Journal
CYTOGENETIC AND GENOME RESEARCH
Volume 132, Issue 1-2, Pages 105-112Publisher
KARGER
DOI: 10.1159/000320705
Keywords
B chromosomes; Nierembergia; Nucleolar activity; Nucleolar dominance; Solanaceae
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Funding
- Secretaria de Ciencia y Tecnologia, Universidad Nacional de Cordoba, Argentina (SECYT-UNC)
- Argentine Research Council (CONICET)
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B chromosomes are additional dispensable chromosomes that may be present in some individuals, populations, or species, which have probably arisen from the A chromosomes but follow their own evolutionary pathway. Supposedly, B chromosomes do not contain major genes except for ribosomal DNA (rDNA) sequences that have been mapped on the supernumerary chromosomes of many plants and animals. This paper is a new report of B chromosome occurrence in plants. B chromosomes with nucleolar organizing regions (NORs) were found in a diploid sample of Nierembergia aristata D. Don (sub nom. N. stricta Miers) (2n = 2x = 16). This is an extreme case in which B chromosomes possess not only strong nucleolar activity, as revealed by conventional staining methods, AgNOR and fluorescence banding, and fluorescent in situ hybridization (FISH), but also show nucleolar competition with the A chromosomes. The observed phenomenon could be analogous to the nucleolar dominance or 'differential amphiplasty' phenomenon that occurs in interspecific hybrids. Copyright (C) 2010 S. Karger AG, Basel
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