scholarly journals The supernumerary B chromosome of maize: drive and genomic conflict

Open Biology ◽  
2021 ◽  
Vol 11 (11) ◽  
Author(s):  
James A. Birchler ◽  
Hua Yang
Keyword(s):  
Centromeric Region ◽  
B Chromosome ◽  
Supernumerary Chromosome ◽  
Divergence Times ◽  
Sperm Cells ◽  
Double Fertilization ◽  
Pollen Mitosis ◽  
Evolutionary Time ◽  
Genomic Conflict ◽  
Preferential Fertilization

The supernumerary B chromosome of maize is dispensable, containing no vital genes, and thus is variable in number and presence in lines of maize. In order to be maintained in populations, it has a drive mechanism consisting of nondisjunction at the pollen mitosis that produces the two sperm cells, and then the sperm with the two B chromosomes has a preference for fertilizing the egg as opposed to the central cell in the process of double fertilization. The sequence of the B chromosome coupled with B chromosomal aberrations has localized features involved with nondisjunction and preferential fertilization, which are present at the centromeric region. The predicted genes from the sequence have paralogues dispersed across all A chromosomes and have widely different divergence times suggesting that they have transposed to the B chromosome over evolutionary time followed by degradation or have been co-opted for the selfish functions of the supernumerary chromosome.

Locating a site on the maize B chromosome that controls preferential fertilization

Genome ◽  
2007 ◽  
Vol 50 (6) ◽  
pp. 578-587 ◽  
Author(s):  
Wayne R. Carlson
Keyword(s):  
B Chromosome ◽  
B Chromosomes ◽  
Chromosome 9 ◽  
Chromosome Deletion ◽  
Pollen Mitosis ◽  
Preferential Fertilization ◽  
Second Pollen Mitosis ◽  
A Site ◽  
Derivatives Of

In maize, the B chromosome can undergo nondisjunction at the second pollen mitosis, producing sperm with two B chromosomes and sperm with zero B chromosomes. Preferential fertilization is the ability of the sperm carrying two B chromosomes to transmit more frequently to the embryo of a kernel than the sperm lacking the B chromosome. A translocation involving the B chromosome and chromosome 9, TB-9Sb, has been used to study preferential fertilization. The B-9 chromosome has the same properties of nondisjunction and preferential fertilization as the standard B chromosome. Deletion derivatives of B-9, which lack the centric heterochromatin and possibly some adjacent euchromatin, were tested for their ability to induce preferential fertilization. They were found to lack the capacity for preferential fertilization.

scholarly journals B chromosome dynamics in Prochilodus costatus (Teleostei, Characiformes) and comparisons with supernumerary chromosome system in other Prochilodus species

2017 ◽  
Vol 11 (2) ◽  
pp. 393-403
Author(s):  
Silvana Melo ◽  
Ricardo Utsunomia ◽  
Manolo Penitente ◽  
Patrícia Elda Sobrinho-Scudeler ◽  
Fábio Porto-Foresti ◽  
...  
Keyword(s):  
B Chromosome ◽  
Supernumerary Chromosome ◽  
Chromosome Dynamics

scholarly journals B CHROMOSOME NONDISJUNCTION IN CORN: CONTROL BY FACTORS NEAR THE CENTROMERE

Genetics ◽  
1981 ◽  
Vol 97 (2) ◽  
pp. 379-389
Author(s):  
Wayne R Carlson ◽  
Tau-San Chou
Keyword(s):  
B Chromosome ◽  
B Chromosomes ◽  
Translocation Chromosome ◽  
Pollen Mitosis ◽  
Second Pollen Mitosis ◽  
Chromosome Nondisjunction

ABSTRACT B chromosomes of corn are stable at all mitotic and meiotic divisions of the plant except the second pollen mitosis. In the latter division, B chromosomes undego mitotic nondisjunction at rates as high as 98%. Studies by several workers on B-A translocation chromosomes have provided evidence for the existence of four factors on the B chromosome that control nondisjunction and are separable from the centromere. Two of these factors, referred to here as factors 3 and 4, flank the B chromosome centromere. Factor 3 is the centromere-adjacent heterochromatin in the long arm of the B chromosome; factor 4 is located in the minute short arm. Evidence is presented here supporting the existence of factors 3 and 4. Deficiencies that include each factor were identified following centromeric misdivision events, with breaks at or near the centromere of a B-translocation chromosome. B chromosomes lacking factors 3 or 4 show much less nondisjunction than do chromosomes containing them. The possible function of factor 4 in nondisjuntion is also discussed.

scholarly journals Diversification dynamics of total-, stem-, and crown-groups are compatible with molecular clock estimates of divergence times

2021 ◽  
Vol 7 (24) ◽  
pp. eabf2257
Author(s):  
Alan J. S. Beavan ◽  
Davide Pisani ◽  
Philip C. J. Donoghue
Keyword(s):  
Time Scales ◽  
Molecular Clock ◽  
Fossil Record ◽  
Divergence Times ◽  
Evolutionary Time ◽  
Crown Group ◽  
Total Group ◽  
Fossil Evidence ◽  
Evolutionary Radiations ◽  
Birth Death

