The isolation of mitochondria and mitochondrial DNA. Plant Molecular Biology. Elsevier; 1986. pp. 437-53. [DOI: 10.1016/0076-6879(86)18091-8]

A male sterility-associated mitochondrial protein in wild beets causes pollen disruption in transgenic plants

In higher plants, male reproductive (pollen) development is known to be disrupted in a class of mitochondrial mutants termed cytoplasmic male sterility (CMS) mutants. Despite the increase in knowledge regarding CMS-encoding genes and their expression, definitive evidence that CMS-associated proteins actually cause pollen disruption is not yet available in most cases. Here we compare the translation products of mitochondria between the normal fertile cytoplasm and the male-sterile I-12CMS(3) cytoplasm derived from wild beets. The results show a unique 12 kDa polypeptide that is present in the I-12CMS(3) mitochondria but is not detectable among the translation products of normal mitochondria. We also found that a mitochondrial open reading frame (named orf129) was uniquely transcribed in I-12CMS(3) and is large enough to encode the novel 12 kDa polypeptide. Antibodies against a GST-ORF129 fusion protein were raised to establish that this 12 kDa polypeptide is the product of orf129. ORF129 was shown to accumulate in flower mitochondria as well as in root and leaf mitochondria. As for the CMS-associated protein (PCF protein) in petunia, ORF129 is primarily present in the matrix and is loosely associated with the inner mitochondrial membrane. The orf129 sequence was fused to a mitochondrial targeting pre-sequence, placed under the control of the Arabidopsis apetala3 promoter, and introduced into the tobacco nuclear genome. Transgenic expression of ORF129 resulted in male sterility, which provides clear supporting evidence that ORF129 is responsible for the male-sterile phenotype in sugar beet with wild beet cytoplasm.

The 5'-leader sequence of sugar beet mitochondrial atp6 encodes a novel polypeptide that is characteristic of Owen cytoplasmic male sterility

Cytoplasmic male sterility (CMS) is a mitochondrially encoded trait, which is characterized by a failure of plants to produce viable pollen. We have investigated the protein profile of mitochondria from sugar beet plants with normal (fertile) or CMS cytoplasm, and observed that a 35-kDa polypeptide is expressed in Owen CMS plants but not in normal plants. The variant 35-kDa polypeptide was found in CMS mitochondria placed in five different nuclear backgrounds. Interestingly, this polypeptide proved to be antigenically related to a 387-codon ORF (preSatp6) that is fused in-frame with the downstream atp6. The presequence extension of the atp6 ORF is commonly found in higher plants, but whether or not it is normally expressed has hitherto remained unclear. Our study is thus the first to demonstrate that the atp6 presequence is actually translated in mitochondria. We also observed that preSATP6 is a mitochondrial membrane protein that assembles into a homogeneous 200-kDa protein complex. In organello translation experiments in the presence of protease inhibitors showed a reduction in the abundance of mature preSATP6 with time, suggesting that the mature preSATP6 may be derived by proteolytic processing of a translation product of the preSatp6/Satp6 ORF.

An influence of stress protein CSP 310 and antiserum against this protein on lipid peroxidation in cereal mitochondria

It is determined that an addition of an anti-CSP 310 antiserum to isolated winter wheat and maize mitochondria caused more significant increasing of spontaneous lipid peroxidation than the addition of stress protein CSP 310. It is shown that, at function of different mitochondrial respiratory chain complexes, the lipid peroxidation in winter wheat and maize mitochondria take place with different intensities. Under the functioning of mitochondrial respiratory chain complex IV, the maximum output of lipid peroxidation products, dienic conjugates is detected. The presence of antiserum against CSP 310 in incubation media induces lipid peroxidation more than the presence of CSP 310 in mitochondria isolated from stressed plants under these conditions. Based on data obtained, it is possible to conclude that in vivo endogenous CSP 310, during a cold stress, has an antioxidant activity the same as other known uncoupling proteins.

Plant stress-related uncoupling protein CSP 310 caused lipid peroxidation in winter wheat mitochondria under chilling stress

The effect of CSP 310 on lipid peroxidation in winter wheat mitochondria was studied by the measurement of primary lipid peroxidation products - dienic conjugates. It was found that some concentrations of CSP 310 caused lipid peroxidation in isolated winter wheat mitochondria in all systems investigated at different concentrations during chilling stress.

