Karyotype Description and Comparative Chromosomal Mapping of 5S rDNA in 21 species

5S rDNA is essential component of all cell types. A survey was conducted to study the 5S rDNA site number, position, and origin of signal pattern diversity in 64 plants using fluorescence in situ hybridization. The species used for this experiment were chosen due to the discovery of karyotype rearrangement, and for species checked in which 5S rDNA has not yet been explored. The chromosome number was 14-160, while the chromosome length was 0.63-6.88 m, with 37 plants (58%) had small chromosome (<3 m). The chromosome numbers of three species and 5S rDNA loci of 19 species have been reported for the first time. 5S rDNA was varied and abundant in signal site number (2-18), position (e.g., interstitial, distal, and proximal position, occasionally, outside chromosome), and even as intense (e.g., strong, weak, and slight). Our results exposed modifiability in the number and location of 5S rDNA in 33 plants and demonstrated an extensive stable number and location of 5S rDNA in 31 plants. The potential origin of signal pattern diversity was probably caused by chromosome rearrangement (e.g., deletion, duplication, inversion, translocation), polyploidization, self-incompatibility, and chromosome satellites. These data characterized the variability of 5S rDNA within the karyotypes of the 64 plants that exhibited massive chromosomal rearrangements and provided anchor points for genetic physical maps. These data prove the utility of the 5S rDNA oligonucleotide as a chromosome marker in identifying plant chromosomes. This method provides a basis for developing similar applications for cytogenetic analysis in other species. Article SummaryA survey was exploited to study 5S rDNA signal pattern diversity in 64 plants by FISH. The chromosome number of three species and 5S rDNA loci of 19 species have been reported by the first time. 5S rDNA was really rather various and abundant in signal site number (2-18), position (interstitial, distal, proximal position, occasionally, outside chromosome), even as the intense (strong, week, slight). These data prove the utility of 5S rDNA oligonucleotide as chromosome marker in identifying plant chromosomes.