Carbon monoxide sensitivity of cytochrome c oxidase in male sterile seedlings of sorghum

Abstract

In order to study the possible role of mitochondrial and nuclear genes in the regulation of redox condition of cytochrome a 3 during steady-state respiration, a large number of cytoplasmic male sterile (CMS) lines of sorghum, their maintainers and hybrids were examined for carbon monoxide (CO) sensitivity. Differences in the redox state of cytochrome a 3 were monitored by using the in vivo aerobic assay of nitrate reductase after one min exposure to CO. CMS lines obtained from A 1, A 2, A 3 and A 4 cytoplasms as well as their maintainers, BT × −398, 365B and 42B were found to be sensitive to CO, indicating that cytochrome a 3 was in a considerably reduced state during steady-state respiration. A number of other indigenous CMS lines derived from Maldandi and other sources as well as their respective maintainers did not, however, react with CO. Restorers of fertility, CS-3541 and SPV-475, responded to CO. Hybrids obtained from these restorers, when crossed with CO-insensitive CMS lines, 2219A and 296A, also readily responded to the gas. Similarly CMS 365A derived from CO-resistant CMS 2219A was CO-sensitive because the maintainer 365B was CO-sensitive. Conversely CMS RSB-18A inherited CO-insensitivity from its male parent, RSB-18B; although the maternal parent CMS 2077A was CO-responsive. These results indicated that nuclear genes, contributed by the male parent, influence the redox state of cytochrome a 3 during steady-state respiration.