Cytologic Obvervation Of Programmed Cell Death In Anther Of Cytoplasmic Male Sterile Cotton

Cytoplasmic male sterility (CMS) is very useful in the production of hybrid cotton seed and application of cotton heterosis. However, the study on mechanism of cotton CMS is not enough and should be enhanced. Although some reports indicated that CMS was related with programmed cell death of main cells in anther, there have been very little reports about programmed cell death in the cotton CMS so far. For this reason, a cytoplasmic male sterile line "Kang A" and its maintainer "Kang B" were used as material and checks to observe the ultrastructural changes of microspore mother cells and tapetal cells in anthers during the abortion process by using transmission electron microscopy. In other hand, The terminal deoxynucleotidyl transferase mediated dUTP nick end labeling reaction (TUNED , which is the unique biochemical and examination of PCD, was used to detect DNA fragment of the microspore mother cells and tapetal cells during the abortion process of CMS anther by using fluorescence microscope. Finally, combined with the results of the two experiments above, the problems whether the abortion of cytoplasmic male sterile line is related with programmed cell death were discussed. The main results were as follows:Comparing with the maintainer anther, sterile anther presented swelled mitochondria in low proportion of sporogenous cells with blurred cristae and diffused matrix. Then, the great deal of microspore mother cells degenerated with shrinkage of nucleus, fringe concentrated chromatin, more swelled mitochondria with intact outer membranes, shrinked and vacuolized protoplast, separation of protoplastic membrane and cell wall, and declined ribosome density. At meiosis stage, the MMC lost the whole structure and disaggregated gradually.TUNEL analysis showed that positive signals would be observed in sporogenous cells of CMS anther, which indicated commencement of DNA fragment process. Then, DNA fragment took place in more microspore mother cells at their forming stage and early meiosis stage. These phenotypes were extremely analogous with those of programmed cell death. Therefore, abortion of cotton anther is related with programmed cell death of MMC, suggesting that the degraded mitochondrion would release some signals and induce cell death, and vacuole played important role in digesting of protoplast.The observation of CMS tapetal cells indicated that degenerated mitochondria tookplace at first, then the whole cell was degraded mainly at meiosis stage and the central vacuole presented, finally its structure was changed as normal anther wall cells at the late meiosis stage. There was no positive signal of TUN EL in CMS tapetum during its development. The results indicated that the tapetal cell degradation and its function alteration was not a process of PCD in the sterile anther but was in the maintainer anther.