The B Chromosome of Corn

Carlson, Wayne R.

doi:10.1146/annurev.ge.12.120178.000253

Cited by 75 publications

(52 citation statements)

References 38 publications

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“…naturally occurring supernumerary chromosomes (10)(11)(12). The B chromosome is basically inert, and its presence at low number does not affect the phenotype of plants.…”

Section: Resultsmentioning

confidence: 99%

“…The B chromosome of maize is basically inert, without any known active genes (10)(11)(12). However, it is not known whether the lack of gene activity on B chromosomes is caused by the absence of genes or by suppression of transcription because of its heterochromatic nature.…”

Section: Resultsmentioning

confidence: 99%

“…As its accumulation mechanism, the maize B chromosome undergoes nondisjunction during pollen mitosis and preferential fertilization of the egg cell by the sperm with B chromosomes (10). This property requires the long arm of the chromosome to be present in the same cell as the centromere (10) and would be eliminated by truncation.…”

Section: Gus Expression Is Absent In Kernel (B) But Present In Both Ementioning

confidence: 99%

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Construction and behavior of engineered minichromosomes in maize

Han

Gao

et al. 2007

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

142

138

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Engineered minichromosomes were constructed in maize by modifying natural A and supernumerary B chromosomes. By using telomere-mediated chromosomal truncation, it was demonstrated that such an approach is feasible for the generation of minichromosomes of normal A chromosomes by selection of spontaneous polyploid events that compensate for the deficiencies produced. B chromosomes are readily fractionated by biolistic transformation of truncating plasmids. Foreign genes were faithfully expressed from integrations into normal B chromosomes and from truncated miniB chromosomes. Site-specific recombination between the terminal transgene on a miniA chromosome and a terminal site on a normal chromosome was demonstrated. It was also found that the miniA chromosome did not pair with its progenitor chromosomes during meiosis, indicating a useful property for such constructs. The miniB chromosomes are faithfully transmitted from one generation to the next but can be changed in dosage in the presence of normal B chromosomes. This approach for construction of engineered chromosomes can be easily extended to other plant species because it does not rely on cloned centromere sequences, which are species-specific. These platforms will provide avenues for studies on plant chromosome structure and function and for future developments in biotechnology and agriculture.artificial chromosomes ͉ FISH ͉ genetic engineering ͉ telomere truncation A rtificial chromosomes involving de novo centromere formation on an independently assembled unit and engineered minichromosomes produced by telomere truncation provide striking advantages over traditional methods of gene transformation in yeast and mammalian cells (1-5). The development of such chromosomes in plants would provide these advantages for many applications in basic studies, biotechnology, and agriculture. These chromosomes could be used as independent platforms for foreign gene expression without random integration into the normal chromosomes. Further additions of unlimited amounts of DNA could be added to these platforms in a sequential manner via different site-specific recombination cassettes. Genes introduced in this way would be present in a defined context and thus could be expressed at a more predictable level than through random integration (6). Hence, additional genes, multigene complexes, or even whole metabolic pathways could potentially be added to a genotype. Moreover, engineered or artificial chromosomes could be easily introduced or removed from a genotype by genetic crosses and would facilitate introgression of transgenes to different genetic backgrounds.To extend engineered chromosome technology to plants, we developed a method of telomere-mediated chromosomal truncation in maize by Agrobacterium-mediated transformation of constructs with multiple copies of the telomere sequence (7). Here, we report the use of this technology to produce minichromosome platforms by truncating both normal A and supernumerary B maize chromosomes and at the same time introducing site-spe...

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“…naturally occurring supernumerary chromosomes (10)(11)(12). The B chromosome is basically inert, and its presence at low number does not affect the phenotype of plants.…”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Gus Expression Is Absent In Kernel (B) But Present In Both Ementioning

confidence: 99%

See 1 more Smart Citation

Construction and behavior of engineered minichromosomes in maize

Han

Gao

et al. 2007

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

142

138

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“…These polymorphisms are mediated by three main cytological processes: (i) B nondisjunction at the second pollen grain mitosis, which produces sperm nuclei with different B number (Roman, 1947;Carlson, 1978;Carlson and Chou, 1981); (ii) preferential fertilisation by the sperm nucleus carrying the Bs after the non-disjunction process (Roman, 1948;Carlson, 1969); (iii) the suppression of meiotic loss when the Bs are unpaired (Carlson and Roseman, 1992).…”

Section: Introductionmentioning

confidence: 99%

“…The genetic control of the nondisjunction process is owing to a region in the B chromosome itself, which was determined using deletions of B chromatin in B-A translocation lines (Lin, 1978(Lin, , 1979Carlson, 1978;Carlson and Chou, 1981). Variation in nondisjunction frequency was reported by Rusche et al (1997) using a molecular probe to detect the presence, location and frequency of B chromosomes in interphase nuclei of pollen grains in the TB-10 L18 translocation line.…”

Section: Introductionmentioning

confidence: 99%

One gene determines maize B chromosome accumulation by preferential fertilisation; another gene(s) determines their meiotic loss

et al. 2003

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Genotypes of high (H m ) and low (L m ) male B transmission rate (B-TR) were obtained. B-TR segregation in the F2 is reported, showing that the H m and L m lines differ in a single locus we call mBt (male B transmission), controlling B preferential fertilisation in maize. The egg cells control which one of the sperm nuclei is going to fertilise them, mBt h egg cells being preferentially fertilised by the sperm nucleus carrying the supernumerary B chromosomes (Bs). It is hypothesised that the mBt gene is involved in the normal fertilisation of maize but the parasitic Bs take advantage of the mBt h allele to increase their own transmission. Selection was also carried out when the Bs were transmitted on the female side (H f and L f lines). The F1 hybrids show that the gene(s) that we call fBt (female B transmission), controlling female B-TR, is located on the A chromosomes acting at diploid level, the fBt l allele(s) for low transmission being dominant. This allele causes the loss of Bs at meiosis, which is shown using a specific B molecular probe to determine B presence/absence in microspores of both lines and hybrids. Maize Bs are a nice example of intragenome conflict, because the mBt and fBt loci are a polymorphic system of attack and defence between A and B chromosomes.

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Chromosome structure rearrangements and genome relationship in Maydeae

Sharma¹,

Sarma²

1988

Feddes Repert

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The B Chromosome of Corn

Cited by 75 publications

References 38 publications

Construction and behavior of engineered minichromosomes in maize

Construction and behavior of engineered minichromosomes in maize

One gene determines maize B chromosome accumulation by preferential fertilisation; another gene(s) determines their meiotic loss

Chromosome structure rearrangements and genome relationship in Maydeae

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