evo......... evo........devo evo - devo: evolution and development i. background
TRANSCRIPT
Evo........
Evo........Devo
Evo - Devo: Evolution and Development
I. Background
Evo - Devo
I. Background
- Embrologists have long realized that organisms in different phyla have different developmental "plans"
Evo - Devo
I. Background
- Embrologists have long realized that organisms in different phyla have different developmental "plans"
- And in a phylum, there is the same developmental plan. This is not necessarily what we might expect from random mutation and evolution... why don't we see as many differences in early developmental traits as we see in later developing traits?
- For instance, why do chordates have similar development, even though cartilaginous fish and other vertebrates are separated by 400 million years of divergent evolution?
Evo - Devo
I. Background
- Embrologists have long realized that organisms in different phyla have different developmental "plans"
- And in a phylum, there is the same developmental plan. This is not necessarily what we might expect from random mutation and evolution... why don't we see as many differences in early developmental traits as we see in later developing traits?
- For instance, why do chordates have similar development, even though cartilaginous fish and other vertebrates are separated by 400 million years of divergent evolution.
- Embryological development is highly conserved, while subsequently allowing extraordinary variation....
Evo - Devo
I. Background
II. Core Processes
- Basic biological processes are CONSERVED, and the enzymes that perform them are CONSERVED:
Evo - Devo
I. Background
II. Core Processes
- Basic biological processes are CONSERVED, and the enzymes that perform them are CONSERVED:
DNA, RNA, protein synthesis - ALL LIFE
Evo - Devo
I. Background
II. Core Processes
- Basic biological processes are CONSERVED, and the enzymes that perform them are CONSERVED:
DNA, RNA, protein synthesis - ALL LIFE
Membrane structure and function - ALL EUK's
Evo - Devo
I. Background
II. Core Processes
- Basic biological processes are CONSERVED, and the enzymes that perform them are CONSERVED:
DNA, RNA, protein synthesis - ALL LIFE
Membrane structure and function - ALL EUK's
Cell junctions - ALL METAZOA
Evo - Devo
I. Background
II. Core Processes
- Basic biological processes are CONSERVED, and the enzymes that perform them are CONSERVED:
DNA, RNA, protein synthesis - ALL LIFE
Membrane structure and function - ALL EUK's
Cell junctions - ALL METAZOA
Hox genes - ALL BILATERIA
Evo - Devo
I. Background
II. Core Processes
- Basic biological processes are CONSERVED, and the enzymes that perform them are CONSERVED:
DNA, RNA, protein synthesis - ALL LIFE
Membrane structure and function - ALL EUK's
Cell junctions - ALL METAZOA
Hox genes - ALL BILATERIA
Limb formation - ALL LAND VERTEBRATES
Evo - Devo
I. Background
II. Core Processes
- Basic biological processes are CONSERVED, and the enzymes that perform them are CONSERVED:
- Many enzymes are more than 50% similar in AA sequence in E. coli and H. sapiens, though separated by 2 billion years of divergence.
- Of 548 metabolic enzymes in E. coli, 50% are present in ALL LIFE, and only 13% are unique to bacteria.
Evo - Devo
I. Background
II. Core Processes
- Basic biological processes are CONSERVED, and the enzymes that perform them are CONSERVED:
- Many enzymes are more than 50% similar in AA sequence in E. coli and H. sapiens.
- Of 548 metabolic enzymes in E. coli, 50% are present in ALL LIFE, and only 13% are unique to bacteria.
- So the variation and diversity of life is NOT due to changes in metabolic or structural genes... we are all built out of the same stuff, that works the same way at a cellular level.
Evo - Devo
I. Background
II. Core Processes
- Basic biological processes are CONSERVED, and the enzymes that perform them are CONSERVED:
- Many enzymes are more than 50% similar in AA sequence in E. coli and H. sapiens.
- Of 548 metabolic enzymes in E. coli, 50% are present in ALL LIFE, and only 13% are unique to bacteria.
- So the variation and diversity of life is NOT due to changes in metabolic or structural genes... we are all built out of the same stuff, that works the same way at a cellular level.
- Variation is largely due to HOW these processes are REGULATED... 300 cell types in humans, all descended from the zygote; all genetically the same.
Evo - Devo
I. Background
II. Core Processes
III. Weak Linkage Regulation
- Development is NOT a single process
Evo - Devo
I. Background
II. Core Processes
III. Weak Linkage Regulation
- Development is NOT a single process
- Development is a well choreographed dance of many parallel processes...
Evo - Devo
I. Background
II. Core Processes
III. Weak Linkage Regulation
- Development is NOT a single process
- Development is a well choreographed dance of many parallel processes...
- How is the parallelism maintained, ESPECIALLY as one process evolves?
