Expression and Functional Analysis of the ABORTED MICROSPORES (AMS) Gene in Marigold (Tagetes erecta L.)

Male sterility is an important trait in heterosis utilization and marigold (Tagetes erecta L.) breeding. Currently, most male-sterile lines used in production are derived from natural mutations. ABORTED MICROSPORES (AMS) is an important gene that regulates tapetum and microspore development. Therefore, the effect of AMS on fertility was studied. TeAMS was located in the nucleus and exhibited self-activation activity. TeAMS was highly expressed in the flower buds of T. erecta. The expression of this gene in fertile plants was higher than that in sterile plants, and the expression level gradually increased with the development of flower buds. The expression level of TeAMS was highest in the flower buds with a diameter of 1.2 cm at the floret differentiation stage, while the expression level was extremely low in the flower buds with a diameter of 1.6 cm. The expression trend of TeAMS in sterile plants was opposite to that in fertile plants. At the inflorescence primordium differentiation stage, flower buds with a diameter of 0.2 cm had the highest expression level, and the stem tip had the lowest expression level. In tobacco (Nicotiana tabacum L.), overexpression of the TeAMS gene resulted in shortened floral tubes, increased thousand-seed weight, a reduced flowering period, and decreased flower numbers. The pollen viability of transgenic tobacco was significantly lower than that of the wild type, and the pollen grains were smaller and showed irregular shapes. The pollen wall was dry and shrunk. Some pollen germinal furrows were distorted, and a few were almost invisible. Silencing TeAMS resulted in a longer flowering period in tobacco, reduced thousand-seed weight, and high pollen viability. Pollen morphology in silenced lines showed no significant differences compared to the wild-type and empty vector controls. Only a few pollen grains were smaller, shriveled, and shrunken. Therefore, the TeAMS gene plays an important role in regulating the fertility of marigolds. This study provides a theoretical foundation for breeding marigold male-sterile lines.