Transcript labs.bio.unc.edu

Bio 261
September 30, 2003
Todd Vision
• Genetic Mapping
• “Speciation QTL” in Mimulus
• From QTL to an understanding the
evolution of species differences at a
molecular level
QTL mapping
variation in leaf-level water
use efficiency in rice
16
14
10
Lemont x Teqing
Oryza wild species
O.sativa
Rufipogon x Jefferson
IR64 x Nipponbare
More
-27.90
-28.50
Kasalath x Nipponbare
0
-28.20
13C Content
2
-28.80
-29.10
-29.40
4
-29.70
-30.00
-30.30
6
-30.60
-30.90
-31.20
8
frequency
12
McCouch et al., unpublished
rice (Kasalath x Nipponbare) WUE QTL
QTL mapping in Arabidopsis
QTL map for root length at day 6,
in liquid medium containing Aluminum
Hoekenga et al. (2003) Plant Physiol. 132:936-48.
Arabidopsis Al-tolerance
QTL both affect malate release
-What are the loci underlying speciation and
species differentiation?
- How did they arise?
- What forces have shaped them?
the genus Mimulus
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)
Isolation via pollinators and habitat in
M. lewisii vs. 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%.
lewisii
F1
F2
cardinalis
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)
Univ. of Washington
Michigan State Univ. Toby Bradshaw
Doug Schemske
Duke Univ.
John Willis
Fred Dietrich
Univ. of Montana
Lila Fishman UNC Chapel Hill
Todd Vision
CUGI
Jeffery Tomkins
comparative maps
Lycopersicon (tomato) vs. Capsicum (pepper)
Livingstone et al 1999 Genetics 152:1183
Gale & Devos 1998 PNAS 95:1972
Molecular footprint of selection
1
locus
2
3
Neutrality
Population
bottleneck
Selection
near locus 2
Schlotterer (2003) TIG 19, 32
Genomic technology
Molecular evolution and
population genetics
Molecular genetic
architecture of
species
differentiation
Field ecology
A rich and tractable
biological system