| Carpel is the predecessor of the fruit, and is crucial for fruit development and quality. Grape fruits generally contain two carpels which encloses two ovules respectively. However, a few cultivers produce fruits with three or four carpels in natural condition. Comparing to the two carpels, Fruit size, bunch weight and yield of multiple carpels are be improved. However, there are few reports about the mechanism of carpel development, and the study for this mechanism will offer the insights into fruit formation. In this work,’Xiangfei’grapevine was used as the plant material because of its high occurrence for tricarpelate. The ontogeny patterns of bi-and tricarpellate ovaries in’Xiangfei’ grapevine were investigated, and the relationship between the occurrence rate of tricarpellate ovaries and the expression level of gene VvYABBY5 was investigated. The major results are summarized as follows:1. Paraffin section was used to observed the formation process of carpel, and the results showed that different fusion mechanisms may exist in the formation of tricarpelate. In ’Xiangfei’ grapevine, which has high tricarpelate occurrence, congenital fusion is the main pathway for tricarpellate ovary ontogeny. The result of appearance and paraffin section showed that tricarpellate fruits were bigger than bicarpellate fruits, and the number of seeds was also more in tricarpelate.2. Transcriptome data of ’Xiangfei’ bi-and tricarpellate ovaries from anthesis was obtained using Illumina sequencing, and 165 differentially expressed genes (DEGs) were detected. Among those DEGs, there were 50 up-regulated and 115 down-regulated genes. Nine DEGs, which may affect tricarpellate ovary development were identified based on Gene Ontology (GO). Real time PCR result showed that the expression of VvAGAMOUS1(AG1), VvAPETALA1(AP1), VvAPETALA2(AP2), VvCLAVATA1(CLV1), VvCLAVATA2(CLV2), VvSEPALLATA3(SEP3) and VvSPATULA(SPT) were higher in tricarpelate, while the expression level of VvYABBY5(VvYAB5) and VvWUSCHEL-related homeobox HWOX1) were higher in bicarpelate. VvYAB5 and FASCIATED(FAS negative controls the formation and development of multi-locules) are both YABBY family members.3. To clarify whether other YAB genes influenced the development of tricarpelate, four YAB genes were blasted in ’Xiangfei’ grapevine. By means of semi-quantitative RT-PCR, we investigated the expression patterns of VvYABBY-1,2,4,5 in various organs of grapevine. The analysis showed that VvYAB4 was not detected in roots, stems,leaves, tendril and ovaries. Real-time PCR was used to analysis the expression of VvYAB1, VvYAB2 and VvYAB5 in bi-and tricarpellate ovaries. The results showed that VvYAB2 and VvYAB5 have similar expression patterns in different ovary development period, and transcript of VvYAB5 in tricarpellate ovaries was-2-fold lower. In situ study of VvYAB5 showed that the transcripts of VvYAB5 detected in carpel primordial, and during the development of ovary, the hybridization signal could be detected in placental tissue in bicarpelate and inside ovary wall in tricarpelate. The result indicated that FvYAB5 participate in the development process of tricarpellate ovaries. We analyzed the methylation level of VvYAB5 gene promoter in bi-and tricarpellate ovaries, but no difference was found.Yeast 2-hybrid was used to analyze the interactions between VvYAB5 and other eight DEGs. VvYAB5 was found to have extensive interactions with VvAG1, VvSEP3 and VvWUS. These results suggested that the formation of VvYAB5-VvAG1, VvYAB5-VvSEP3 and VvYAB5-VvWUS heterodimers are essential in the process of tricarpellate ovaries development.Collectively, this study demonstrated that congenital fusion is the main pathway for tricarpellate ovary ontogeny in ’Xiangfei’ grapevine. Comparing to thebicarpelate, fruit size and seed number of tricarpelate are improved. VvYAB5 could participate in the development of tricarpellate ovaries, and the formation of VvYAB5-VvAG1, VvYAB5-VvSEP3 and VvYAB5-VvWUS heterodimers may regulate the development of tricarpellate. |
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