An insertion of transposon in Tepi gene confers male sterility of marigold

The Asteraceae family has achieved considerable progress through the implementation of hybridization techniques. However, the special complex capitulum of its members severely hinders the breeding process. Therefore, male sterility is crucial for the hybrid seed production in Asteraceae. Here, we identified that a retrotransposon insertion in the third intron of TePI gene co-segregated with the male sterility in five F₂ segregating population of marigold (Tagetes erecta) and down-regulation of TePI gene by RNAi generated pappus-like corollas and pistil-like stamens, resulting in male sterility. The male sterile mutant showed distinct down-regulation of TePI and altered expression of other ABCE genes. The K domain of the Tepi protein was altered due to the insertion of four amino acids. Nevertheless, Tepi, like wild-type TePI, retained the capacity to form homo- and heterodimers, as well as several higher-order complexes with other floral homeotic proteins. Notably, this structural disruption specifically impaired the interaction strength between Tepi and TeAP3. Taken together, the analysis of different expression patterns and protein interaction patterns suggests that tetramer complexes determining the corolla and stamen identities may not form in male sterile plants. This research elucidates the molecular mechanism underlying male sterility in marigold and provides potential applications for hybrid breeding improvement.