Dissecting the genetic basis of primary seed dormancy in arabidopsis thaliana
Résumé
Seed dormancy is likely to be an important adaptive trait as it determines the right timing of seed germination. Even if several QTLs (Quantitative Trait Locus) have been identified in previous studies, it remains difficult to fully understand the genetic basis of natural variation for this trait in A. thaliana. We have found great variation for primary seed dormancy in a set of 300 Swedish accessions and we observed a strong correlation between this trait and latitude and climatic variables such as temperature and precipitation. All northern accessions seem to be non dormant whereas most of those from the south exhibit a strong primary seed dormancy.
GWAS (Genome Wide Association Studies) for primary seed dormancy on a subset of 163 accessions revealed a complex 50-kilobase region encompassing the well-known gene DOG1 (Delay Of Germination 1) and at least 3 other interesting candidate genes. Although DOG1 has been reported to be one of the major seed dormancy genes, neither its function nor the causal polymorphism underlying variation in seed dormancy is known. We were able to narrow down the region of interest and we identified at least 2 candidate SNPs (Single Nucleotide Polymorphism) in the DOG1 cis regulatory region. Based on these findings, we looked at DOG1 haplotype structure and we found at least 17 haplogroups showing strong correlation with primary seed dormancy levels. Moreover, the presence of several haplotypes leading to the same dormancy phenotypes provides support for the idea of allelic heterogeneity, which could explain the complex signature of the DOG1 locus that we observed in our initial GWAS. We are currently working on the functional validation of these results.