Biogenesis of Mitochondria in Imbibed Peanut Cotyledons: Influence of the Axis

Abstract

Development of mitochondrial activities (state 3 respiration, respiratory control ratio, ADP/O ratio) in peanut cotyledons occurs over the first 5 d from the start of imbibition. Mitochondria in cotyledons with the axis attached develop better than in those from which the axis has been removed. Initially, mitochondria are deficient in cytochrome c, but after 2 d from the start of imbibition this deficiency is overcome. Mitochondrial development in attached cotyledons, as measured by state 3 respiration, respiratory control ratio, ADP/O ratio, and succinate dehydrogenase and cytochrome oxidase activities, is severely impaired by cycloheximide. This indicates that de novo synthesis of proteins is necessary for mitochondria and their enzymes to develop, a situation which is in sharp contrast to the situation in pea cotyledons. Electron microscope studies also show that there is an increase in the numbers of mitochondria in peanut cotyledons with time after the start of imbibition. Two patterns of mitochondrial development exist in legumes: in imbibed peanut cotyledons respiratory activities increase due to biogenesis of mitochondria, whereas in pea cotyledons the increases are due to improvement of pre-existing organelles.