Blackman, Benjamin K. , Rasmussen, David R. , Burke, John M. , Knapp, Steve J. , Michaels, Scott D. , Rieseberg, Loren H. .
Identification of an FT paralog as a domestication gene in sunflower.
We have undertaken a comprehensive candidate gene approach utilizing map location, gene expression, and gene sequence information to identify genes contributing to variation in flowering time between wild and domesticated sunflower (Helianthus annuus). Thirty preliminary candidates orthologous to genes known to regulate flowering time in model organisms were incorporated into the sunflower genetic map. For genes that co-localize with QTL previously identified in crosses between wild and domesticated sunflower, we looked for notable differences in gene expression and cDNA sequence between cross parents. Candidate genes meeting these multiple criteria were then resequenced from a large diversity panel of elite-bred, landrace, and wild populations to determine if they show a signature of selection with domestication or subsequent improvement.
This targeted candidate gene pursuit has revealed clear involvement of at least one member of the FT gene family, which maps to a genomic region containing a major QTL for flowering time. Strikingly, the domesticate parentís allele contains a frameshift mutation that alters half the protein sequence. NILs constructed for the QTL show the region has photoperiod-dependent effect on phenotype, with the plants carrying the wild allele flowering earlier than plants carrying the domestic allele. These observations are consistent with the predicted gene function as FT expression is induced by photoperiod and the domestic allele carries the loss of function mutation. Notably, this frameshift allele is nearly exclusively found in elite-bred and landrace domesticated accessions while in-frame alleles are nearly exclusively found in wild populations. These findings suggest that we have identified a functional difference between domesticated and wild sunflower that was swept to fixation during early domestication.
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1 - Indiana University, Bloomington, Biology, 1001 East Third Street, Bloomington, IN, 47405, USA
2 - University of Georgia, Department of Plant Biology, Miller Plant Sciences Bldg., Athens, Georgia, 30602, USA
3 - University of Georgia, Crop and Soil Sciences, Center for Applied Genetic Technologies, 111 Riverbend Road, Athens, GA, 30602, USA
4 - Indiana University, Biology, 1001 East Third Street, Bloomington, Indiana, 47405, USA
5 - University of British Columbia, Botany Department, 3529-6270 University Boulevard, Vancouver, British Columbia, V6T 1Z4, Canada
candidate gene approach
Presentation Type: Oral Paper:Papers for Sections
Location: 182/I K Barber
Date: Monday, July 28th, 2008
Time: 8:00 AM