Bio 261September 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

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13C Content

Kasalath x Nipponbare

Lemont x Teqing

Oryza wild species

O.sativa

Rufipogon x Jefferson

IR64 x Nipponbare

variation in leaf-level water use efficiency in rice

McCouch et al., unpublished

rice (Kasalath x Nipponbare) WUE QTL

QTL mapping in Arabidopsis

Hoekenga et al. (2003) Plant Physiol. 132:936-48.

QTL map for root length at day 6, in liquid medium containing Aluminum

Arabidopsis Al-toleranceQTL 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 cardinalis

F2

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)

Duke Univ. John Willis

Fred Dietrich

Univ. of Washington Toby Bradshaw

CUGI Jeffery Tomkins

UNC Chapel HillTodd Vision

Michigan State Univ. Doug Schemske

Univ. of MontanaLila Fishman

comparative maps

Livingstone et al 1999 Genetics 152:1183Gale & Devos 1998 PNAS 95:1972

Lycopersicon (tomato) vs. Capsicum (pepper)

Molecular footprint of selection

Neutrality

Populationbottleneck

Selectionnear locus 2

locus1 2 3

Schlotterer (2003) TIG 19, 32

Genomic technologyMolecular evolution and

population genetics

Field ecologyA rich and tractable biological system

                      

            

Molecular genetic architecture of

species differentiation