The pollen wall and tapetum are altered in the cytoplasmic male sterile line RC₇ of Chinese cabbage (Brassica campestris ssp pekinensis).
Cytoplasmic male sterile line RC(7) of Chinese cabbage produces mature anthers without  pollen. To understand the mechanisms involved, we examined the ultrastructural  changes during development of the microspores. Development of microspores was  not affected at the early tetrad stage. During the ring-vacuolated period, some  large vacuoles appeared in the tapetum cells, making them larger, extending to  the anther sac center during the monocyte period. At the same time, the tapetum  degenerated as the microspores aborted, resulting in pollen-deficient anthers.  As a result, the locules collapsed and the anthers shriveled. The callose was  degraded in the pollen walls; abnormal deposits of electrodense material gave  rise to irregular spike-shaped structures, rather than the characteristic  rod-like shape of the B7 bacula. The internal intine wall of RC(7) was thinner than that of the B7 type. At the mitosis I  microspore stage, the tapetum cells contained multiple plastids, with numerous  small spherical plastoglobuli, and lipid bodies. Based on these observations,  we suggest that RC(7) abortion may be due to mutated genes  that normally regulate development of the pollen wall and cell walls in the RC(7) line.
College of Horticulture, Northwest A & F University, Yangling, Shaanxi, China.
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Zhao
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Huang
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Ahmed
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Gong
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Zhao
D017209:Apoptosis; D001937:Brassica / Q000235:genetics / Q000648:ultrastructure*; D002473:Cell Wall / Q000648:ultrastructure; D003593:Cytoplasm; D035264:Flowers / Q000235:genetics / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D051479:Plant Infertility; D011058:Pollen / Q000235:genetics / Q000648:ultrastructure*