Cellular energy levels and their effect on male cell abortion in cytoplasmically male sterile lines of Petunia hybrida

Summary Using an HPLC method it has proved possible to follow the levels of adenine and pyridine nucleotides in the anthers of normal and cytoplasmically male sterile (CMS) lines of Petunia hybrida. Well before the appearance of any structural differences, anthers of CMS plants begin to show lower ATP/ADP ratios. In anthers, as in other non-photosynthetic plant tissues, there is a strong correlation between the ATP/ADP ratio and levels of NADPH and, when NADPH was assayed in fertile and CMS anthers, very dramatic differences were discovered. In male fertile plants, the NADPH/NADP ratio differs strikingly between somatic and reproductive tissues and reaches a peak in anthers at the early prophase of meiosis. The ratio in male sterile anthers remains largely unchanged from that normally seen in somatic tissues over this period. A cytochemical localisation technique revealed that, at the stage of development in question, the major reserves of anther NADPH are held within the tapetal cells and that levels within CMS tapeta are strikingly lower than those of normal plants. These findings are discussed in the perspective of theories proposed to explain the operation of CMS, and also in terms of the now conclusive evidence that the genetical basis of CMS lies in changes in the organisation of the mitochondrial genome.