Differences in kinetics of F₁-ATPases of cytoplasmic male sterile, maintainer and fertility restored lines of sorghum

Abstract

A comparative analysis of mitochondrial functions was carried out in the cytoplasmic male sterile A1 (milo) cytoplasm, its maintainer and the fertility restored lines. The study of temperature dependence (15-45° C) of the rates of uncoupled whole chain electron transport in the three lines did not reveal any differences between them at any of the temperatures studied. The partitioning of electrons between the cyanide-sensitive and the cyanide-insensitive respiratory pathways also did not show any differences between the three lines. However, differences in the kinetic properties of the isolated mitochondrial F₁-ATPases between the sterile and the fertility restored lines were clearly observed. The studies revealed that while a strong negative cooperativity between the subunits of the F₁-ATPases of the fertile maintainer and the fertility restored hybrid lines was observed, the F1-ATPase from the sterile line, in contrast, showed much reduced negative cooperativity. It is proposed that these differences in kinetic properties of the F₁-ATPase may play a role in the expression of the CMS trait at the time of anther formation.