Karyotype Analysis of Three Juniperus Species using Fluorescence in situ Hybridization (FISH) with Two Ribosomal RNA Genes

Abstract

Summary Detailed karyotypes and the fluorescence in situ hybridization (FISH) using 5S and 18S rDNA probes was applied to 3 species of the genus Juniperus. The number of chromosomes of J. chinensis var. sargentii and J. lutchuensis was 2nϭ22, except for J. chinensis var. procumbens (2nϭ44). Chromosomal sites of 5S rDNA were on one pair of the short arm of the median-centromeric chromosome and 18S rDNA were at the secondary constriction. No minor signals of 5S and 18S rDNA probes were detected in the Juniperus chromosomes. We developed karyotypes using McFISH with 5S and 18S rDNA, and reported the first time chromosome makers of the family Cupressaceae.

Molecular cytogenetic studies in western Mediterranean Juniperus (Cupressaceae): a constant model of GC-rich chromosomal regions and rDNA loci with evidences for paleopolyploidy

“…The other representative of the Cupressaceae studied (Cryptomeria) presents four bands (two loci), suggesting that this family is characterised, within the gymnosperms, by a low number of rDNA loci. The location in a SC agrees with that of the other Juniperus taxa investigated (Nagano et al 2007), and other studies on gymnosperms (Table 2) procumbens (Nagano et al 2007). This fact can be interpreted as accounting for the age of polyploidy in J. thurifera: after the polyploidisation event and the stabilisation of the doubled genome, there has been time left for genome rearrangements implying a loss of GC-rich chromatin and one of the rDNA loci, whereas this has not occurred (almost not yet) in the Asian taxon, most probably younger.…”

“…This rDNA model almost absolutely agrees with the one of previously studied Asian Juniperus taxa (Nagano et al 2007). The number and location of 35S rDNA loci are the same in the diploid taxa, whereas in the tetraploid species here considered there is not a loci duplication (as it occurs in the Asian one), but only one locus (two signals) is observed, in agreement with the above-mentioned fact that there is only one chromosome pair with SC in J. thurifera.…”

“…With around 75 species and 100 taxa including infraspecific levels (Adams and Schwarzbach 2013), the genus Juniperus L. is the largest one of its family (Cupressaceae) and the second in the gymnosperms after Pinus L. It is very largely and abundantly distributed in Northern hemisphere, from sea level to mountains and from subtropical to arid zones, whereas it is extremely rare in the Southern hemisphere, with only one African taxon (Nagano et al 2007;Mao et al 2010;Adams and Schwarzbach 2013;Romo et al 2013). With two conspicuously distinct morphological patterns, acicular-and squamiform-leaved, the genus is monophyletic and is divided in three at their turn monophyletic sections: Caryocedrus Endl., comprising only one eastern Mediterranean species (J. drupacea Labill.…”

Gene flow between diploid and tetraploid junipers - two contrasting evolutionary pathways in two Juniperus populations

“…The ploidy levels of the taxa in this study except for the potential hybrid trees were previously published [ 7 , 16 , 23 , 24 ]. However, intra-specific variation in the ploidy level has been reported in this genus notably in J. sabina , J. chinensis L., and J. seravschanica Kom., [ 7 , 16 , 23 – 25 ] which makes essential the ploidy level determination of the studied populations.…”

Polyploidy in the Conifer Genus Juniperus: An Unexpectedly High Rate

“…(alerce) and Juniperus thurifera L. are tetraploid with 2 n = 4 x = 44 (Hair, 1968; Romo et al, 2013; Vallès et al, 2015). It is also notable that within Juniperus , the study of just three species revealed each had polyploid cytotypes in some populations (Sax and Sax, 1933; Nagano et al, 2007). These findings raise the question of whether polyploidy may be common in this genus and hence whether it has played a more significant role in the evolution of Cupressaceae than previously recognized in gymnosperms as a whole, and in conifers in particular.…”