Nondisjunction and isochromosome formation in the B chromosome of maize

Carlson, Wayne R.

doi:10.1007/bf00321067

Cited by 36 publications

(26 citation statements)

References 14 publications

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“…but is "healed" in the embryo, which when grown and analyzed cytologically will reveal the nature of the new chromosomes formed (13,17). This type of screen was used to assemble a large collection of misdivisions to examine the structural features of the B centromere (18).…”

Section: Significancementioning

confidence: 99%

“…The B centromere of B-9 can undergo misdivision during meiosis, producing many derivatives (14). The first misdivision derivative was a pseudoisochromosome, and subsequently, many telocentric chromosomes and isochromosomes were derived by additional misdivisions (13,17). Misdivision events can be recognized in crosses of TB-9Sb onto a tester via a fusion-breakage cycle recognized by the behavior of the C1 color marker on the B-9 chromosome.…”

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confidence: 99%

“…Previous work sought misdivision derivatives of the B chromosome centromere using a translocation between the supernumerary chromosome and the short arm of chromosome 9 (9S) to reduce the size of the centromere for functional studies (13)(14)(15). B chromosomes are extra chromosomes that have been found in many plants, animals, and fungi.…”

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confidence: 99%

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Sequential de novo centromere formation and inactivation on a chromosomal fragment in maize

Liu

Pang

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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The ability of centromeres to alternate between active and inactive states indicates significant epigenetic aspects controlling centromere assembly and function. In maize (Zea mays), misdivision of the B chromosome centromere on a translocation with the short arm of chromosome 9 (TB-9Sb) can produce many variants with varying centromere sizes and centromeric DNA sequences. In such derivatives of TB-9Sb, we found a de novo centromere on chromosome derivative 3-3, which has no canonical centromeric repeat sequences. This centromere is derived from a 288-kb region on the short arm of chromosome 9, and is 19 megabases (Mb) removed from the translocation breakpoint of chromosome 9 in TB-9Sb. The functional B centromere in progenitor telo2-2 is deleted from derivative 3-3, but some B-repeat sequences remain. The de novo centromere of derivative 3-3 becomes inactive in three further derivatives with new centromeres being formed elsewhere on each chromosome. Our results suggest that de novo centromere initiation is quite common and can persist on chromosomal fragments without a canonical centromere. However, we hypothesize that when de novo centromeres are initiated in opposition to a larger normal centromere, they are cleared from the chromosome by inactivation, thus maintaining karyotype integrity.centromere misdivision | epigenetics | de novo centromere | centromere inactivation T he centromere is an important chromosomal region responsible for correct chromosome segregation during cell division. Centromeres are found in the primary constriction region on the chromosome, upon which the kinetochore complex assembles to produce a platform for spindle binding (1). Centromere function is conserved among different species, and several epigenetic markers of active centromeres have been found, including a histone H3 variant referred to as CENH3 in plants (2, 3) or CENP-A in animals (4-6) and phosphorylation of histone H2A at Thr133 in plants (7). Correct loading of CENH3 to the centromere region is a key component of kinetochore assembly (8). Centromeric DNA sequences have experienced rapid evolution (9, 10), and arrangements of DNA sequence in centromere regions differ in species and even in different chromosomes of an individual organism (11). Myriad repeat sequences exist in the centromeres of higher plants. In maize (Zea mays), there are two major types of centromere specific DNA sequences: the simple satellite repeat sequence CentC (12) and centromeric retrotransposon of maize (CRM) (3). Many epigenetic features have been identified in centromeric regions, including DNA methylation levels, histone variants, histone modifications, and RNA components (11). Both epigenetic elements and DNA sequences take part in centromere formation and maintenance, but it is still unknown how genetic and epigenetic factors work together in this process.The centromere is one of the most complex regions on the chromosome, and complete DNA sequencing through the centromeric region is difficult to obtain due to their highly repetitive nature...

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Section: Significancementioning

confidence: 99%

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confidence: 99%

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Sequential de novo centromere formation and inactivation on a chromosomal fragment in maize

Liu

Pang

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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“…One such translocation has figured into studies of the B centromere over many years and is referred to as TB-9Sb (Carlson, 1970). It is a reciprocal exchange between the short arm of chromosome 9 (9S) and the B chromosome such that genetic markers on 9S are linked to the B centromere.…”

Section: Introductionmentioning

confidence: 99%

“…It is a reciprocal exchange between the short arm of chromosome 9 (9S) and the B chromosome such that genetic markers on 9S are linked to the B centromere. Carlson (1970) discovered a derivative of TB-9Sb that had suffered a misdivision of the centromere resulting in a chromosome with two copies of 9S. Subsequent studies have continued to recover sequential misdivision derivatives so that now a large collection has been recovered Birchler, 1996, 1998).…”

Section: Introductionmentioning

confidence: 99%

Reactivation of an Inactive Centromere Reveals Epigenetic and Structural Components for Centromere Specification in Maize

2009

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Stable maize (Zea mays) chromosomes were recovered from an unstable dicentric containing large and small versions of the B chromosome centromere. In the stable chromosome, the smaller centromere had become inactivated. This inactive centromere can be inherited from one generation to the next attached to the active version and loses all known cytological and molecular properties of active centromeres. When separated from the active centromere by intrachromosomal recombination, the inactive centromere can be reactivated. The reactivated centromere regains the molecular attributes of activity in anaphase I of meiosis. When two copies of the dicentric chromosome with one active and one inactive centromere are present, homologous chromosome pairing reduces the frequency of intrachromosomal recombination and thus decreases, but does not eliminate, the reactivation of inactive centromeres. These findings indicate an epigenetic component to centromere specification in that centromere inactivation can be directed by joining two centromeres in opposition. These findings also indicate a structural aspect to centromere specification revealed by the gain of activity at the site of the previously inactive sequences.

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Misdivision analysis of centromere structure in maize.

1996

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The size and organization of a representative plant centromere from the supernumerary B chromosome were determined using a repeated sequence specific to the centric region. Several derivatives of the B chromosome that suffered from misdivision of the centromere were analyzed for the content and organization of their B repeat. In all these derivatives, major rearrangements were detected. Some misdivisions produced a significant reduction in size of the B‐specific cluster. These results demonstrate that the B repeat is part of the functional centromere, that it is spread throughout its length, and that plant centromeres are composed of repeat units that can be significantly changed in copy number without a change in function.

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Nondisjunction and isochromosome formation in the B chromosome of maize

Cited by 36 publications

References 14 publications

Sequential de novo centromere formation and inactivation on a chromosomal fragment in maize

Sequential de novo centromere formation and inactivation on a chromosomal fragment in maize

Reactivation of an Inactive Centromere Reveals Epigenetic and Structural Components for Centromere Specification in Maize

Misdivision analysis of centromere structure in maize.

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