Biopolym. Cell. 2019; 35(3):206-207.
Chronicle and Information
Structural reorganization of nuclei of wheat antipodal cells during programmed cell death
- Lomonosov Moscow State University
- Russian Institute of Agricultural Biotechnology
The endosperm is an important part of definitive seed. It is known that endosperm cannot normally develop in embryo sac with defective antipodal complex. The antipodal complex is located between the endosperm and the maternal tissues of ovule. The main function of antipodal cells with polytene chromosomes is synthesis of substances for the formation and protection of endosperm syncytium. The antipodal cells of Poaceae pass through consecutive stages of proliferation, differentiation and death. During their differentiation, antipodals nourish the emerging endosperm and the endosperm cellularization induces antipodal cell death. Speculated, the functioning of polyploid antipodal cells gives Poaceae an evolutionary advantage over other plants, because Poaceae is a most widespread group of plants on the Earth. Moreover, antipodal complex is a unique model for understanding the structure of polytene chromosomes. The aim of our work was to study the morphology of the nuclei of antipodal cells isolated from fertilized ovules (containing an inducer of cell death, endosperm) and unfertilized ovules (without endosperm) at different stages of programmed cell death. The work was performed on total specimens of embryo sacs isolated from fixed wheat ovules. We used methods of light microscopy (DAPI staining, acridine orange staining, Ag-Nor staining, immunocytochemical staining by the antibodies to fibrillarin, TUNEL assay) and transmission electron microscopy. We demonstrated that in fertilized embryo sacs during the differentiation, individual giant polytene chromosomes are formed in the nuclei of antipodal cells. During the death, chromosomes become more condensed and come together. Components of nucleoli segregate into the cavities of chromosomes, chromosomes become indistinguishable. Some nuclei can be strongly flattened and oblong. Dense chromatin of some nuclei may be fragmented. Then antipodal cells strongly converge and are absorbed by the endosperm. In the nuclei of antipodal cells from unfertilized embryo sacs, individual chromosomes can be detected at the stage of differentiation. During the death, chromosomes condense, in some cells, chromosomes come together, but complete integration of all chromosomes does not occur. In some nuclei, fragmentation of chromatin takes place, in others degradation of chromatin is observed in the central region of the nucleus. Segregation of the nucleolar components does not occur; nucleoli remain intact longer than the chromatin. Nuclei of antipodals from fertilized and unfertilized embryo sacs at the stage of the death are TUNEL-positive. To sum up, the morphology of the antipodal nuclei from fertilized and unfertilized ovules differs and has its own features.