Mitochondrial DNA variation in maize plants regenerated during tissue culture selection

Abstract

Plants resistant to Helminthosporium maydis race T were obtained following selection for H. maydis pathotoxin resistance in tissue cultures of susceptible, Texas male-sterile (T) cytoplasm maize. The selected lines transmitted H. maydis resistance to their sexual progeny as an extranuclear trait. Of 167 resistant, regenerated plants, 97 were male fertile and 70 were classified male sterile for reasons that included abnormal plant, tassel, anther or pollen development. No progeny were obtained from these male-sterile, resistant plants. Male fertility and resistance to the Phyllosticta maydis pathotoxin that specifically affects T cytoplasm maize were co-transmitted with H. maydis resistance to progeny of male-fertile, resistant plants. These three traits previously were associated only with the normal (N) male-fertile cytoplasm condition in maize. Three generations of progeny testing provided no indication that the cytoplasmic association of male sterility and toxin susceptibility had been broken by this selection and regeneration procedure. Restriction endonuclease analysis of mitochondrial DNA (mtDNA) revealed that three selected, resistant lines had distinct mtDNA organization that distinguished them from each other, from T and from N cytoplasm maize. Restriction patterns of the selected resistant lines were similar to those from T cytoplasm mtDNA; these patterns had not been observed in any previous analyses of various sources of T cytoplasm. The mtDNA analyses indicated that the male-fertile, toxin-resistant lines did not originate from selection of N mitochondrial genomes coexisting previously with T genomes in the T cytoplasm line used for selection.

Patterns of mitochondrial DNA instability in Brassica campestris cultured cells

“…Third, both in our evolutionary and in vitro studies we noted that most of the structural alterations of the Brassica mitochondrial genome occur at specific sites via recombination across short repeated elements. Although a number of studies have already demonstrated an increased plasticity of plant mtDNA in response to tissue culture manipulations [ 17,7,39,41,50,21,4] it is still uncertain as to whether these 'culture-induced' alterations occur systematically in all higher-plant species or whether they reflect particular culture conditions such as culture age [34] or the in vitro technique employed [23]. A study of in vitro mtDNA alterations of maize [7] has also shown that the occurrence of specific types of rearrangements (i.e.…”

Interactions of Mitochondrial and Nuclear Genes That Affect Male Gametophyte Development

“…The maize urf13 gene is located upstream of a conserved mitochondrial gene termed orf221, which encodes a membranebound protein (Prioli et al, 1993), now identified as ATP4 (Heazlewood et al, 2003). Critical confirmation that urf13 causes pollen disruption came from characterizing mitochondrial genomes in fertile revertants that arose from cell culture (Gengenbach et al, 1981), in which were detected deletions that disrupted the urf13 gene (Umbeck and Gengenbach, 1983;Abbott and Fauron, 1986;Rottmann et al, 1987). A particularly important revertant was described by Wise et al (1987), who observed that a 5-bp insertion in urf13, causing a frame shift and a premature stop codon, was sufficient to confer fertility.…”

The Genetics, Pathology, and Molecular Biology of T-Cytoplasm Male Sterility in Maize

“…Concurrently, a map-based approach took advantage of the male-fertile, toxin-insensitive mutants described above. In 19 of 20 such mutants, a 6.7-kb XhoI mitochondrial DNA restriction fragment was altered due to a partial deletion (Gengenbach et al, 1981;Kemble et al, 1982;Umbeck and Gengenbach, 1983;Fauron et al, 1987). The remaining male-fertile mutant, T-4, retained the 6.7-kb XhoI fragment.…”