Heteroplasmy in the T-urf13 mitochondrial gene of the Texas cytoplasm of maize

Abstract

In maize (Zea mays L.), the Texas (T) cytoplasm carries male sterility (cms-T) and susceptibility to host-specific fungal toxins and to the insecticide methomyl, traits of great interest both for basic research and plant breeding. These traits are apparently inseparable, and they are directly associated with the T-urf13 mitochondrial gene, which encodes a 13-kilodalton protein (URF13). Reversion to male fertility, associated with toxin/methomyl resistance, has been observed in progenies of cms-T somaclones regenerated from methomyl resistant calli. Diversity for PCR amplification of T-urf13 sequence and URF13 expression was observed within revertant progenies. Apparently, this diversity occurred among tissues within ear and tassel, and between ears and tassels of individual plants. The results demonstrate heteroplasmy in T-urf13 sequence persisting through several generations of T-cytoplasm mutants, that apparently consisted of deletions and sequence alterations. Furthermore, URF13 deficiency suggested that total or partial cytoplasmic reversions to male fertility in cms-T somaclones are caused by T-urf13 heteroplasmy