THE EXPRESSION OF ALTERNATIVE OXIDASE AND ALTERNATIVE RESPIRATORY CAPACITY IN CYTOPLASMIC MALE-STERILE COMMON BEAN

The alternative respiratory pathway is present in all plant species in vestigated to date. Yet, the role of the alternative pathway is not cl ear. Some evidence suggests an important role in pollen development. W e undertook this study to investigate the expression of alternative ox idase, in comparison with expression of a component of cytochrome oxid ase, during pollen formation in common bean (Phaseolus vulgaris L.). E xpression was evaluated immunohistochemically. In addition, we compare d both the alternative oxidase capacity in young seedling tissues and alternative oxidase expression in developing flower buds of isonuclear cytoplasmic male sterile and male fertile bean lines. We observed no evidence of an association between the abnormal pollen development of CMS bean and changes in alternative oxidase expression or capacity. We did observe a tissue- and stage-specific pattern of expression of alt ernative oxidase, differing from the expression pattern of cytochrome oxidase subunit II, during anther development in normal bean lines. Al though no association was evident between the cytoplasmic male sterili ty phenotype and differential expression of alternative oxidase, the r egulated pattern of alternative oxidase expression in developing anthe rs does suggest that the alternative pathway may play a role in microg ametogenesis and microsporogenesis.