Molecular cytogenetics of forest trees

Abstract

The economic and ecological importance of forest trees, as well as their unique biological features, has recently raised the level of interest in studies on their genomes, including sequencing of the entire poplar genome. However, cytogenetic studies have not moved in parallel with developments in genomics. This is especially true for hardwood species characterized by small genomes and relatively high numbers of small chromosomes. Molecular cytogenetic studies have mainly been focused on coniferous species, owing to the larger size of their chromosomes, and have been applied exclusively for chromosome identification and comparative karyotyping in an attempt to understand genome evolution and phylogenetic relationships. In this context, rRNA genes physical mapped by FISH reveal particularly useful chromosomal landmarks with variable distribution patterns between species. Here we present a contribution of DNA markers used for chromosome analysis, which already allowed a deeper characterization and understanding of the processes underlying genome diversity of forest trees. The use of advanced cytogenetic techniques and other potential important methods for genome analysis of forest trees is also discussed.

Cytogenetic Analysis of <i>Populus trichocarpa</i> – Ribosomal DNA, Telomere Repeat Sequence, and Marker-selected BACs

“…We observed that the 5S rDNA FISH signal in P. trichocarpa is much reduced compared to either of the 18S-28S rDNA signals, apparently because the 5S rDNA locus contains fewer repetitive units than either of the 18S-28S rDNA loci. Similar results were also reported for P. nigra [Ribeiro et al, 2008].…”

Identification of peanut (Arachis hypogaea) chromosomes using a fluorescence in situ hybridization system reveals multiple hybridization events during tetraploid peanut formation

“…FISH‐based karyotyping relies on chromosome markers, which are independent of genetic diversity, and may complement genetic mapping in studies of chromosome organization and evolution. Chromosome identification systems employing FISH have been used to construct karyotypes or cytogenetic maps in rice ( Oryza sativa ), Sorghum bicolor , maize ( Zea mays ), Antirrhinum majus , poplar ( Populus alba ), common bean ( Phaseolus vulgaris ), soybean ( Glycine max ), melon ( Cucumis melo ) and Brassica napus (Cheng et al ., ; Islam‐Faridi et al ., ; Kato et al ., ; Zhang et al ., ; Ribeiro et al ., ; Pedrosa‐Harand et al ., ; Findley et al ., ; Fonseca et al ., ; Liu et al ., ; Pires & Xiong, ). Large genomic clones, such as bacterial artificial chromosomes (BACs), provide reliable landmarks with which to discriminate individual chromosomes in many crops such as rice (Cheng et al ., ) and Brassica (Pires & Xiong, ).…”

Plant rDNA database: update and new features

“…Sequences of ribosomal RNA genes and their spacers have been used profusely in an array of molecular phylogenetic (12, 13) and other approaches to plant evolution (14–16). Number, position and rDNA organization can also be used for, or at least complement comparative, evolutionary and systematic approaches (17–19), assuming that the karyotypes of closely related species are likely to be more similar than those of distant species (20, 21).…”