A cryptic variation in a member of the Ovate Family Proteins is underlying the melon fruit shape QTL fsqs8.1 |
Melon cultivars have a wide range of fruit morphologies. Quantitative trait loci (QTL) have been identified underlying such diversity. This research focuses on the fruit shape QTL fsqs8.1, previously detected in a cross between the accession PI 124112 (CALC, producing elongated fruit) and the cultivar ‘Piel de Sapo’ (PS, producing oval fruit). The CALC fsqs8.1 allele induced round fruit shape, being responsible for the transgressive segregation for this trait observed in that population. |
Cecilia Martínez-Martínez, Maria José Gonzalo, Pablo Sipowicz, Manuel Campos, Irene Martínez-Fernández, Carmen Leida, Mohammed Zouine, Konstantinos G. Alexiou, Jordi Garcia-Mas, María Dolores Gómez, Pablo Tornero, Miguel Ángel Pérez-Amador, Cristina Esteras, Belén Picó, Carlos Romero & Antonio J. Monforte Theoretical and Applied Genetics; March 2022; vol. 135: 785–801 Key messageThe gene underlying the melon fruit shape QTL fsqs8.1 is a member of the Ovate Family Proteins. Variation in fruit morphology is caused by changes in gene expression likely due to a cryptic structural variation in this locus. AbstractMelon cultivars have a wide range of fruit morphologies. Quantitative trait loci (QTL) have been identified underlying such diversity. This research focuses on the fruit shape QTL fsqs8.1, previously detected in a cross between the accession PI 124112 (CALC, producing elongated fruit) and the cultivar ‘Piel de Sapo’ (PS, producing oval fruit). The CALC fsqs8.1 allele induced round fruit shape, being responsible for the transgressive segregation for this trait observed in that population. In fact, the introgression line CALC8-1, carrying the fsqs8.1 locus from CALC into the PS genetic background, produced perfect round fruit. Following a map-based cloning approach, we found that the gene underlying fsqs8.1 is a member of the Ovate Family Proteins (OFP), CmOFP13, likely a homologue of AtOFP1 and SlOFP20 from Arabidopsis thaliana and tomato, respectively. The induction of the round shape was due to the higher expression of the CALC allele at the early ovary development stage. The fsqs8.1 locus showed an important structural variation, being CmOFP13 surrounded by two deletions in the CALC genome. The deletions are present at very low frequency in melon germplasm. Deletions and single nucleotide polymorphisms in the fsqs8.1 locus could not be not associated with variation in fruit shape among different melon accessions, what indicates that other genetic factors should be involved to induce the CALC fsqs8.1 allele effects. Therefore, fsqs8.1 is an example of a cryptic variation that alters gene expression, likely due to structural variation, resulting in phenotypic changes in melon fruit morphology.
See: https://link.springer.com/article/10.1007/s00122-021-03998-6
Figure 1: High-resolution mapping of fsqs8.1. A schematic representation of the reference genome V4.0 (Castanera et al. 2020) based on the double haploid line DHL92 is depicted in the upper part of the figure, indicating the position of markers, annotated genes and the repetitive sequence rich region. The length of the genes and the direction of the transcription are indicated with arrows. The deduced genome of CALC8-1 based on re-sequencing data is depicted in the lower part. Blue dashed lines indicates the large deletions observed in CALC8-1. The position of fsqs8.1 based on the fine mapping experiments is indicated below the CALC8-1 genome. The candidate MELO3C025206 is highlighted in green. On the right, typical fruits of PI 124,112 (CALC, donor parent), PS (recipient parent) and CALC8-1 (introgression line carrying the fsqs8.1 locus from CALC in PS background) are also shown) (color figure online)
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