BMB- protists

loikiarchaeota

lead to discovery that eukaryotes arose within archaea

RNAP homologies

RBP 1-3,6,11 = bacteria and archaea

RBP 4,5,7,8,10,12 = archaea

RBP 9 = none

paradigms that protists break

one nucleus contains all genetic information, and DNA is depositary of that information

within nucleus, DNA is packaged with histones into chromatin

transcripts are monocistronic

mitochondria are for aerobic respiration

chloroplasts are for photosynthesis

there are three genomes in eukaryotic cells

ciliates - one nucleus

macronucleus = highly polyploid, transcriptionally active

micronucleus = small, diploid, transcriptionally silent during vegetative growth

ciliates sexual cycle

1. micronucleus of two cells undergoes meiosis, macronuclei destroyed

2. haploid nuclei from each partner fuse to generate diploid macronucleus

3. macronucleus develops from new micronucleus

ciliates asexual cycle

nuclei divide mitotically and cells divide by binary fission

ciliates gene elimination

elimination of some genes and amplification of others to generate macronucleus

elimination of tandem repeats and transposons, fragmentation of genome and telomere generation

excision of 60000 internal sequences

ciliates - role of RNA

experiment - no surface antigen expressed, gene present in micronucleus but gets eliminated, restore by transformation, retained by micronucleus in future sexual cycles

inactivation of specific RNAs stops corresponding DNA being retained in macronucleus

DNA rearrangements in oxytricha

eliminates sequences and unscrambles sequences to change order

depends on RNA

dinoflagellates abnormal nuclei

chromosomes remain condensed

fibrillar appearance

high content of T

high DNA content

high cation conc

no conventional histones or chromatin - westerns

histone replacement in dinoflagellates

HLPs, DVNP, histone genes

HLPs

histone like basic proteins

similar to bacterial HU proteins that coat DNA

absent from early branching dinoflagellates but present in core species

lateral transfer

DVNP

similar in sequence to DNABP from viruses that infect algae

expression in yeast impairs growth and reduces histone levels

mutations that reduce histone levels restore viability with DVNP

suggests displacement of histones with DVNP

histone genes

divergent but contain recognisable features

transcribed at low levels

poly A tail - unusual for histone RNA

trypanosomes - polycistrons

undergo trans splicing with transcript with a cap

poly A added

mitochondria alternatives

hydrogenosomes, mitosomes

hydrogenosomes

no complex III, IV or ATP synthase but has bioenergetic role

nyctotherus - remnant genome coding complex I and II

blastocysts - complex I and II and alt oxidase, mt genome encodes some of complex I

trichomonas - has complex I but no mt genome

mitosomes

no bioenergetic role

Fe-S biogenesis

e.g. giardia

dinoflagellate chloroplast genome

highly reduced - encodes some of ETC

all other genes moved to nucleus - may reduce burden of transferring full cp genome upon division

fragmented into plasmid-like circles with core involved in expression and replication

polyU tail transcripts

apicomplexa cp genome

lost photosynthesis

in plasmodium: chaperone, Fe-S biogenesis, proteins for their expression

nucleomorphs

fourth genome in cryptophytes

photosynthetic prokaryote engulfed by cell with nucleus to form chloroplast, the this was engulfed by another cell to give a cell with nucleus, nucleomorph and chloroplast

crossing 4 intracellular membranes

first membrane continuous with ER = ER targetting

second membrane = SELMA similar to ERAD

chloroplast membrane = tic and toc-like systems

diatom

chloroplast loss

replaced with whole organism = dinotom

5 genomes = 2 nuclei, 2 mt and 1 cp

mesodinium

eats cryptophytes

nucleus, nucleomorph, cp, mt, own macro and micronuclei and mt

7 genomes