Bio 261 September 30, 2003 Todd Vision

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Bio 261September 30, 2003Todd Vision

• Genetic Mapping
• Speciation QTL in Mimulus
• From QTL to an understanding the evolution of
  species differences at a molecular level

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QTL mapping
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variation in leaf-level water use efficiency in
rice
McCouch et al., unpublished
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rice (Kasalath x Nipponbare) WUE QTL
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QTL mapping in Arabidopsis
QTL map for root length at day 6, in liquid
medium containing Aluminum
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Arabidopsis Al-toleranceQTL both affect malate
release
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What are the loci underlying speciation and
species differentiation?- How did they
arise?- What forces have shaped them?
the genus Mimulus
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Hybrid sterility in M. guttatus vs. nasutus

• Minor QTL
• Differences in floral morphology
• Major QTL
• a pair of epistatically interacting nuclear loci
  that cause complete pollen sterility in 1/8 of
  the hybrid F2 offspring
• A cytonuclear incompatibility system causes
  complete male sterility in 1/4 of offspring
  carrying the M. guttatus cytoplasm

M. nasutus growing in a mixed clump with M.
guttatus in Shirley Creek, Calaveras Co,
California. The red lines indicate M. nasutus
flowers (photo Mark MacNair)
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Isolation via pollinators and habitat in M.
lewisii vs. cardinalis
lewisii F1 cardinalis

• Two major QTL underlying differences in
  pollination syndrome have been mapped
• Introgression of the anthocyanin QTL (yup) from
  M. cardinalis into M. lewisii reduces bee
  visitation by 80.
• Allelic substitution from M. lewisii into M.
  cardinalis at the major nectar QTL (NEC1) reduces
  hummingbird visitation by 50.

F2
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From QTL to gene

• QTL intervals contain many genes
• To get to causative polymorphisms, these things
  help
• Nearly isogenic lines (to Mendelize QTL)
• Expressed sequence tags (cDNA sequences)
• Large collections of markers (SSR, STS)
• Comparative maps (e.g. to tomato Arabidopsis)
• Large-insert clones (BAC libraries)
• Transgenics (to confirm the mapping results)

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Univ. of Washington Toby Bradshaw
Michigan State Univ. Doug Schemske
Duke Univ. John Willis Fred Dietrich
CUGI Jeffery Tomkins
Univ. of Montana Lila Fishman
UNC Chapel Hill Todd Vision
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comparative maps
Lycopersicon (tomato) vs. Capsicum (pepper)
Gale Devos 1998 PNAS 951972
Livingstone et al 1999 Genetics 1521183
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Molecular footprint of selection
Schlotterer (2003) TIG 19, 32
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Genomic technology
Molecular evolution and population genetics
Molecular genetic architecture of species
differentiation
Field ecology
A rich and tractable biological system