Annals of Botany 92: 309-316, 2003
© 2003 Annals of Botany Company
Variability of the 5S and 45S rDNA Sites in Passiflora L. Species with Distinct Base Chromosome Numbers
1 Embrapa Semi-Árido, C.P.23, 56302-970, Petrolina, Pernambuco, Brazil and 2 Department of Botany, CCB, Federal University of Pernambuco, Rua Nelson Chaves s/n, 50670-420, Recife, Pernambuco, Brazil
* For correspondence. Fax + 55 87 3862 1744, e-mail natoniel{at}cpatsa.embrapa.br
Received: 18 December 2002; ; Returned for revision: 12 March 2003. Accepted: 4 May 2003
Cytologically, the species of Passiflora with known chromosome number can be divided into four groups: (1) 2n = 12, 24, 36; (2) 2n = 24; (3) 2n = 18, 72; and (4) 2n = 20. The base chromosome number proposed for the genus is x = 6, with x = 9, x = 10 and x = 12 being considered secondary base numbers. In the present study, variability of 5S and 45S rDNA sites was investigated in 20 species of these four groups to check the reliability of this hypothesis. In the group with x = 6, five diploid species (2n = 12) exhibit two 5S rDNA sites and two (P. capsularis, P. morifolia and P. rubra) or four (P. misera 2x and P. tricuspis) 45S rDNA sites. The hexaploid cytotype of P. misera had 12 45S rDNA sites and six 5S rDNA. A tetraploid species, P. suberosa, had ten 45S rDNA sites and four 5S rDNA sites, both in the same chromosomes as the 45S rDNA sites. In the group with x = 9, P. actinia, P. amethystina, P. edmundoi, P. elegans, P. galbana, P. glandulosa and P. mucronata displayed six 45S rDNA sites, whereas P. alata, P. cincinnata, P. edulis f. flavicarpa, P. edulis var. roxo and P. laurifolia had four sites. In this group, all species were diploid (2n = 18) and had only two 5S rDNA sites. Passiflora foetida, the only species with 2n = 20, had six 45S rDNA sites and four 5S rDNA sites. The species with x = 12 (2n = 24), P. haematostigma and P. pentagona, showed four 45S rDNA sites and two 5S rDNA. In general, the number and location of 5S and 45S rDNA sites were consistent with the hypothesis of x = 6 as the probable ancestral genome for the genus, while the groups of species with x = 9, x = 10 and x = 12 were considered to be of tetraploid origin with descending dysploidy and gene silencing of some redundant gene sites, mainly those of 5S rDNA.
Key words: Passiflora, chromosome base number, FISH, rDNA, karyotype.
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  S. He, M. Huang, J. Huang, J. Li, Y. Hu, L. Zhang, C. Zhang, S.-z. Fei, and L. Li Dynamics of the Evolution of the Genus of Agrostis Revealed by GISH/FISH Crop Sci., October 22, 2009; 49(6): 2285 - 2290. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Q. CAI, D. ZHANG, Z.-L. LIU, and X.-R. WANG Chromosomal Localization of 5S and 18S rDNA in Five Species of Subgenus Strobus and their Implications for Genome Evolution of Pinus Ann. Bot., May 1, 2006; 97(5): 715 - 722. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. VAIO, P. SPERANZA, J. F. VALLS, M. GUERRA, and C. MAZZELLA Localization of the 5S and 45S rDNA Sites and cpDNA Sequence Analysis in Species of the Quadrifaria Group of Paspalum (Poaceae, Paniceae) Ann. Bot., August 1, 2005; 96(2): 191 - 200. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. P. LORENZ-LEMKE, V. C. MUSCHNER, S. L. BONATTO, A. C. CERVI, F. M. SALZANO, and L. B. FREITAS Phylogeographic Inferences Concerning Evolution of Brazilian Passiflora actinia and P. elegans (Passifloraceae) Based on ITS (nrDNA) Variation Ann. Bot., April 1, 2005; 95(5): 799 - 806. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. B. MARCON, I. C. L. BARROS, and M. GUERRA Variation in Chromosome Numbers, CMA Bands and 45S rDNA Sites in Species of Selaginella (Pteridophyta) Ann. Bot., January 2, 2005; 95(2): 271 - 276. [Abstract] [Full Text] [PDF]
|
|