Cytoplasmic diversity in leaf beet cultivars as revealed by mitochondrial DNA analysis

Mitochondrial (mt) DNA restriction fragment length polymorphisms are convenient markers for identifying cytoplasmic variation among plant cultivars. In an attempt to detect new cytoplasmic genotypes useful for sugarbeet breeding, we have compared the hybridization patterns of mtDNA from three groups of cultivated beets, viz. leaf beet, garden beet, and fodder beet. Utilized as probes were the two sugarbeet mtDNA clones that were capable of distinguishing normal fertile and different sources of male-sterile cytoplasms from one another. The analysis allowed the identification of four chondriome types among 14 leaf beet cultivars examined. Two out of the four chondriome types were found to be different from the previously described fertile or male-sterile chondriome type. Our results thus indicate that leaf beet cultivars and landraces make up the primary cytoplasmic gene pool of the sugarbeet.

Involvement of two different urf-s related mitochondrial sequences in the molecular evolution of the CMS-specific S-Pcf locus in petunia

In petunia, a mitochondrial (mt) locus, S-Pcf, has been found to be strongly associated with cytoplasmic male sterility (CMS). The S-Pcf locus consists of three open reading frames (ORF) that are co-transcribed. The first ORF, Pcf, contains parts of the atp9 and coxII genes and an unidentified reading frame, urf-s. The second and third ORFs contain NADH dehydrogenase subunit 3 (nad3) and ribosomal protein S12 (rps12) sequences, respectively. The nad3 and rps12 sequences included in the S-Pcf locus are identical to the corresponding sequences on the mt genome of fertile petunia. In both CMS and fertile petunia, only a single copy of nad3 and rps12 had been detected on the physical map of the main mt genome. The origin of the urf-s sequence and the molecular events leading to the formation of the chimeric S-Pcf locus are not known. This paper presents evidence indicating that two different mt sequences, related to urf-s and found in fertile petunia lines (orf-h and Rf-1), might have been involved in the molecular evolution of the S-Pcf locus. Southern analysis of mtDNA derived from both fertile and sterile petunia plants suggests that one of these urf-s related sequences (showing 100% homology to urf-s and termed orf-h) is located on a sublimon. An additional, low-homology urf-s related sequence (Rf-1) is shown to be located on the main mt genome 5' to the nad3 gene. It is, thus, suggested that the sequence of events leading to the generation of the S-Pcf locus might have involved introduction of the orf-h sequence, via homologous recombination, into the main mt genome 5' to nad3 at the region where the Rf-1 sequence is located.

Mitochondrial gene variation and phylogenetic relationships in the genus Beta

Restriction fragment length polymorphisms (RFLPs) for three mitochondrial genes, coxI, coxII and atpA, were used to determine mitochondrial (mt) DNA diversity in 21 accessions of the genus Beta representing wild and cultivated species. On the basis of distribution of the RFLP patterns these Beta genotypes were assigned into six distinct chondriome groups. A high degree of heterogeneity was found to exist between the mitochondrial genomes of the sugarbeet cultivar and the wild species of Procumbentes section. The polymorphic fragments from wild Beta species were cloned and subjected to fine mapping. We found that most of the RFLPs are due to sequence rearrangements rather than point mutations. Our data also suggest that the close linkage between coxII and coxI is taxonomically localized to an evolutionary lineage that led to Vulgares and Corollinae species but not to Procumbentes species. This linkage is most likely to have arisen via the mutation(s) that inserted the DNA segment containing coxI downstream of coxII in the common ancestor of Vulgares and Corollinae species. The results are discussed with regard to the taxonomic and phylogenetic relationships of the Beta species.

Expression of the CMS-associated urfS sequence in transgenic petunia and tobacco

The expression of a 25 kDa protein, encoded by the fused mitochondrial pcf gene, is associated with cytoplasmic male sterility (CMS) in petunia. To investigate the role of the 25 kDa protein in CMS we have transformed petunia and tobacco plants with constructs expressing a portion of the urfS sequence of the pcf cDNA which encodes the 25 kDa protein. The urfS sequence was fused with two different mitochondrial targeting sequences. The chimeric gene coding region was placed under the control of the CaMV 35S promoter or a tapetum-specific promoter. Expression of the PCF protein was obtained in mitochondria of transgenic petunia and tobacco plants, yet fertility of the plants was not affected. Analysis of the location of the urfS-encoded protein revealed that it fractionates primarily into the soluble fraction in the transgenic plants whereas the genuine 25 kDa protein is found primarily in the soluble fraction but also in the membrane portion of immature buds from CMS petunia plants. Fertile transgenic plants were obtained which expressed the 25 kDa protein in the tapetal layer of post-meiotic anthers, while CMS plants express the endogenous 25 kDa protein in both the tapetal layer and sporogenous tissue of pre-meiotic anthers.

