Identification of Bottle Gourd (Lagenaria siceraria) OVATE Family Genes and Functional Characterization of LsOVATE1

The OVATE gene family is a class of conserved transcription factors that play significant roles in plant growth, development, and abiotic stress, and also affect fruit shape in vegetable crops. Bottle gourd (Lagenaria siceraria), commonly known as calabash or gourd, is an annual climber belonging to the Cucurbitaceae family. Studies on bottle gourd OVATE genes are limited. In this study, we performed genome-wide identification of the OVATE gene family in bottle gourd, and identified a total of 20 OVATE family genes. The identified genes were unevenly distributed across 11 bottle gourd chromosomes. We also analyzed the gene homology, amino acid sequence conservation, and three-dimensional protein structure (via prediction) of the 20 OVATE family genes. We used RNA-seq data to perform expression analysis, which found 20 OVATE family genes to be differentially expressed based on spatial and temporal characteristics, suggesting that they have varying functions in the growth and development of bottle gourd. In situ hybridization and subcellular localization analysis showed that the expression characteristics of the LsOVATE1 gene, located on chromosome 7 homologous to OVATE, is a candidate gene for affecting the fruit shape of bottle gourd. In addition, RT-qPCR data from bottle gourd roots, stems, leaves, and flowers showed different spatial expression of the LsOVATE1 gene. The ectopic expression of LsOVATE1 in tomato generated a phenotype with a distinct fruit shape and development. Transgenic-positive plants that overexpressed LsOVATE1 had cone-shaped fruit, calyx hypertrophy, petal degeneration, and petal retention after flowering. Our results indicate that LsOVATE1 could serve important roles in bottle gourd development and fruit shape determination, and provide a basis for future research into the function of LsOVATE1.