Increase in tomato locule number is controlled by two single-nucleotide polymorphisms located near WUSCHEL
Résumé
In tomato fruit, the number of locules (cavities containing seeds that are derived from carpels)varies from two to up to 10 or more. Locule number affects fruit shape and size, and is controlled by several Quantitative Trait Loci (QTLs). The large majority of the phenotypic variation is explained by two of these QTLs, fasciated and locule number (lc) that interact epistatically with one another. FASCIATED has been cloned, and mutations in the gene are described as key factors leading to the increase in fruit size in modern varieties. Here, we report the map-based cloning of lc. The lc QTL includes a 1600 bp region that is located 1080 bp from the 3’ end of WUSCHEL, which encodes a homeodomain protein that regulates stem cell fate in plants. The molecular evolution of lc showed a reduction in diversity in cultivated accessions with the exception of two SNPs. These two SNPs were shown to be responsible for the increase in locule number. An evolutionary model of locule number is proposed herein, suggesting that the fas mutation appeared after the mutation in the lc locus to confer the extreme high locule number phenotype.
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