Download
1 / 41
410 likes | 546 Views
Mi öröklődik a géneken kívül?. Szathmáry Eörs. Collegium Budapest . Eötvös University. Units of evolution. multiplication heredity variation. hereditary traits affecting survival and/or reproduction. The formose ‘reaction’. formaldehyde. autocatalysis. glycolaldehyde. Butlerow, 1861.
E N D
Mi öröklődik a géneken kívül? Szathmáry Eörs Collegium Budapest Eötvös University
Units of evolution • multiplication • heredity • variation hereditary traits affecting survival and/or reproduction
The formose ‘reaction’ formaldehyde autocatalysis glycolaldehyde Butlerow, 1861
Classification of replicators Limited (# of individuals) (# of types) Unlimited (# of individuals) << (# of types)
King (1980): evolution of the coenzymes He looked at the metabolic maps then Coenzymes looked auto- and cross-catalytic BUT the situation is slightly more complicated The idea nicely links to the assumed primitive ancestry of coenzymes (related to the idea of the RNA world)
Although A is autocatalytic, it is not strictly needed Dependent on the environment!
Autocatalysis of the pair (A, B) is more complicated, but easy to see
The basic question Could one kick-start metabolism just with external molecules and macromolecules (genes an enzymes)? Influx buildup of metabolism?
Yeast and fungal amyloid prions • The soluble forms of the yeast proteinsUre2p and Sup35p function in nitrogen regulation and transcription termination,respectively. • Their amyloid forms are non-functional. Soluble Rnq1p has no knowncellular function and the amyloid form can sporadically prime polymerization of Sup35por Ure2p resulting in the generation of the [PSI+] and [URE3] prions. • The soluble form ofthe HETs protein has no known function, but its amyloid form is necessary forheterokaryon incompatibility, which is a limitation on the fusion of neighbouringcolonies. • Red domains are apparently unstructured in the native form and becomeamyloid in the prion form. Green shapes are natively structured domains.
Epigenetic inheritance Structural inheritance (e.g. cortical inheritance in ciliates) Autocatalytic gene activity Chromatin marking (e.g. methylation)
Regulation of gene expression by constitutive expression of a protein After division the state is inherited because enough protein is around
Linaria (gyújtoványfű) A naturally occurring mutant ofLinaria vulgaris, originally described more than 250 years ago byLinnaeus, in which the fundamental symmetry of the flower ischanged from bilateral to radial. The mutant carriesa defect in Lcyc, a homologue of the cycloidea gene which controlsdorsoventral asymmetry in Antirrhinum. The Lcyc gene is extensivelymethylated and transcriptionally silent in the mutant. Thismodification is heritable and co-segregates with the mutantphenotype. Occasionally the mutant reverts phenotypicallyduring somatic development, correlating with demethylation ofLcyc and restoration of gene expression. It is surprising that the first natural morphological mutant to be characterized shouldtrace to methylation, given the rarity of this mutational mechanism in the laboratory. This indicates that epigenetic mutationsmay play a more signi®cant role in evolution than has hithertobeen suspected.
Hypermutation in derepressed operons Starvationfor leucine in an Escherichia coli auxotroph triggersmetabolic activities that specifically target the leu operon forderepression, increased rates of transcription, and mutation. Derepression of the leu operon was a prerequisite for itsactivation by the signal nucleotide, guanosine tetraphosphate,which accumulates in response to nutritional stress (thestringent response). A quantitative correlation was establishedbetween leuB mRNA abundance and leuB2 reversionrates. These investigationssuggest that guanosine tetraphosphate may contributeas much as attenuation in regulating leu operon expressionand that higher rates of mutation are specifically associatedwith the derepressed leu operon.
Language is not Weismannian protein protein germ DNA DNA soma soma sentence sentence germ germ germ Neural representation Neural representation germ
RNA-directed DNA methylation • Target loci (in this case tandemlyrepeated sequences; coloured arrows) recruit an RNA polymerase IVcomplex consisting of NRPD1A and NRPD2 through an unknownmechanism, and this results in the generation of a single-stranded RNA(ssRNA) species. • This ssRNA is converted to double-stranded RNA(dsRNA) by the RNA-dependent RNA polymerase RDR2. The dsRNAis then processed into 24-nucleotide siRNAs by DCL3. The siRNAs aresubsequently loaded into the PAZ- and PIWI-domain-containing proteinAGO4, which associates with another form of the RNA polymerase IVcomplex, NRPD1B–NRPD2. AGO4 that is ‘programmed’ with siRNAscan then locate homologous genomic sequences and guide the proteinDRM2, which has de novo cytosine methyltransferase activity. • Targeting ofDRM2 to DNA sequences also involves the SWI–SNF-family chromatinremodellingprotein DRD1. The NRPD1B–NRPD2 complex mightgenerate a target transcript (ssRNA) to which the AGO4-associated siRNAscan hybridize. • Given that siRNAs homologous to some loci are absent indrm2 mutants and ago4 mutants, it is possible that DNA methylation (bluecircles) also stimulates siRNA generation and reinforces silencing.
PcG-protein-mediated silencing throughout the A. thaliana lifecycle • a, FLC is transcriptionally active in seedsand seedlings, preventing the plant from flowering and prolongingvegetative development. • b, Exposure to a long period of cold (that is,vernalization) results in the expression of VIN3 (red), which initiatesrepression of FLC transcription, and the binding of the PcG protein VRN2,as well as VRN1 and LHP1 (blue). In this process, chromatin at FLC isepigenetically modified by the trimethylation of H3K27. • c, After warmertemperatures return, FLC repression is maintained, allowing flowering tobe induced by other cues. • d, During flower development, the anthers • and ovaries are sites of meiotic differentiation, giving rise to haploidcells known as microspores and megaspores, respectively. • e, Thesemeiotic products undergo mitotic proliferation to form the multicellularembryo sac and pollen gametophytes. • f, PcG-protein-mediatedrepression at FLC is removed during an undefined resetting process. • g, Then, the pollen contributes sperm nuclei to the embryo sac, and thesefertilize the haploid egg cell and diploid central cell (not shown), formingthe embryo and endosperm (respectively) in a new seed, in which FLC isre-expressed.
Chimpanzee culture • Each chimpanzee community has its own unique array of traditions that together constitute the local‘culture’. • ‘Customary’ acts are those typical in the community, ‘habitual’ones are less common but consistent with social transmission, and ‘absent’acts are those missing with no apparent straightforward environmentalexplanation. • Traditions are defined as behaviour patterns that arecustomary or habitual in at least one site but absent elsewhere. • Transmissionis attributed to social learning on the basis of a complex of circumstantialevidence, ranging from intense observation by juveniles to distributions inconsistent with alternative explanations.
The different social conventions of neighbours: the grooming hand-clasp
Why is language so interesting? Because everybody knows that only we talk …although other animals may understand a number of words Language makes long-term cumulative cultural evolution possible A novel type of inheritance system with showing “unlimited hereditary” potential
Design features of language Compositionality (meaning dependent on how parts are combined) Recursion (phrases within phrases) Symbolicism (versus icons and indices) Cultural transmission (rather than genetic) SYMBOLIC REFERENCE and SYNTAX
Three interwoven processes Note the different time-scales involved Cultural transmission: language transmits itself as well as other things, has its own dynamics
