Structural diversity of the wheat nuclear gene waox1a encoding mitochondrial alternative oxidase, a single unique enzyme in the cyanide-resistant alternative pathway

Abstract

Alternative respiratory pathways other than the main cytochrome pathway are present in plant mitochondria, one of which is represented by a single unique enzyme alternative oxidase (AOX). Two genes encoding AOX proteins in common wheat have already been characterized (24). To further understand the structural diversity of the Aox genes in wheat, we screened the common wheat genome library for additional members of this small multigene family. Twelve Aox-related sequences were detected by Southern blot and restriction analyses and four of them were successfully subcloned and sequenced. All of the newly isolated sequences appear to be more closely related to the wheat gene Waox1a than Waox1c. Structural analysis showed that one clone was identical to Waox1a and three others appeared to be non-functional as they contained insertion/deletion mutations and/or frame-shift mutations leading to in-frame stop codons on different locations. In addition, one genomic clone highly homologous to the Waox1a cDNA sequence was identified. This cDNA-like sequence was also identified in the genomes of diploid, tetraploid and hexaploid wheat accessions. Although its origin remained unknown, our result indicated that it evolved before divergence of the ancestral wheat genomes. © 2005 Taylor and Francis Group, LLC.