#Studer et al.
tb1 is a QTL for tillering
represses lateral organ growth
previous work mapped causative locus to ~60kb upstream of tb1 ORF. implying ? enhancer
Made big mapping pop, isolated recombinants in this region: how ? Dense array of markers in region, look for CO
Found 18 COs in region, made each homozygous by selfing
Two different components to region that affect phenotype differently
lower diversity in maize than teo suggests ? selection on maize
lower diversity in this region in teosinte vs. other regions suggests ? functional constraint which means ?
(show figure)
HKA test: compare diversity to difference from outgroup. if low diversity due to mutation, should be fewer differences. but if see large differences (implying high mutation) then low diversity is surprising
Tested frequency of these in maize and teosinte more broadly: what do you predict ? Should be nearly fixed. That is what they found (>95% maize)
How old are these insertions? Used data from the sequence of the TE to estimate age: 20K years. So since maize was domesticated 10K years ago, what does this say? Not a new mutation, but one that was already in teosinte!
Evidence for selection combined w/ fine-mapping limits area for causative mutation
In this regions, only 4 differences between maize and teosinte.:
- 2 SNPs
- two TEs: a MITE (nonautonomous DNA transposon) & a larger Helitron (LTR retro)
Tested each in transient assay (enhancer bashing). (NOS terminator stops transcription)
Distal represses expression, but with or without MITE
Proximal enhances expression, but only with HOPSCOTCH