A Biochemical Study of Cytoplasmic Male-sterility of Corn: Alteration Cytochrome Oxidase and Malate Dehydrogenase Activities during Pollen Development

Abstract

Cytoplasmic male-sterility of corn is related to altered functions of mitochondria. To substantiate this hypothesis, we studied the activities of two mitochondrial enzymes, cytochrome oxidase (cyt. oxidase) and malate dehydrogenase (MDH), in anthers and flag leaves of normal and male-sterile lines. Corn cultivar WF9 with normal (N) cytoplasm and its isogenic lines with male-sterile (MS) T-. S- and C-cytoplasms were used for experiments. Developing tassels in flag leaves were sampled from the plants. A portion of the tassel was fixed in acetic alcohol for microscopic examination of the stage of pollen development. A known weight of anthers was collected from another portion of the tassel. It was then homogenized in a buffered medium containing sucrose, and centrifuged to yield three fractions; "precipitate fraction", "mltochondnal fraction" and "supernatant fraction". Cyt. oxidase and MDH, activities of each fraction were assayed, and activity values per gram of fresh sample were calculated.