Parthenocarpy and male sterility are highly desirable traits in tomato breeding and molecular study. The stamen carpelloid mutant generally displays male sterility. A natural mutant displaying carpelloid stamen and parthenocarpy (csp) was identified in our research group. In this study, the csp locus was finely mapped to a 65 kb interval, which contained six putative genes. One of them, Solyc04g081000, encodes the tomato class B MADS box gene TAP3 (syn. SlDEF). Sequencing data revealed that a copia long terminal repeat retrotransposon was inserted in the first intron of the TAP3 gene of the csp mutant. qRT-PCR showed that the expression of TAP3 was significantly down-regulated in the petals and stamens of the csp mutant. A phenotypic analysis of the TAP3 gene-edited mutants and allelism tests indicated that TAP3 was the gene underlying csp, and csp was a novel allelic mutation of TAP3. The results of this study will lay the foundation for a further analysis of the function of TAP3 and provide materials and a basis for a further study of the functional differentiation of tomato B-class genes.
