks of matings and births was the approximate length of gestation, which implies that mating behavior was concentrated during the period of conception. We suggest that the peak of births in captive Sichuan golden monkeys occurred during the time of year with the most favorable environmental conditions, and the peak of matings corresponded with the period of conception.

Animals↗

PubMed1992

Growth and differentiation schedule of mouse embryos obtained from delayed matings.

We previously showed that digit formation in mouse embryos from early morning mating seemed to progress faster than those from overnight mating. In this study, to confirm this phenomenon, we examine whether the embryos from normal (0 hr from ovulation to fertilization) and delayed matings (3, 6, or 9 hr from ovulation to fertilization) respond differently to some acute teratogens when they are treated at the same time point from mating. Five mg/kg of cytosine arabinoside (Ara-C) was given to pregnant mice intraperitoneally at 246, 249, or 252 hr (day of gestation (dg) 10) after mating. The patterns of Ara-C induced digit malformations in embryos from the delayed mating groups were those of more advanced stages, when compared with normal mating groups with the same time intervals from mating to Ara-C treatment. In other words, oocytes fertilized up to 9 hr after the presumed time of ovulation could grow similarly to those of normally fertilized oocytes. This catch-up phenomenon suggests that the ovulation clock should be used for the startpoint of the time scale of the growth and differentiation of embryos rather than fertilization clock.

Animals↗

PubMed1997

Reproductive synchrony and extra-pair mating strategy in a socially monogamous bird, Dendroica petechia

Depending on the circumstances under which extra-pair mating occurs, theory makes opposing predictions about how reproductive synchrony should influence extra-pair paternity. This study investigated which sex initiated extra-pair mating in the yellow warbler, whether extra-pair behaviour and extra-pair paternity were related to reproductive synchrony, and whether synchrony affected the mating success of all males equally. Observations and captures of individuals making territorial intrusions indicated that males initiated extra-pair mating. Spatial patterns of male territorial intrusions and of extra-pair paternity were similar. Males' extra-pair activity was reduced when their social partner was fertile. More offspring were sired by the extra-pair male when the female nested asynchronously with that sire's social mate. Neither population-wide synchrony, nor synchrony with neighbours, however, seemed to predict the incidence of extra-pair parentage or the identity of the sire, indicating factors other than synchrony were also important. Males with more breast streaking (a plumage ornament) were more successful as extra-pair sires, and were least affected by the constraint of synchrony. Larger males were less often cuckolded, and achieved extra-pair success mainly when their partner was not fertile. Thus, male yellow warblers apparently use different mating tactics depending on their plumage and size. More generally, the results suggest how mating strategies are affected by which sex initiates extra-pair mating and by the relative contributions of within-pair and extra-pair paternity to total reproductive success.Copyright 1997 The Association for the Study of Animal BehaviourCopyright 1997The Association for the Study of Animal Behaviour.

Journal Article↗

PubMed1999

Cultural influences on female mate choice: an experimental test in cowbirds, Molothrus ater.

Previous studies of brown-headed cowbirds Molothrus ater, have shown that social learning and cultural transmission can influence courtship and mating patterns. These earlier studies did not test whether cultural background influenced mate choice in females and therefore whether culture could potentially play a role in sexual selection in this species, as has been suggested by recent theory. Here, we tested whether culture influences female mate choice in brown-headed cowbirds. Female cowbirds from a South Dakota population were housed with adult cowbirds from the same South Dakota population or with adult cowbirds from a behaviourally distinct population from Indiana. We tested the mating preferences of females of the South Dakota culture and females of the Indiana culture in sequential mate-choice trials with males, controlling for intrasexual interactions. The males were South Dakota cowbirds that had also been housed either in the South Dakota culture or in the Indiana culture. Females showed mating preferences for males from their own culture. These results suggest that mate choice in female cowbirds can be influenced by cultural background. We briefly discuss the effect that culture may have on sexual selection and on the evolution of female mating preferences. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗

PubMed1999

Mate choice copying versus preference for actively displaying males by female pied flycatchers.

Should a female copy the mate choice of other females? A female may rank a mated male higher in quality than an unmated male because the former has demonstrated that he is able to attract a female. However, a prospecting female may also avoid a mated male because of the risk that she has to compete with the male's initial mate over access to copulations, breeding resources and male parental care. We studied the mate choice of female pied flycatchers Ficedula hypoleuca, in aviaries divided into three compartments, two for males, and one for a female. A female was allowed to choose (build a nest in a nestbox) between two males after a period when she had been kept in a cage behind a one-way mirror and had presumably seen that one of the males was in the company of another female for 5 h. There was no evidence that females copied the mate choice of conspecific females, or that they avoided males that had recently been in the company of another female. Instead, females apparently chose a mate independently of others, choosing the male showing most courtship display. The latter result explains the consistency in mate choice observed when different females chose between the same pair of males in repeat trials. The ability of females to pick out the same male independently may also explain why a few males obtain most copulations in lekking species. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗

PubMed2000

Components of lifetime mating success and body size in males of a scrambling damselfly.

Sexual selection is hypothesized to favour small body size in males of scrambling species, that is, those in which males obtain matings by actively searching for females. I tested this hypothesis in a natural population of the scrambling emerald damselfly, Lestes sponsa. Mating efficiency (matings/visit to the pond) was the most important factor explaining variation in male lifetime mating success (LMS; 71%). This suggests a large potential for sexual selection. Path analysis of male LMS suggested a quality factor that positively affected both mating efficiency and life span. In contrast with the small-male mating advantage hypothesis, part of this potential for sexual selection was realized as stabilizing selection on male body size, indicating that there may also be a lower limit to body size for mating efficiency. This also illustrates that the constancy of body size may be explained by sexual selection alone. Survival explained about 20% of the variation in LMS and random processes were potentially important for determining LMS. My results show the problems of using mating efficiency as a measure for the intensity of sexual selection and the need to distinguish between potential and realized selection pressures, especially when comparing the importance of natural and sexual selection. I discuss mechanisms that may have caused the intermediate-male mating advantage in this scrambling species. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