Mitochondrial genome of the dimorphic zygomycete Mucor racemosus

Mitochondria were isolated from the dimorphic zygomycete Mucor racemosus by differential centrifugation. DNA from the organelles was purified by cesium chloride-ethidium bromide isopycnic centrifugation. Examination of the mitochondrial DNA by electron microscopy revealed a circular chromosome approximately 63.8 kbp in circumference. The chromosome was digested with restriction endonucleases and the resulting DNA fragments were separated by agarose-gel electrophoresis. Electophoretic mobilities and stoichiometry of the fragments indicated a mixed population of mtDNA molecules each with a size of about 63.4 kbp. Physical maps were constructed from analyses of fragments generated in single and double restriction digests and from the hybridization of fragments to probes for the large and small mitochondrial rRNA genes from Saccharomyces cerevisiae. The Mucor mitochondrial chromosome was found to exist in the form of two flip-flop isomers with inverted repeat sequences encoding both rRNA genes.

Multiple trans-splicing events are required to produce a mature nad1 transcript in a plant mitochondrion

The mitochondrial gene encoding NADH dehydrogenase subunit 1 (nad1) in Petunia hybrida is split into five exons, a, b, c, d, and e. With the use of a complete restriction map of the 443-kb Petunia mitochondrial genome, we have cloned these exons and mapped their location. Exon a is located 130 kb away from and in the opposite orientation from exons b and c. Exon d maps 95 kb away and in the opposite orientation from exons b and c. Exons d and e are separated by 190 kb. By performing the polymerase chain reaction on Petunia cDNAs, we have shown that transcripts from these five exons are joined via a series of cis- and trans-splicing events to create a mature nad1 transcript. In addition, we have found 23 C----U RNA edit sites in Petunia nad1. RNA editing changes 19 of the amino acids predicted by the genomic sequence.

Transcription of the Petunia mitochondrial CMS-associated Pcf locus in male sterile and fertility-restored lines

Transcripts of the Petunia mitochondrial cytoplasmic male sterility (CMS)-associated S-Pcf locus, which consists of three co-transcribed genes (pcf, NADH dehydrogenase subunit 3, and ribosomal protein S12), have been characterized in reproductive tissues of CMS and fertility restored (Rf) Petunia lines by nuclease protection experiments and by RNA blot hybridization. Three 5' transcript termini have been previously described. Two 3' transcript termini and an additional S-Pcf locus transcript have now been identified. The relative abundance of the three 5' transcript termini is influenced by the presence of the nuclear Rf gene. A decrease in the abundance of the -121 5' transcript terminus relative to the -266 and -522 termini is consistently seen in Petunia lines which are restored to fertility by the Rf gene, compared to CMS Petunia lines. An additional transcript with a 5' terminus within the urf-s region of pcf is much more abundant in immature bud and anther tissue than in leaf or suspension cells. The total abundance of pcf transcripts varies greatly between plants of different nuclear backgrounds which lack the nuclear Rf allele, indicating that other nuclear genes also influence expression of the S-Pcf locus.

Splicing of the Petunia cytochrome oxidase subunit II intron

A comparative analysis of the plant intron-containing mitochondrial cytochrome oxidase subunit II (coxII) genes provides an indication that four conserved sequence motifs, present in exon 1 (intron-binding sequences; IBS), and complementary motifs (exon-binding sequences; EBS), present in domain I of the group II intron, may be involved in splicing of the intron. Two of these potential IBS motifs (IBS1 and IBS2) have been previously discussed. Two further potential IBS motifs (IBSa and IBSb), which occur twice within exon 1, could be involved in specification of the 5' splice site and of a 5' cryptic splice site. Nuclease-protection experiments and DNA sequence analysis of a spliced coxII cDNA have confirmed the predicted positions of the petunia coxII 5' and 3' splice sites. Evidence for the occurrence of splicing in vivo at the putative 5' cryptic splice site in petunia is provided by the detection of a nuclease-protected fragment corresponding to the size which is predicted if splicing at the proposed cryptic splice site occurs. The existence and location of a cryptic splice site, upstream of the normal coxII 5' splice site, is consistent with the proposed derivation of the cytoplasmic male sterility (CMS)-associated pcf gene from an abnormally spliced coxII transcript (Pruitt and Hanson 1989).

