The Dynamic Genome Transposons

Transposable element (transposon) A sequence of DNA that is competent to move from place to place within a genome

Ds Transposition weedtowonder.org/jumpingGenes.html

Retrotransposon Content (million BP)

Transposon Caught in the Act (Burst)

Most TEs are inactive molecular “fossils”. Active TEs evolved to insert into “safe-havens.” Host sequesters Tes and regulates their movement (RNAi-based mechanism). TEs can provide advantages. (A means to rapidly reorganize the genome in response to stress.) How do organisms live with TEs?

MITE (Miniature -Inverted repeat TE) Deletion-derivative of Ping: requires Ping transposase Ping/mPing

OVER 1000 mPing copies Japonica strains mPing copy number Naito et al PNAS (2006)) mPing Over 1000 copies of mPing in 4 related strains…. Takatoshi Tanisaka lab (Kyoto University) mPing copy number in O.japonica

Genomic Distribution of mPing

UTRExonUTR Genic Distribution of mPing

mPing Alters Gene Expression

NipponbareEG4 mPing Confers Salt Tolerance

Naito et al, Nature, 2009 Massive amplification largely benign Subtle impact on the expression of many genes Produces stress-inducible networks (cold, salt, others?) Generates dominant alleles Rapid mPing amplification (burst)

Transposons and Zapotec Oral Tradition Virigina Walbot Fields of those who who steal Zapalote Chico maize will be poisened Transcription of intact Mutator transposase repressed by homozygous inhibitor Outbreeding releases repression Mutator activation results in sterility (hybrid dysgenesis) Analogous to P elements in fruit flies

(relatively) simple incredibly abundant evolve rapidly promote rapid genome evolution largely ignored (discovery) TEs for Student Research Projects