Transcript Plant Transposons

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)
How do organisms live with TEs?
• 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.)
Ping/mPing
MITE (Miniature -Inverted repeat TE)
Deletion-derivative of Ping: requires Ping transposase
mPing copy number in O.japonica
OVER 1000 mPing copies
mPing
Japonica strains
Over 1000 copies of mPing in 4 related strains….
Naito et al PNAS (2006))
Takatoshi Tanisaka lab (Kyoto University)
Genomic Distribution of mPing
Genic Distribution of mPing
12
shared
(n=926)
10
unshared
(n=736)
(%)
8
expect.
6
4
2
0
5'UTR
exon
UTR
Exon
intron
3'UTR
UTR
mPing Alters Gene Expression
Os02g0135500 (-41)
2.5
NB
EG4 (mPing+)
A123 (mPing+)
A157
2
1.5
1
0.5
0
control
cold
salt
dry
mPing Confers Salt Tolerance
Nipponbare
EG4
Rapid mPing amplification (burst)
• Massive amplification largely benign
• Subtle impact on the expression of many genes
• Produces stress-inducible networks (cold, salt, others?)
• Generates dominant alleles
Naito et al, Nature, 2009
Transposons and Zapotec Oral Tradition
• 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
Virigina Walbot
• sterility (hybrid dysgenesis)
• Analogous to P elements in fruit flies
TEs for Student Research Projects
• (relatively) simple
• incredibly abundant
• evolve rapidly
• promote rapid genome evolution
• largely ignored (discovery)