Molecular evolutionary time scales are expected to predate the fossil evidence, but, particularly for major evolutionary radiations, they can imply extremely protracted stem lineages predating the origin of living clades, leading to claims of systematic overestimation of divergence times. We use macroevolutionary birth-death models to describe the range of total-group and crown-group ages expected under constant rates of speciation and extinction. We extend current predictions on origination times for crown- and total-groups, and extinction of stem-groups, demonstrating that there is broad variance in these predictions. Under constant rates of speciation and extinction, we show that the distribution of expected arthropod total-group ages is consistent with molecular clock estimates. The fossil record cannot be read literally, and our results preclude attempts to interpret the antiquity of clades based on the co-occurrence of stem- and crown-representatives.

Unstable inheritance of maize B-type chromosomes that lack centric heterochromatin

Genome ◽  
2006 ◽  
Vol 49 (5) ◽  
pp. 420-431 ◽  
Author(s):  
Wayne R Carlson
Keyword(s):  
B Chromosome ◽  
Chromosome 9 ◽  
Pollen Mitosis ◽  
Genetic Studies ◽  
Telocentric Chromosome ◽  
Deletion Derivative ◽  
Translocation Heterozygote ◽  
Second Pollen Mitosis

The B chromosome of maize undergoes frequent non-disjunction at the second pollen mitosis. In B–A translocations, the B–A chromosome retains the capacity for non-disjunction. We have collected deletion-derivative TB-9Sb stocks. One derivative, the "type 1 telocentric", has a B–9 chromosome that lacks centric heterochromatin. It produces few recessive (non-disjunctional) phenotypes in pollen parent testcrosses of the translocation heterozygote, 9 9–B telo B–9. The finding helped demonstrate the role of centric heterochromatin in non-disjunction. An isochromo some derivative of the type 1 telocentric was also recovered. It was tested in the 9–B 9–B iso B–9 constitution. This is equivalent to 9 9–B telo B–9 in terms of chromosome 9 dosage. Surprisingly, crosses with the isochromosome gave significant levels of recessive phenotypes. In addition, high levels of variegated phenotypes were found. Recently, a circumstance was found that makes inheritance of the type 1 telocentric chromosome somewhat similar to that of the isochromosome. Crosses with hypoploid 9–B 9–B telo B–9 plants showed significant levels of recessive and variegated phenotypes. These crosses were investigated to help explain the source(s) of the phenotypes. Cytological and genetic studies were performed. Centric misdivision was found to account for the variegated phenotypes. A mixture of conventional B non-disjunction and centric misdivision produced the recessive phenotypes. The significance of conventional non-disjunction in the absence of centric heterochromatin is discussed.Key words: cytogenetics, B chromosome, centromere, maize.

Female gametophyte-controlled pollen tube guidance

2010 ◽  
Vol 38 (2) ◽  
pp. 627-630 ◽  
Author(s):  
Mihaela-Luiza Márton ◽  
Thomas Dresselhaus
Keyword(s):  
Pollen Tube ◽  
Female Gametophyte ◽  
Cell Communication ◽  
Flowering Plants ◽  
Sperm Cells ◽  
Double Fertilization ◽  
Pollen Tube Guidance ◽  
Communication Events ◽  
Extensive Cell

During the evolution of flowering plants, their sperm cells have lost mobility and are transported from the stigma to the female gametophyte via the pollen tube to achieve double fertilization. Pollen tube growth and guidance is largely governed by the maternal sporophytic tissues of the stigma, style and ovule. However, the last phase of the pollen tube path is under female gametophyte control and is expected to require extensive cell–cell communication events between both gametophytes. Until recently, little was known about the molecules produced by the female gametophyte that are involved in this process. In the present paper, we review the most recent development in this field and focus on the role of secreted candidate signalling ligands.

Changes in NOR activity pattern in the presence of supernumerary heterochromatin in the grasshopper Eyprepocnemis plorans

Genome ◽  
1995 ◽  
Vol 38 (1) ◽  
pp. 68-74 ◽  
Author(s):  
M. D. López-León ◽  
J. Cabrero ◽  
J. P. M. Camacho
Keyword(s):  
Activity Patterns ◽  
Organizer Region ◽  
Nucleolus Organizer Region ◽  
Adult Life ◽  
B Chromosome ◽  
Nucleolus Organizer ◽  
Supernumerary Chromosome ◽  
Eyprepocnemis Plorans ◽  
X Chromosomes ◽  
Active Nors

Nucleolus organizer region (NOR) activity was analysed in four types of males of the grasshopper Eyprepocnemis plorans, possessing two kinds of supernumerary heterochromatin: a B chromosome and a supernumerary chromosome segment proximally located on the smallest autosome (S11). In males lacking extra heterochromatin, the four active NORs located on the S9, S10, S11, and X chromosomes showed independent activity patterns, but several kinds of dependence appeared in the presence of supernumerary heterochromatin. Furthermore, temporal changes in NOR activity were observed during the first 2 weeks of adult life in standard males but not in males carrying supernumerary heterochromatin. It is suggested that all these effects are related to the DNA content of both types of extra heterochromatin.Key words: NOR, supernumerary heterochromatin, grasshopper, Eyprepocnemis plorans.

