Lecture 11 - environment nad symbiotic regulation of development

Metamorphosis

developmental changes that turn an immature organism into a new sexually mature form, controlled by hormones

What is the overarching goal of metamorphosis

To adapt to a new environment and lifestyle

Phenotypic plasticity

Ability of an organism to alters its form, state, movement, or activity rate in response to environmental inputs

Two types of developmental plasticity

Reaction norms, polyphenism

Reaction norms

Genome-environment interactive, results in MOST ADAPTIVE phenotype from a continuous range of phenotypes

Polyphenism

Discontinuous (either or) phenotypes induced by the environment

Diet polyphenism examples

1. Queen vs. worker bees: fed different foods (royal jelly, lipid/protein rich), queens get royalactin which triggers queen specific genes increasing yolk proteins

2. Queen vs. sterile male ants: only difference in development is diet

3. Spring caterpillars vs. summer caterpillars: same development but differ in oak leaf stage when consumed resulting in two different phenotypes

Dung beetle horns, polyphenism or reaction norm?

Have same genomes but get different lengths of horns that establish a dominance hierarchy, the presence or absence or absence of horns determine reproductive strategy. Because horns grow along a continuum it is a reaction norm

Mouse agouti gene

The agouti gene in mice determines fur color (presence = yellow) and reduces their lipid metabolism (store more fat), when the genes promoter is methylated transcription cannot occur. This is polyphenism, either yellow and fat, or dark and sleek

Predator polyphenism

Tadpole embryos can detect the vibrations of predator presence, when detected the tadpole chooses to hatch prematurely from egg and into the pond attempting to get away, if no predator is detected it hatches normally

Temperature as a developmental agent

TF distalless determines eye spot side in butterfly wings, it is regulated by both hormones and temperatures. Higher temperatures more 20E hormone = bigger and more eye spots. Continuum = reaction norm

Symbiosis

any close association between organisms of different species, host and symbiont

Parasitism

One benefits the other is harmed

Mutualism

Both benefit

Commensalism

One benefits, no effect on the other

Holobiont

the combination of the host and its symbionts

Vertical transmission

Transfer of symbionts from one generation to the next, commonly through eggs or other maternal forms of transmission

Horizontal transmission

host born free of symbionts, infected through environment or others

Are humans holobionts?

Yes, there are many microscopic organisms on our skin, in our gut, and all throughout our body that help us function and our bodies provide a safe space for them. 50% of our cells are other microorganisms

Gut bacteria of zebrafish and mice

bacteria regulate normal proliferation of intestinal stem cells, help with nutrient absorption, form blood vessels, fortifies ECM lining the intestine, also help upregulation intestinal gene transcription in mice, necessary for capillary and pancreas development with the help of the Befa protein made by the bacteria through insulin-secreting beta cells

Gut microbes and pregnant mice

gut bacteria in mouse blood makes its way through placenta into fetus, short chain fatty acid metabolites aid in activating metabolism genes important in mice, and help with the maturation of fetal brain neurons in the auditory region

Bacteria and the brain

Mammalian brain relies on Egr1 for neuronal plasticity, in mice the expression of this gene is dependent on symbiotic microbes

Gut microbiome in human pregnancy

Female gut microbiome changes during pregnancy, such as weight gain and insensitivity to insulin