Nuclear-mitochondrial interactions in cytoplasmic male-sterile sorghum

Abstract

Variation in mitochondrial genome organization and expression between male fertile and sterile nuclear-cytoplasmic combinations of sorghum has been examined. Cytoplasmic genotypes were classified into eleven groups on the basis of restriction endonuclease digestion of mitochondrial DNA (mtDNA) and five groups on the basis of mitochondrial translation products. These cytoplasms were further characterized by hybridization of specific gene probes to Southern blots of EcoRI digested mtDNA, and identification of the fragment location of four mitochondrial genes. Variation was observed in the genomic location and copy number of the F1 ATPase α-subunit gene, as well as the genomic location and gene product of the cytochrome c oxidase subunit I gene. The effect of nuclear genotype on mitochondrial genome organization, expression and the presence of two linear plasmid-like mtDNA molecules was examined. Our results indicate that nuclear-mitochondrial interactions are required for regulation of mitochondrial gene expression. When a cytoplasm is transferred from its natural to a foreign nuclear background some changes in the products of in organello mitochondrial protein synthesis occur. In a number of cytoplasmic genotypes these changes correlate with the expression of cytoplasmic male sterile phenotype, suggesting a possible molecular basis for this mutation.

Mitochondrial DNA diversity in wild and cultivated sorghum

“…This suggests that there is little genetic differentiation between cropped sorghum and the wild progenitors. However, greater differentiation of male sterile cytoplasmic lines using restricted mtDNA versus cpDNA was observed by Pring et al (1982) and Bailey-Serres et al (1986). For Doebley (1992), the greater differentiation would be the result of the higher rate of evolution of mtDNA compared with cpDNA.…”

Organ-specific reduction in the abundance of a mitochondrial protein accompanies fertility restoration in cytoplasmic male-sterile radish

“…Nucleusdependent changes in mitochondrial transcript [10, 27,36,40,47,51], and protein patterns [1,7,17,52] have also been reported for a number of systems, many of which have been associated with fertility restoration. In addition, changes in mitochondrial protein levels have recently been observed in developing petunia anthers [ 5 ].…”

Characterization of radish mitochondrial atpA: influence of nuclear background on transcription of atpA-associated sequences and relationship with male sterility

“…In addition, nuclear effects on the translation of several mitochondrial proteins in sorghum [ 1] and TURF-13 in the CMS-T cytoplasm of maize [9] have been observed. The primary effect of the maize nuclear RF1 gene appears to be post-transcriptional, acting as an RNA processing enzyme or a transcriptional or translational factor [ 10,16].…”