Evo - Devo
I. Background
II. Core Processes
III. Weak Linkage Regulation
- Development is NOT a single process
- Development is a well choreographed dance of many parallel processes...
- How is the parallelism maintained, ESPECIALLY as one process evolves?
- Because they may be triggered by the same (or subsets of the same) REGULATORS... these are transcription factors that can turn suites of metabolic/structural genes on and off.
Evo - Devo
I. Background
II. Core Processes
III. Weak Linkage Regulation
- Development is NOT a single process
- Development is a well choreographed dance of many parallel processes...
- How is the parallelism maintained, ESPECIALLY as one process evolves?
- Because they may be triggered by the same (or subsets of the same) REGULATORS... these are transcription factors that can turn suites of metabolic/structural genes on and off. And transcription factors can interact.
Evo - Devo
I. Background
II. Core Processes
III. Weak Linkage Regulation
- Best (and most fundamental) examples are HOX genes. These are 'homeotic genes' that produce a variety of transcription factors. The production and localization of these transcription factors are CRITICAL in determining the 'compartments' of bilaterally symmetrical animals.
Evo - Devo
I. Background
II. Core Processes
III. Weak Linkage Regulation
- Duplication of hox genes can lead to differential regulation in different segments, and different phenotypes in different segments.
inhibition of limb development
Evo - Devo
I. Background
II. Core Processes
III. Weak Linkage Regulation
- Duplication of hox genes can lead to differential regulation in different segments, and different phenotypes in different segments.
Each gene produces a DNA binding protein that turns on a set of genes... different hox genes produce different binding proteins, that stimulate different sets of genes...that are ALL regulated by THIS transcription factor (linked regulation - coordinated response).
Evo - Devo
I. Background
II. Core Processes
III. Weak Linkage Regulation
- Effects can be profound
antennaepedia
Evo - Devo
I. Background
II. Core Processes
III. Weak Linkage Regulation
- Effects can be profound
- But they demonstrate the 'modularity' of
the developmental plan - only single units
are affected.
Bithorax
Evo - Devo
I. Background
II. Core Processes
III. Weak Linkage Regulation
- Effects can be profound
- But they demonstrate the 'modularity' of
the developmental plan - only single units
are affected.
- 'Master Switches' that initiate downstream cascades that can be very different... like compound or vertebrate eyes.
Evo - Devo
I. Background
II. Core Processes
III. Weak Linkage Regulation
- and they are still integrated with the rest of the organism
For example, the length of a breed's snout correlated directly with the number of repeats in a gene called Runx-2. Runx-2's tandem repeat consists of two different three-base sequences, randomly ordered along the length of the repeat. If there's more of one threesome relative to the other, that breed's muzzle tends to be longer and straighter. Fonden and Garner. 2004. PNAS
Evo - Devo
I. Background
II. Core Processes
III. Weak Linkage Regulation
- Types of Regulation
Enhancer - upstream activation sequence. Binding site for transcription factor.
Mutation here is cis-regulation
(within the operational "cistron")
Evo - Devo
I. Background
II. Core Processes
III. Weak Linkage Regulation
- Types of Regulation
Enhancer - upstream activation sequence. Binding site for transcription factor.Mutation here is cis-regulation(within the operational "cistron")
mutation in the transcription factor gene is called trans-regulation
Evo - Devo
I. Background
II. Core Processes
III. Weak Linkage Regulation
- Types of Regulation
Enhancer - upstream activation sequence. Binding site for transcription factor.Mutation here is cis-regulation(within the operational "cistron")
mutation in the transcription factor gene is called trans-regulation
Each type modulates activity about 50% of the time...
Evo - Devo
I. Background
II. Core Processes
III. Weak Linkage Regulation
- NOVELTY
Mutations may make an enhancer available to a different transcription factor... and now that gene is 'on' in a new tissue and can be used for a new function. Crystallins are heat-shock proteins and mitochondrial enzymes; but when they are expressed in the eye, they are used as transparent structural proteins in a completely different process.
And of course, how they are arranged in lenses vary.
Evo - Devo
I. Background
II. Core Processes
III. Weak Linkage Regulation
- NOVELTY
OR, an entirely new binding site can evolve - they are typically quite short (6-10 bases) so they will arise frequently by random mutation...selection can then favor new regulatory pathways....
KEEP THE OLD, but GAIN NEW
(sound familiar???)
- Prud'homme et al. 2006. Repeated morphological evolution through cis-regulatory changes in a pleiotropic gene Nature 440:1050-1053.
a–c, The wing spots on male flies of the Drosophila genus. Drosophila tristis (a) and D. elegans (b) have wing spots that have arisen during convergent evolution. Drosophila gunungcola (c) instead evolved from a spotted ancestor. d, Males wave their wings to display the spots during elaborate courtship dances. (Photographs courtesy of B. Prud'homme and S. Carroll.)
