15th International Conference on Arabidopsis Research - TAIR

T06-011
Mapping Quantitative Trait Loci governing flowering
time in Arabidopsis using Stepped Aligned
Recombinant Inbred Strains(STAIRS)
S A C N Perera(1), T M Wilkes(1), M J Kearsey(1)
1-School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2 TT, UK
Mapping Quantitative Trait Loci governing flowering time in Arabidopsis
thaliana using Stepped Aligned Recombinant Inbred Strains (STAIRS).
The majority of genetic variation in plants and animals is quantitative and
multifactorial in nature with individual traits being under the control of a
number of genes. Mapping such quantitative trait loci (QTL) is extremely
important for trait manipulation in plant breeding programs. A major problem
in QTL mapping is that the confidence intervals associated with their location
are frequently large (10-30 cM) making it difficult to identify candidate
genes. The objective of our current research is to test the feasibility of a novel
approach based on ‘chromosome engineering’ for identifying the source and
underlying nature of allelic variation at individual QTL. We are using a specially
generated resource collection of Arabidopsis thaliana lines, designed for
fine gene mapping across the whole genome.
This resource consists of individual Chromosome Substitution lines (CSS)
and the associated Stepped Aligned Inbred Recombinant Strains (STAIRS)
(Koumproglou et.al, 2002). QTL analysis studies using STAIRS have indicated
the presence of significant flower QTL in the top 20 cM of chromosome 3.
In order to further define the region we used a marker assisted backcross
breeding program to generate additional STAIRS, which differ in introgression
size by 1 cM within the region of interest. We have started plant house trials
with the refined STAIRS for the quantitative genetic analysis, which is expected
to reveal the location of the relevant QTL with greater precision. Gene
expression profiling and allele sequence analysis are planned at the moment
to study the nature and action of the genes involved.
Koumproglou et. al. (2002) High-resolution QTL analysis using STAIRS in Arabidopsis. Plant
Journal 31(3) 355-364
T06 Natural Variation and Comparative Genomics Including Genome
T06-012
Evolutionary potential of the chalcone synthase cisregulatory
region in Arabidopsis thaliana
de Meaux Juliette(1), Goebel Ulrike(1), Pop Ana(1), Mitchell-Olds Tom(1)
1-Department of Genetics and Evolution, Max Planck Institute of Chemical Ecology, Hans Knöll Str
8, 07745 Jena Germany
Cis-regulatory domains can evolve rapidly because the multiple transcription
factor binding sites they harbour are often short and redundant. However,
little is known about the adaptive evolution of these sequences over short
evolutionary time scales. The cis-regulatory region of chalcone synthase
(CHS), a key enzyme in the flavonoid pathway, offers a good opportunity to
examine this question, because it is one of the best known promoters in
plants. Phylogenetic footprinting across Brassicacae species has highlighted
the presence of several conserved DNA regions which confer light-responsive
expression.
Using pyrosequencing, we have developed an allele specific assay to examine
cis-regulatory variation for the CHS gene in A. thaliana. We correlate the
observed functional variation with within-species nucleotide polymorphisms
in the promoter region of the gene. The distribution of nucleotide variation in
the promoter does not depart from neutral expectations indicating that selection
has not affected diversity in this region. Nonetheless we have identified
three groups of promoter alleles that are functionnaly differentiated with
respect to light response. These allelic groups could provide different selective
advantages in certain environmental conditions. Thus, our results indicate
that the CHS promoter has a potential for functional evolution. Furthermore,
the sequence survey suggests that this potential can result from a limited
number of mutations and further supports the hypothesis that cis-regulatory
variation can significantly contribute to rapid adaptation.
15 th <strong>International</strong> <strong>Conference</strong> on Arabidopsis Research 2004 · Berlin