Population cytogenetics of Chorthippus vagans. II. Reduced meiotic transmission but increased fertilization by males possessing a supernumerary chromosome

Genome ◽  
1987 ◽  
Vol 29 (2) ◽  
pp. 285-291 ◽  
Author(s):  
Josefa Cabrero ◽  
Juan Pedro M. Camacho
Keyword(s):  
Sexual Selection ◽  
Mass Culture ◽  
Low Frequency ◽  
Phenotypic Selection ◽  
B Chromosome ◽  
Supernumerary Chromosome ◽  
Relative Fitness ◽  
C Banding ◽  
Meiotic Transmission ◽  
The One

A submetacentric B chromosome was present at a low frequency (ca. 4%) in a natural population of the grasshopper Chorthippus vagans. Its heterochromatic nature is shown by its positive heteropycnosis during first meiotic prophase and by its response to C-banding. As its C-banding pattern and the meiotic autopairing of its two arms both demonstrate, it appears to have been derived from a metacentric iso-B chromosome by means of a pericentric inversion. The frequencies of equational division of the B univalents and the formation of abnormal gametes were significantly different between the 2 one B males found. A causal relationship is demonstrated between the equational division of the B at anaphase I and the formation of spermatid micronuclei, which can be assumed to contain B chromosomes that are being eliminated. Such B elimination was higher in male no. 2 than in male no. 37. The estimated B-transmission frequency was 0.28 for male no. 2 and 0.46 for male no. 37. The presence in the same population of polymorphisms for the M4 and M7 autosomes made it possible to determine the specific parents for four egg pods containing the B chromosome produced in a mass culture using wild-caught individuals. From this we calculate the actual transmission of the B by the one B males to be 0.27 for male no. 2 and 0.44 for male no. 37, which agrees with their respective estimated transmission frequencies. The relative fitness of zero B and one B males was calculated in terms of their viability and fertility components. While viability was lower for one B individuals, their fertility was much higher than that of zero B males. Indeed, sexual selection in favour of one B males was sufficiently high to counteract both the reduced transmission of the B by one B males and the phenotypic selection against one B zygotes. Key words: Chorthippus, meiotic drag, supernumerary chromosome, B chromosome, sexual selection.

scholarly journals Is maize B chromosome preferential fertilization controlled by a single gene?

Heredity ◽  
2001 ◽  
Vol 86 (6) ◽  
pp. 743-748 ◽  
Author(s):  
A Mauricio Chiavarino ◽  
Mónica González-Sánchez ◽  
Lidia Poggio ◽  
María J Puertas ◽  
Marcela Rosato ◽  
...  
Keyword(s):  
Single Gene ◽  
B Chromosome ◽  
Preferential Fertilization

scholarly journals De novo centromere formation on chromosome fragments with an inactive centromere in maize (Zea mays)

2021 ◽  
Author(s):  
Ryan N. Douglas ◽  
Hua Yang ◽  
Bing Zhang ◽  
Chen Chen ◽  
Fangpu Han ◽  
...  
Keyword(s):  
De Novo ◽  
Low Frequency ◽  
B Chromosome ◽  
Chromosome 9 ◽  
Centromere Region ◽  
Pollen Mitosis ◽  
Accumulation Mechanism ◽  
Chromosome Fragments ◽  
Breakpoint Determination ◽  
Second Pollen Mitosis

AbstractThe B chromosome of maize undergoes nondisjunction at the second pollen mitosis as part of its accumulation mechanism. Previous work identified 9-Bic-1 (9-B inactivated centromere-1), which comprises an epigenetically silenced B chromosome centromere that was translocated to the short arm of chromosome 9(9S). This chromosome is stable in isolation, but when normal B chromosomes are added to the genotype, it will attempt to undergo nondisjunction during the second pollen mitosis and usually fractures the chromosome in 9S. These broken chromosomes allow a test of whether the inactive centromere is reactivated or whether a de novo centromere is formed elsewhere on the chromosome to allow recovery of fragments. Breakpoint determination on the B chromosome and chromosome 9 showed that mini chromosome B1104 has the same breakpoint as 9-Bic-1 in the B centromere region and includes a portion of 9S. CENH3 binding was found on the B centromere region and on 9S, suggesting both centromere reactivation and de novo centromere formation. Another mini chromosome, B496, showed evidence of rearrangement, but it also only showed evidence for a de novo centromere. Other mini chromosome fragments recovered were directly derived from the B chromosome with breakpoints concentrated near the centromeric knob region, which suggests that the B chromosome is broken at a low frequency due to the failure of the sister chromatids to separate at the second pollen mitosis. Our results indicate that both reactivation and de novo centromere formation could occur on fragments derived from the progenitor possessing an inactive centromere.

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