Identification of CaPCR1, an OFP gene involved in pointed vs. concave fruit tip regulation in pepper (Capsicum annuum L.) using recombinant inbred lines

Abstract

The concave shape of the fruit tip in pepper plants is highly susceptible to drought and low temperature stresses, resulting in the appearance of a pointed tip fruit, which affects its commercial value. However, few studies on the process of fruit tip development and regulatory genes in pepper have been reported. Herein, the developmental process of the ovary before flowering, especially changes in the shape of the ovary tip, was studied in detail. The results showed that the final fruit tip shape was consistent with the ovary tip shape before flowering, and a concave tip shape gradually developed. F4 recombinant inbred lines (RILs) were constructed to map the genes regulating fruit tip shape through hybridization of the LRS and SBS pepper inbred lines. CaPCR1 (Capana12g002165), an OFP (OVATE Family Protein) family gene, was located in the candidate region on chr12. Three SNPs were found in the protein coding sequence of CaPCR1 between SBS and LRS, but only one SNP led to amino acid variation. Sequence variations, including base replacements, deletions and insertions, were also detected in the gene promoter region. The relative expression level of the CaPCR1 gene was significantly greater in the concave tip ovary than in the pointed tip ovary. qRT‒PCR analysis revealed that the CaPCR1 gene was expressed mainly in the gynoecium, placenta and green fruit pericarp, which was consistent with its function in ovary and fruit development. Taken together, these results suggested that CaPCR1 is a candidate gene involved in fruit tip shape determination in pepper.