Comparison of the organization of the mitochondrial genome in tomato somatic hybrids and cybrids

The organization of the mitochondrial genome in somatic hybrids and cybrids regenerated following fusion of protoplasts from cultivated tomato, Lycopersicon esculentum, and the wild species, L. Pennellii, was compared to assess the role of the nuclear genotype on the inheritance of organellar genomes. No organellar-encoded traits were required for the recorvery of either somatic hybrids or cybrids. The organization of the mitochondrial genome was characterized using Southern hybridization of restriction digestions of total DNA isolated from ten cybrids and ten somatic hybrids. A bank of cosmid clones carrying tomato mitochondrial DNA was used as probes, as well as a putative repeated sequence from L. pennellii mitchondrial DNA. The seven cosmids used to characterize the mitochondrial genomes are predicted to encompass at least 60% of the genome. The frequency of nonparental organizations of the mitochondrial genome was highest with a probe derived from a putative repeat element from the L. pennellii mitochondrial DNA. There was no difference in the average frequency of rearranged mitochondrial sequences in somatic hybrids (12%) versus cybrids (10%), although there were individual cybrids with a very high frequency of novel fragments (30%). The frequency of tomato-specific mtDNA sequences was higher in cybrids (25%) versus somatic hybrids (12%), suggesting a nuclear-cytoplasmic interaction on the inheritance of tomato mitochondrial sequences.

A termination codon is created by RNA editing in the petunia atp9 transcript

Analysis of the cDNA of the atp9-1 gene transcript from petunia mitochondria has revealed that ten C residues of the gene sequence are edited into U in the mRNA. Seven of these edits result in amino acid changes and one introduces a stop codon before the end of the open reading frame predicted from the gene sequence. The resulting protein is better conserved when compared to the same protein in other organisms. Comparison of the edited petunia sequence with other plant mitochondrial atp9 gene sequences idicates variation in the number and positions of edits required to obtain the same amino acids in ATP9 polypeptides of higher plants.

Cytochrome oxidase subunit II sequences in Petunia mitochondria: two intron-containing genes and an intron-less pseudogene associated with cytoplasmic male sterility

The mitochondrial genome of Petunia hybrida contains two transcribed cytochrome oxidase subunit II (coxII) genes. The coding region of both genes is split by a 1.3 kb group II intron. Unlike coxII-1, which is similar to other sequenced plant coxII genes, the coxII-2 coding region is extended by 48 codons. The cytoplasmic male sterile (CMS) Petunia contains one coxII gene similar in structure and transcript pattern to the coxII-1 gene found in the fertile genome. Comparison of the sequenced coxII genes from the fertile mitochondrial genome with the coxII sequences present in the CMS-associated pcf gene from the CMS genome (Young and Hanson 1987) suggests that pcf is a processed pseudogene. A model for the generation of pcf is presented.

Interspecific somatic hybrid plants between eggplant (Solanum melongena) and Solanum torvum

Mesophyll protoplasts of eggplant (cv Black Beauty) and of Solanum torvum (both 2n=2x=24) were fused using a modification of the Menczel and Wolfe PEG/DMSO procedure. Protoplasts post-fusion were plated at 1 × 10(5)/ml in modified KM medium, which inhibited division of S. torvum protoplasts. One week prior to shoot regeneration, ten individual calluses had a unique light-green background and were verified as cell hybrids by the presence of the dimer isozyme patterns for phosphoglucoisomerase (PGI) and glutamate oxaloacetate transaminase (GOT). Hybridity was also confirmed at the plant stage by DNA-DNA hybridization to a pea 45S ribosomal RNA gene probe. The ten somatic hybrid plants were established in the greenhouse and exhibited intermediate morphological characteristics such as leaf size and shape, flower size, shape, color and plant stature. Their chromosome number ranged from 46-48 (expected 2n=4x=48) and pollen viability was 5%-70%. In vitro shoots taken from the ten hybrid plants exhibited resistance to a verticillium wilt extract. Total DNA from the ten hybrids was restricted and hybridized with a 5.9 kb Oenothera chloroplast cytochrome f gene probe, a 2.4 kb EcoRI clone encoding mitochondrial cytochrome oxidase subunit II from maize and a 22.1 kb Sal I mitochondrial clone from Nicotiana sylvestris. Southern blot hybridization patterns showed that eight of ten somatic hybrids contained the eggplant cpDNA, while two plants contained the cpDNA hybridization patterns of both parents. The mtDNA analysis revealed the presence of novel bands, loss of some specific parental bands and mixture of specific bands from both parents in the restriction hybridization profiles of the hybrids.

A new protocol for isolation of mitochondrial DNA from cotton seedlings

A procedure to isolate mtDNA from cotton seedlings G. hirsutum and G. barbadense has been developed. The new protocol allows for the isolation of cotton mtDNA of high purity, yield and digestibility by restriction endonucleases. The success of the protocol is based on critical adjustments in the ionic strength of the homogenizing medium and washing buffer, the speed of grinding during homogenization, and the methods used for lysis of the mitochondria.