Targeted Editing and Phenotypic Profiling of CmOFP13 Mutants Reveal Its Role in Melon Fruit Morphogenesis.

The melon fruit shape is a trait that influences storage as well as consumer preference. Fruit shape is known to be regulated by factors such as Ovate Family Proteins (OFPs), Tonneau Recruiting Motif proteins (TRMs), IQ67 domain proteins (IQDs) and plant hormones. CmOFP13 (MELO3C025206) had been identified as a regulator of shape in melon using a map-based cloning approach and validated by overexpression in Arabidopsis, generating plants with rounder leaves and shorter siliques. In this work, CRISPR-Cas9 was applied in melon for the functional validation of CmOFP13. 'Védrantais' (VED) seed cotyledons were transformed, obtaining diploid edited plants with a slightly elongated phenotype compared to the wild type in both ovaries and fruits. This effect is associated with the presence of larger cells in the distal area of E1 stage flowers. The analysis of the mutation indicated the loss of the OVATE domain in the edited CmOFP13, while maintaining the DNA-binding domain. In addition, new candidate genes have been proposed based on phylogenetic analyses and expression data. The mutation of OFPs offers the possibility of new melon fruit shapes, adapting the fruit for safer storage or to consumer demands.