A mitochondrial DNA sequence is associated with abnormal pollen development in cytoplasmic male sterile bean plants.

Abstract

Cytoplasmic male sterility (CMS) in common bean is associated with the presence of a 3-kb unique mitochondrial sequence designated pvs. The pvs sequence encodes at least two open reading frames (297 and 720 bp in length) with portions derived from the chloroplast genome. Fertility restoration by the nuclear restorer gene Fr results in the loss of this transcriptionally active unique region. We examined the effect of CMS (pvs present) and fertility restoration by Fr @vs absent) on the pattern of pollen development in bean. In the CMS line, pollen aborted in-the tetrad stage late in microgametogenesis. Microspores maintained cytoplasmic connections throughout pollen development, indicating aberrant or incomplete cytokinesis. Pollen-specific events associated with pollen abortion and fertility restoration imply that a gametophytic factor or event may be involved in CMS. In situ hybridization experiments suggested that significant reduction or complete loss of the mitochondrial sterility-associated sequence occurred in fertile pollen of F2 populations segregating for fertility. These observations support a model of fertility restoration by the loss of a mitochondrial DNA sequence prior to or during microsporogenesis/gametogenesis.

Stoichiometric Shifts in the Common Bean Mitochondrial Genome Leading to Male Sterility and Spontaneous Reversion to Fertility

“…(D) Samples were digested with EcoRI and hybridized with a PCR-amplified pvs sequence; the band indicated by an arrowhead represents the mitochondrial fragment encompassing pvs. The upper, more intensely hybridizing band represents a chloroplast fragment that hybridizes by virtue of a small region of chloroplast tRNA Ala intron homology contained within the pvs region (Chase and Ortega, 1992;Johns et al, 1992). All mitochondrial DNA fragments present in the CMS-Sprite genome were detected in the genome of fertile progenitor POP.…”

Plant Mitochondrial Recombination Surveillance Requires Unusual RecA and MutS Homologs

“…Previous experiments to track the developmental timing of substoichiometric shifting (Johns et al, 1992;S.A. Mackenzie, unpublished data) have suggested that nuclear influence on mitochondrial genome configuration may be most pronounced during or immediately preceding flowering.…”

Transcript processing internal to a mitochondrial open reading frame is correlated with fertility restoration in male‐sterile sorghum

“…Internal sequences of sorghum off25, urf209, are represented internal to a cms-specific off, orf265 (Tang et aL, 1996), and a truncated atplwith unique 5' sequences is associated with cms in tobacco (Bergman et aL, 1996). Other open reading frames associated with cms can be derived from sequences not normally translated, such as maize T-urf13 (Dewey et aL, 1986), or be of unknown origin such as Brassica orf138 (Bonhomme et al, 1992;Krishnasamy and Makaroff, 1993) and Phaseolus orf239 (Chase and Ortega, 1992;Johns et al, 1992). Although several of the cmsassociated genes may consequently share some similarity at amino termini, to date little if any similarity in primary structure is evident for the remainder of the open reading frames; that is, each example appears to be species-or cytoplasm-specific.…”