Nutrient-dependent sex determination

Gradual Molecular Evolution of a Sex Determination Switch through Incomplete Penetrance of Femaleness

Abstract excerpt: “We found that at least five amino acid differences and length variation between Csd specificities in the specifying domain (PSD) were sufficient to regularly induce femaleness.”

Highlights excerpt: “Amino acid polymorphisms in the specifying domain (PSD) determine femaleness”

Background: Sensory response system of social behavior tied to female reproductive traits

“…in wild-type honey bees, ovary size and vitellogenin mRNA level covary with the sucrose sensory response system, an important component of foraging behavior. This finding validates links between reproductive physiology and behavioral-trait associations of the pollen-hoarding syndrome of honey bees, and supports the forager-RGPH. Our data address a current evolutionary debate, and represent the first direct demonstration of the links between reproductive anatomy, physiology, and behavioral response systems that are central to the control of complex social behavior in insects.”

My comment: Sex differences in foraging behavior appear to be determined by nutrient-dependent amino acid substitutions in wild-type honeybees. This links their sex differences in morphology and behavior to nutrient-dependent pheromone-controlled sexual differentiation in unicellular yeasts via sex differences in nutrient uptake in the yeasts. In yeasts, the sex differences are linked to differences in glucose uptake and copy number variants via associations with olfactory receptor proteins: “One of the main duplicated gene families are the olfactory receptor proteins [18,117–119] so perhaps their duplication may lead to an increase in sensitivity to a particular odour may be adaptive under certain conditions.”

No experimental evidence suggests that sex differences in any species arise from what is typically referred to as mutation-initiated natural selection or mutation-driven evolution. No conserved molecular mechanisms indicate that sexual selection would result from natural selection for mutations.  All experimental evidence of conserved molecular mechanisms suggests that sex differences in copy number variation and amino acid polymorphisms result from nutrient-dependent alternative splicings that link the epigenetic landscape to the physical landscape of DNA in the organized genomes of species from microbes to man.  See for example: Signaling Crosstalk: Integrating Nutrient Availability and Sex and Feedback loops link odor and pheromone signaling with reproduction.

In our 1996 review article we (TB) wrote:

“Small intranuclear proteins also participate in generating alternative splicing techniques of pre-mRNA and, by this mechanism, contribute to sexual differentiation in at least two species, Drosophila melanogaster and Caenorhabditis elegans… ”

We (TB) added:

“Parenthetically it is interesting to note even the yeast Saccharomyces cerevisiae has a gene-based equivalent of sexual orientation (i.e., a-factor and alpha-factor physiologies). These differences arise from different epigenetic modifications of an otherwise identical MAT locus.”

Elekonich and Robinson (2000) integrated the model of hormone-organized and hormone-activated behavior that we helped to detail in the context of molecular epigenetics, and extended it to invertebrates. They wrote:

“The classical concepts, organization and activation, now seen as poles along a continuum of hormonal effects on behavior, provide a comprehensive framework for thinking about the effects of hormones on behavior. While the insect literature contains numerous examples  of hormone activation, explicit use of the organization concept provides a window into the developmental origins of phenotypic variation in behavior. It also broadens the time course over which hormonal actions on insect behavior are considered, from egg to adult.”

During the past decade, it has become clearer that nutrient-dependent pheromone-controlled alternative splicings and amino acid substitutions cause individual differences, species differences, and sex differences in the behavior of species that sexually reproduce across the lifetime. These differences represent the plasticity required to respond to the sensory environment with behaviors that are typically best for survival. Individuals and groups forage for food. Survival of species is nutrient-dependent and controlled by the metabolism of nutrients to species-specific pheromones that control the physiology of reproduction.

Author: James Kohl

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