Eukaryotic cell biology and the tree of life

Question 1

LECA and FECA

Answer 1

last and first eukaryotic common ancestor

Question 2

eukaryote specific traits

Answer 2

• Membrane chemistry from bacteria
  
  • Cytoplasmic proteome from bacteria
  • Organellar genome/proteome from bacteria
  • Informational genes from archaea
    Stuff like cellular compartmentalisation, lots of independent gene origin

Question 3

Archezoa hypothesis- main idea

Answer 3

The eukaryotic primary branch was amitochondrial. when mitochondria were acquired this created a eukaryotic lineage, but there was also the archezoa lineage which is still amitochondrial

Question 4

Archezoa hypothesis- what does it explain?

Answer 4

bacterial organelle genomes and archaeal informational genes

Question 5

Archezoa hypothesis- what does it not explain?

Answer 5

why the cytoplasmic proteome and membrane chemistry are bacterial

Question 6

Archezoa hypothesis- strenghts of the model

Answer 6

phylogenetic evidence of mitochondrial/chloroplast origin is fairly strong, so we’re pretty sure there was this crossover

Question 7

Archezoa hypothesis- issues

Answer 7

kinda sucks as a model. be neggy about it. it’s from like the 80s.

a lot of ‘amitochondriates’ actually probably did have mitochondria at some point, so this may not have been the evolutionary trajectory. mitochondrial relics v v common

Question 8

A model which does explain presence of bacterial genes in eukaryotes

Answer 8

gene transfer ratchet (‘you are what you eat’- set up by the phagotrophic origin hypothesis, idea that eating a bunch of bacterial stuff (phagotrophy) meant early eukaryotes would pick up bacterial biology (if it stayed there by selection and stuff)

Question 9

gene transfer ratchet- what does it explain?

Answer 9

pretty much everything but membrane chemistry- good explanations for why we see bacterial genes in the cytoplasmic proteome, as well as still explaining archaeal-type genes

Question 10

importance of the gene tranfer ratchet model now

Answer 10

we think phagotrophy did play a role, but possibly happened more after endosymbiosis occurred- so maybe not all that

Question 11

‘syntrhophy’ hypotheses

Answer 11

revolve around the concept that organisms interacted with each other physically and closely through stuff like metabolite transfer around the splitting off point of eukaryotes

Question 12

example of some hypotheses revolving around the syntrophy idea

Answer 12

‘inside out’ model- Baum & Baum 2014
E3 model
archaea first/syntrophy hypothesis

Question 13

what do syntrophy-based models explain

Answer 13

bacterial and archaeal protein components, does explain membrane chemistry

Question 14

what do syntrophy-based models not explain

Answer 14

not much on endomembrane system