Ovule abortion accompanied by programmed cell death in Castanea mollissima

Abstract

Chinese chestnut (Castanea mollissima Blume.) ovary contains 12-18 ovules, but only one can develop and grow normally, which indicates that the abortive rate of ovules can go as high as 94%. In this study, we observed the developmental characteristics and cytological changes of abortive ovules and fertile ovules during development. Morphological analysis showed it would take about 15∼20 days from globular to cotyledon embryo in fertile ovules, which is accompanied with the formation and apoptosis of endosperm. But there were stark differences in the nutrient transport, microstructure and ultrastructure of fertile and abortive ovules. The fluorescence disodium fluorescein and FDA indicated that all ovules were viable at early stages, but some ovules became inactive at different times as the ovary developed. Fluorescence labelling and ultrastructure showed cell nuclei of abortive ovules were disintegrated at 25 days after anthesis (DAA). Compared with the fertile ovules, starch grains were synthesized at earlier periods, but disappeared immediately, and the cells were usually irregular in shape, and had folded cell membranes in the abortive ovules. Furthermore, the Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) was carried out to assess programmed cell death in fertile and abortive ovules, results showed that DNA fragmentation was occurred in the cells of abortive ovules. In short, these results provide new insights into ovule abortion in the angiosperm.