- Prud'homme et al. 2006. Repeated morphological evolution through cis-regulatory changes in a pleiotropic gene Nature 440:1050-1053.
yellow gene
In their previous research, they found that spotted members of both spotted clades had same cis regulatory element (CRE). So, they hypothesized that all members of the clade were descended from a spotted ancestor (99% chance ancestor was spotted - fig.)
"spotted wing"
enzyme for pigment production
- Prud'homme et al. 2006. Repeated morphological evolution through cis-regulatory changes in a pleiotropic gene Nature 440:1050-1053.
yellow gene
LOSS of the spot within this clade (an example of convergent evolution AND reversion) occurred by different mutations in same CRE.
- Prud'homme et al. 2006. Repeated morphological evolution through cis-regulatory changes in a pleiotropic gene Nature 440:1050-1053.
yellow gene
LOSS of the spot within this clade (an example of convergent evolution AND reversion) occurred by different mutations in same CRE.
Importantly, yellow is still on elsewhere. This is a pleiotropic gene that has many effects.
- Prud'homme et al. 2006. Repeated morphological evolution through cis-regulatory changes in a pleiotropic gene Nature 440:1050-1053.
yellow gene
LOSS of the spot within this clade (an example of convergent evolution AND reversion) occurred by different mutations in same CRE.
Importantly, yellow is still on elsewhere. This is a pleiotropic gene that has many effects.
Shutting it "off" by a mutation in the gene would cripple it's activity throughout the organism. Here, through cis regulation, it's expression is modulated in only one tissue (wing).
- Prud'homme et al. 2006. Repeated morphological evolution through cis-regulatory changes in a pleiotropic gene Nature 440:1050-1053.
yellow gene
In D. tristis, the yellow gene is enhanced by a completely different, independently evolved CRE.
spotted wing
- Prud'homme et al. 2006. Repeated morphological evolution through cis-regulatory changes in a pleiotropic gene Nature 440:1050-1053.
Two gains and two losses are due to independent changes in the regulation of the yellow gene.
The developmental 'scaffold' for forming spots exists... subsequent evolution of enhancement can form a new anatomical trait, which can be rapidly selected for by sexual selection.
Evo - Devo
I. Background
II. Core Processes
III. Weak Linkage Regulation
- HETEROCHRONY
- paedomorphism
- peramorphism
- allometry
All simply changes in the developmental rates of different structures or processes.
Scarabaeidae: Onthophagus
Allometry in horn length relative to body size in Beetles
Evolution of legs from fins
Evolution of legs from fins
Evo - Devo
I. Background
II. Core Processes
III. Weak Linkage Regulation
IV. Exploratory Behavior
Evo - Devo
I. Background
II. Core Processes
III. Weak Linkage Regulation
IV. Exploratory Behavior
- environmental cues affect cell activity - production of growth factors
Evo - Devo
I. Background
II. Core Processes
III. Weak Linkage Regulation
IV. Exploratory Behavior
- environmental cues affect cell activity - production of growth factors
- hypoxia - stimulates cell to produce endothelial growth factor
Evo - Devo
I. Background
II. Core Processes
III. Weak Linkage Regulation
IV. Exploratory Behavior
- environmental cues affect cell activity - production of growth factors - hypoxia - stimulates cell to produce endothelial growth factor - neighboring vascular tissue grows towards the source of growth factor
Evo - Devo
I. Background
II. Core Processes
III. Weak Linkage Regulation
IV. Exploratory Behavior
- environmental cues affect cell activity - production of growth factors - hypoxia - stimulates cell to produce endothelial growth factor- neighboring vascular tissue grows towards the source of growth factor - and BINGO... now you have vascular tissue and hypoxia is corrected
Evo - Devo
I. Background
II. Core Processes
III. Weak Linkage Regulation
IV. Exploratory Behavior
- environmental cues affect cell activity - production of growth factors - hypoxia - stimulates cell to produce endothelial growth factor- neighboring vascular tissue grows towards the source of growth factor - and BINGO... now you have vascular tissue and hypoxia is corrected - Nerves and vessels grow in response to local signals... the pattern is not hardwired.
Evo - Devo
I. Background
II. Core Processes
III. Weak Linkage Regulation
IV. Exploratory Behavior
- environmental cues affect cell activity - production of growth factors - hypoxia - stimulates cell to produce endothelial growth factor- neighboring vascular tissue grows towards the source of growth factor - and BINGO... now you have vascular tissue and hypoxia is corrected - Nerves and vessels grow in response to local signals... the pattern is not hardwired.
- So, if bone growth changes, muscles cell growth responds, and correct ennervation and vascularization occurs on this new platform.