Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 2/27/2008
Publication Date: N/A
Citation: N/A Interpretive Summary: N/A
Technical Abstract: Nuclear gene products are required for the expression of mitochondrial genes and elaboration of functional mitochondrial protein complexes. To better understand the roles of these nuclear genes, we exploited the mitochondrial encoded S-type of cytoplasmic male sterility (CMS-S) and developed a novel collection of nuclear mutations affecting mitochondrial functions in maize. These mutations gametophytically restore fertility function to the pollen of CMS-S plants. Although the restorer mutations rescue CMS-S pollen, many are homozygous lethal for maize kernel development and might, therefore, disrupt essential mitochondrial functions. for our nine molecularly characterized CMS-S restorers, genetic complementation testing indicates allelism between only a spontaneous rfl2 mutant and one recovered form a transposon tagging population. We have profiled the transcripts and protein products of mitochondrial genes in developmentally staged pollen from those CMS-S restorer lines and an isogenic MO17 line having normal cytoplasm with no restorer genes. The profiles revealed that five restorer mutations conditioned global loss of mitochondrial gene products through post-transcriptional mechanisms. These mutants must therefore control mitochondrial protein accumulation via other post-transcriptional processes. We further tested this mechanism by examining RNA editing, a post-transcriptional feature of plant mitochondrial gene expression. The editing pattern of the maize mitochondrial atp6 gene was first determined by sequence analysis of atp6 RT-PCR products from microspores of non-restorer carrying normal and CMS-S cytoplasm isogenic lines. A high frequency of RNA editing caused codon changes, as well as the generation of several new restriction enzyme recognition sites. Restriction enzyme analysis of the atp6 RT-PCR products demonstrated that RNA editing generated the three sequencing predicted cleaved amplified polymorphism (CAPs)sites in the developing pollen of all our CMS-S restorer.