l21 ecological development

Classic view of genetics vs modern

classical

genotype —> phenotype

modern=developmental plasticity

The ability for a single genotype to give rise to alternative (different) phenotypes due to environmental variation acting on developmental processes.

genotype + env — > phenotype

Biotic and Abiotic environmental factors

The “Triple Helix”

two genotypes (A & B), 2 environments (1 & 2)

• each genotype can interact with each environment

• as a result, there are 12 possible resulting phenotypes

Epigenetic landscape

represents developmental trajectories

• the ball falls down the landscape and can go down different directions

• waddington called this the epigenetic landscape

• the direction it goes can lead to different cell or organism outcomes

• direction can be influenced by environmental variation

• he also few wires under to represent gene networks that can influence the shape of the landscape (gene variation also matters!)

Caste Plasticity in Bee

• diet/nutrition in larvae impact the landscape, causing queen vs worker bee

  • royal jelly —> queen

  • worker food —> worker

• also causes different epigenetic and hormonal response —> causes the different castes

Royal jelly is what + impact

contains Juvenile Hormone Royalactin

• upregulates reproductive organ development

• causes queen bee

worker jelly is what + impact

contain miR162a Queen Mandibular Pheromone

• bind to 3’ UTR of genes, causing their suppression

• this miRNA is in pollen

• causes worker bee

How does miR162a bind to TOR ** verify this

• able to bind to animal transcript’s TOR

Seasonal wing plasticity in Bicyclus anyana butterflies: what are the two phenotypes

• based on the abiotic environmental factor: temperature

• (A) Wet season female - huge eyespots!

• (B) dry season female, incredible leaf/ground camouflage to help it wait until the wet season comes back.

Seasonal wing plasticity in Bicyclus anyana butterflies: how does this happen

• low temp: decreased amount of sterioid hormone 20—hydroxyecdysone

  • no eye spots

• high temp: increased amount of 20—hydroxyecdysone

  • distal-less gene expression —> patterns eye spots

Environmental Stress & Developmental plasticity of Metamorphosis in salamanders

• Biotic: Predator & Abiotic: Drought

• drought—> high thyroid hormone production =Metamorph

• low predators —> low thyroid hormone production = Paedomorph

Prey-induced plasticity

• New Mexico spadefoot toad

• carnivore (Eat other tapoles) vs omnivore

  • each have different phenotypes

Predator-induced plasticity

• able to detect predators using allelochemical/kairomones received from that predator; molecules signalled between individuals of different species

• predator has a hard time eating them

Developmental plasticity in ants

• all different shapes an sizes

• Environmental factors determine which caste a developing ant will become

• Same genome ---> different phenotypes

• queen vs worker: Abiotic (temp & photoperiod)

• Soldier vs worker: Biotic (Nutrition)

Caste differentiation in ants

• embryo

• high JH —> queen

• at different time of yr —> high JH=soldier, low=minor worker

  • in solider larvae: JH activates wing disc —> proliferates + causes large head —> tissue undergoes apoptosis

  • worker=small head

• negative feedback to control # of soldiers: if too many soldiers, they make an inhibitory hormone that stops formation into soldiers

DNA methylation

• epigenetics

• environmentally sensitive process

• can cause genes to be turned off in response to the environment

  • demethyltransferases reverse this

• Can be inherited from one generation to the nextS

epigenetics + ants

DNA methylation regulates worker ant size plasticity

• Worker size sensitive to nutrition (protein) levels

• Developmental DNA methylation levels can influence worker size variation

• Quantitative DNA methylation (different levels) of Epidermal Growth Factor Receptor (Egfr) regulates worker size variation

epigenetics in mice

DNA methylation regulates coat color plasticity in mice

• The murine agouti gene encodes a paracrine signaling molecule that signals follicular melanocytes to switch from producing black eumelanin to yellow phaeomelanin

• viable-yellow of Agouti- transposon (Avy ) in cis-regulatory element

  • DNA methylation silences Avy activity and gene expression -> depending on degree leads to different coat colours

• Dietary Folate impacts rate of dna methylation

  • folate is a key source of the methyl groups

Epigenetics in reptiles

Histone methylation regulates plasticity of sex

developmental plasticity in beetles + one example

Horn developmental plasticity in beetles: Presence/Absence of horn and everything in between

example: Onthophagus beetles (dung beetles)

• some males horned + others hornless. as body size increases, so does horn growth. this is driven by JH and influenced by nutrition

Evolution of Onthophagus beetle sexual dimorphism

4 Major parameters:

• Location of hormone

• Shape

• Allometry (proportional sizing of hormone to body size)

• Sexual dimorphism - diff between female and male

Genetic Sex Determination in Drosophila melanogaster

• level of dsx influences whether grow a horn or not

• Males and females have unique doublesex isoforms. Large males upregulate dsx compared to small males and females.

• Male doublesex RNAi reduces large horns of large males and induces ectopic horns in hornless females! Doublesex has opposing roles between males and females.

• loss of function of dsx:

  • small male (small diet) - not big effect

  • large male - form tiny horns

  • OPPOSITE in females.

    • large = suppresses horns in females

Diet-induced Jaw Plasticity in Cichlid Fish (oral jaw)

• species are competing for resources and adapt to other food sources to avoid overlapping food sources

• lake malawi, tanganyika, and more

Oral Jaw versus Pharyngeal Jaw

Pharyngeal Jaw; extra jaw inside mouse with its own set of teetch. can shoot out to eat something

present in Cichlid Fish