Cellular and molecular characteristics of pollen abortion in chrysanthemum cv. Kingfisher.

KEY MESSAGE: Microspore degeneration at the tetrad stage is associated with tapetum degeneration retardation. Some genes and proteins related to cell senescence and death are the key factors for pollen abortion. Chrysanthemum (Chrysanthemum morifolium) is a major floriculture crop in the world, but pollen contamination is an urgent problem to be solved in chrysanthemum production. C. morifolium 'Kingfisher' is a chrysanthemum cultivar that does not contain any pollen in mature anthers, thus it is a very important material for developing chrysanthemum without pollen contamination. However, the mechanism of its pollen abortion remains unclear. In this study, the cellular and molecular mechanisms of 'Kingfisher' pollen abortion were investigated using transmission electron microscopy, RNA sequencing, isobaric tags for relative and absolute quantitation, and bioinformatics. It was found that the meiosis of microspore mother cells was normal before the tetrad stage, the microspores began to degenerate at the tetrad stage, and no microspores were observed in the anthers after the tetrad stage. In addition, transcriptomic and proteomic analyses showed that some genes and proteins related to cell senescence and death were identified to be implicated in chrysanthemum pollen abortion. These results indicated that the tetrad stage was the main period of pollen abortion, and the genes and proteins related to cell senescence and death contributed to pollen abortion. These add to our understanding of chrysanthemum pollen abortion and will be helpful for development of flowers without pollen contamination in the future.