Anomalous changes in Ca2+ATPase distribution during the process of pollen abortion in Populus tomentosa Carr.

To identify the impact of Ca2+ATPase on the pollen sterility process of woody plant, cerium trichloride (CeCl3) precipitation method and transmission electron microscopy were used to locate Ca2+ATPase in fertile and sterile anthers of Populus tomentosa Carr. The results showed that in fertile anthers, Ca2+ATPase distributed on the plasma membrane, the vacuole membrane and the endomembrane of the microspore mother cells (MMCs), as well as on the plasma membrane of tapetum cells and the endomembrane of endothecium cells. Afterwards, Ca2+ATPase decreased in the above cells and reaccumulated at the microspores and endothecium cells at the microspore and mature pollen stage. Whereas during the development of sterile anthers, Ca2+ATPase was invisible on the plasma membrane of MMCs and tapetum cells at the MMC stage, while more Ca2+ATPases were found in the outer epidermis, endothecium and middle layer cells of sterile anthers than in fertile anthers. Finally the disintegration of tapetum in sterile anthers is not complete in sterile anthers. These results suggest that anomalous distribution of Ca2+ATPase in MMCs and anther walls from sterile anther may affect the active transport of calcium, probably result in abnormal calcium accumulation, and thus affect degeneration of tapetum and normal metabolism of MMCs and endothecium cells, leading to pollen abortion.