ISSN 1022-7954, Russian Journal of Genetics, 2006, Vol. 42, No. 3, pp. 279–285. © Pleiades Publishing, Inc., 2006.
Original Russian Text © I.S. Mazheika, O.L. Kolomiets, Yu.T. Dyakov, Yu.F. Bogdanov, 2006, published in Genetika, 2006, Vol. 42, No. 3, pp. 361–368.
Chromosome condensation, synapsis of homolo-
gous chromosomes, and meiotic recombination are
most important and correlated events of meiotic
prophase I. Many genes directly involved in homolo-
gous recombination exert a great impact on the interac-
tion between homologs in meiosis, formation of chro-
mosome axial elements (AEs), and synaptonemal com-
plexes (SCs) . This interaction is conﬁrmed by
analysis of mutations in meiotic recombination genes.
For example, the SPO11 gene of the
produces a Top-2-like protein, which induces two-
strand DNA breaks and meiotic recombination at the
early meiotic prophase. However, null mutants for
SPO11 show disrupted formation of AEs and, particu-
larly, SCs. Normal SCs occur only in 1% of meiocytes.
This may be related to the fact that the meiotic ZIP2 and
ZIP3 genes, involved in the beginning of the assem-
blage of the central SC element from the Zip1 protein,
are Spo11-dependent [2–4].
Another example is the enzyme complex of yeast
recombination, coded by genes MRE11/RAD50/XRS2. It
performs exonuclease-mediated release of the 3'-end
at double-strand DNA breaks. It is likely that the
Mre11/Rad50/Xrs2 complex, together with the
Rad51/Rad55/Rad57 complex and Dmc1, is involved
in the invasion of the 3'-end into the homologous DNA
to form a heteroduplex intermediate. Mutations for the
RAD11 (MRE11) gene in
cause partial loss
of ability of homologous chromosomes not only to syn-
apt but even to pair each other [5–11].
In turn, mutations in the genes for SC structural pro-
teins can affect meiotic recombination. It is known that
with disruption of forma-
tion of the central SC element also show disrupted
crossover interference. In the
mutant, which forms
neither AEs nor, correspondingly, SC, crossover fre-
quency is 4 times lower than normal [7, 12].
Electrophoretic analysis of isozyme and DNA pat-
terns revealed a reduced frequency of meiotic recombi-
nation in white button mushroom
[13–16]. Recombination suppression is likely to be
among the components determining its life cycle fea-
tures. Apart from white button mushroom, recombina-
tion suppression was found in other fungal species with
similar life cycles .
The life cycle of white button mushroom is as fol-
lows: the majority of mushroom basidia, formed on the
surface of fruit-body gills, have two spores. During
meiosis in the basidia, the speciﬁc orientation of the
division spindles in anaphase II results in nonrandom
distribution of four postmeiotic nuclei among two
spores. As a result, most spores have two nonsib nuclei
with different states of the MAT locus. Such spores ger-
Abnormal Meiosis in Bisporic Strains
of White Button Mushroom
I. S. Mazheika
, O. L. Kolomiets
, Yu. T. Dyakov
, and Yu. F. Bogdanov
Department of Mycology and Algology, Moscow State University, Moscow, 119899 Russia;
e-mail: email@example.com, firstname.lastname@example.org
Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow, 119991 Russia;
e-mail: email@example.com, firstname.lastname@example.org
Received June 9, 2005
—A formerly developed method of microspreading of mushroom basidial nuclei was applied to study
meiotic prophase I in bisporic white button mushroom (
) strains. Meiotic recombination and
assemblage of axial structures (axial elements and synaptonemal complexes) of chromosomes in meiotic
prophase I are interrelated. It is known that the frequency of meiotic recombination is reduced in the bisporic
variety. We showed that formation of axial structures of meiotic chromosomes in bisporic strains
of this mushroom was disrupted. The anomalous phenotypes in spread prophase nuclei are diverse. In leptotene
and early zygotene, many nuclei contain abnormal, often short, and, as a rule, few chromosomal axial elements.
The abnormalities in the formation of synaptonemal complexes at the zygotene–diplotene stage are of the same
kind and even more pronounced. We discovered an important feature of meiosis in
fruit-body morphogenesis. Meiosis starting in basidia (meiocytes) of young closed fruit bodies is accompanied
by disruption of chromatin condensation in prophase I and, probably, is arrested. After partial veil breakage, the
course of meiosis normalizes. Preparations with clearly observable chromosomal axial structures can be
obtained only at this stage of fruit-body development.