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Wheat Information
Service
Number 76: 70-72 (1993)
Structure
analysis of mitochondria genomes in interspecific hybrids related to
Aegilops triuncialis
Y. Ogihara, M. Furuya and T. Sasakuma
Kihara Institute for Biological Research, Yokohama City
University, Nakamura-cho 2-120-3, Yokohama 232, Japan
Mitochondria genome of angiosperm is known to show some
characteristic features such as; 1) plasticity of genome structure,
2) promiscuous DNA, and 3) RNA editing. In order to analyze
structural alterations of mitochondria genomes in interspecific
hybrids related to Aegilops triuncialis (CCUU as genome
formula), Restriction Fragment Length Polymorphism (RFLP) analysis of
mitochondrial DNAs in Ae. triuncialis complex was carried out.
Ae. triuncialis complex was used for the study, because
various combinations of interspecific hybrids (natural hybrids,
ancestral species, artificially synthetic strains and alloplasmic
lines) were obtained.
Total DNAs were isolated from the young seedlings of 20 strains of
Ae. triuncialis complex (Table1)
according to the CTAB method (Murray and Thompson 1980). These DNAs
were digested with Bam HI and Hind III, and
hybridized with twelve mitochondrial genes as probes
(Table
2) to carry out
RFLP analysis. RFLP analysis of total chloroplast DNAs from five
strains of Ae. triuncialis as well as common wheat was also
conducted.
Chloroplast DNAs of five strains were classified into three groups,
namely C type, U type and the third type (Murai and Tsunewaki 1986),
the two of which revealed the identical fragment pattern with those
of Ae. caudata (C type) and Ae. umbellulata (U),
respectively (Ogihara and Tsunewaki 1988). No ancestral strains
corresponding to the third type of Ae. triuncialis was found,
so far examined.
Based on the fragment patterns produced from Southern hybridization
in combination of twelve mitochondrial gene probes with two
restriction enzymes, namely 24 probe-enzyme combination, similarity
among eighteen strains was calculated. Using the similarity value, a
dendrogram showing genetic relationships among eighteen strains were
constructed according to the UPGMA (Nei 1975) as shown in
Fig.1.
Mitochondrial DNAs of
Ae. triuncialis were classified into three major groups,
namely C type, U type and the third type. The mitochondrial DNA of
the third type of Ae. triuncialis (#) was much closer to the C
type rather than the U type. These lines of evidence support the data
obtained from RFLP analysis of chloroplast DNAs. But intraspecific
variations were found in both mitochondria DNAs of C and U groups. It
is striking that mitochondrial DNA of Jones Fife was diversed from
other mitochondrial DNAs of B type (Fig.1),
although the fragment patterns of chloroplast DNA of Jones Fife was
identical to that of other common wheat. It is noteworthy that
mitochondrial genomes of interspecific hybrids were different from
those of original strains: Fragment patterns of trn1-trn2, S-trn1,
S-trn2, and J02 differed from those of cdt1. Simultaneously, those of
trn4-trn7, and trn8 were different from that of umb1. Cdt1 and umb1
were the cytoplasm donors of hybrid species of Ae. triuncialis
including synthetic strains and alloplasmic lines. This suggests
that mitochondrial DNAs were possibly changed during and/or after
interspecific hybridization. These lines of evidence indicate the
plasticity of mitochondria genome in wheat complex.
References
Murray HG and Thompson WF (1980) Rapid isolation of high
molecular weight plant DNA. Nucl Acid Res 8: 4321-4325.
Murai K and Tsunewaki K (1986) Molecular basis of genetic diversity
among cytoplasms of Triticum and Aegilops species.IV
CtDNA variation in Ae. triuncialis. Heredity 57: 335-339.
Nei M (1975) Molecular population genetics and evolution. North
Holland.
Ogihara Y and Tsunewaki K (1988) Diversity and evolution of
chloroplast DNA in Triticum and Aegilops as revealed by
restriction fragment analysis. Their Appl Genet 76: 321-332.
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