Cytogenetic characterization of Hydrangea involucrata Sieb. and H. aspera D. Don complex (Hydrangeaceae): genetic, evolutional, and taxonomic implications

The subsection Asperae of genus Hydrangea L. (Hydrangeaceae) has been investigated for three reasons: several ambiguous classifications concerning Hydrangea aspera have been published, unexpected differences in genome size among seven accessions have been reported Cerbah et al. (Theor Appl Genet 103:45–51, 2001), and two atypical chromosome numbers (2n = 30 for Hydrangea involucrata and 2n = 34 for H. aspera) have been found when all other species of the genus present 2n = 36. Therefore, these two species and four subspecies of Hydrangea in all 29 accessions were analyzed for their genome size, chromosome number, and karyotype features. This investigation includes flow cytometric measurements of nuclear DNA content and bases composition (GC%), fluorochrome banding for detection of GC- and AT-rich DNA regions, and fluorescent in situ hybridisation (FISH) for chromosome mapping of 5 S and 18 S-5.8 S-26 S rDNA genes. In the H. aspera complex, the genome size ranged from 2.98 (subsp. sargentiana) to 4.67 pg/2C (subsp. aspera), an exceptional intraspecific variation of 1.57-fold. The mean base composition was 40.5% GC. Our report establishes the first karyotype for the species H. involucrata, and for the subspecies of H. aspera which indeed present different formulae, offering an element of discrimination. FISH and fluorochrome banding revealed the important differentiation between these two species (H. involucrata and H. aspera) and among four subspecies of the H. aspera complex. Our results are in agreement with the Chinese classification that places the groups Kawakami and Villosa as two different species: Hydrangea villosa Rehder and Hydrangea kawakami Hayata. This knowledge can contribute to effective germplasm management and horticultural use

Discovery of Juniperus sabina var. balkanensis R. P. Adams and A. N. Tashev in Macedonia, Bosnia-Herzegovina, Croatia and Central and Southern Italy and relictual polymorphisms found in nrDNA

Additional analyses of trnS-trnG and nrDNA from specimens from Bosnia-Herzegovina, southern and central, Italy, Croatia and Macedonia revealed the presence of J. sabina var. balkanensis in these areas west of the previously known populations in Greece, Bulgaria and western Turkey. Careful chromatogram analysis of eight (8) polymorphic sites in nrDNA revealed that nearly all of the populations of both var. balkanensis and var. sabina contained from 2 to 8 polymorphic sites. For these 8 heterozygous sites, two exclusive patterns were found in J. sabina. One type (GGACCCAG) was found in 16/62 plants and type 2 (ACGACAGT) was found in 4/62 plants. The majority of the plants examined (42/62) were heterozygous for 1 to 8 sites. These two nrDNA types appear to have arisen via hybridization with a J. thurifera ancestor. The two types appear in both v. sabina and v. balkanensis populations. Extant putative hybrids appear to have formed by crosses between present day type 1 and type 2 nrDNA. Publishe

Primula vulgaris (primrose) genome assembly, annotation and gene expression, with comparative genomics on the heterostyly supergene

Primula vulgaris (primrose) exhibits heterostyly: plants produce self-incompatible pin- or thrum-form flowers, with anthers and stigma at reciprocal heights. Darwin concluded that this arrangement promotes insect-mediated cross-pollination; later studies revealed control by a cluster of genes, or supergene, known as the S (Style length) locus. The P. vulgaris S locus is absent from pin plants and hemizygous in thrum plants (thrum-specific); mutation of S locus genes produces self-fertile homostyle flowers with anthers and stigma at equal heights. Here, we present a 411 Mb P. vulgaris genome assembly of a homozygous inbred long homostyle, representing ~87% of the genome. We annotate over 24,000 P. vulgaris genes, and reveal more genes up-regulated in thrum than pin flowers. We show reduced genomic read coverage across the S locus in other Primula species, including P. veris, where we define the conserved structure and expression of the S locus genes in thrum. Further analysis reveals the S locus has elevated repeat content (64%) compared to the wider genome (37%). Our studies suggest conservation of S locus genetic architecture in Primula, and provide a platform for identification and evolutionary analysis of the S locus and downstream targets that regulate heterostyly in diverse heterostylous species

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

8 p., tablas, fot. -- Post-print del artículo publicado en Tree Genetics and Genomes. Versión revisada y corregida.We carried out the first cytogenetic characterisation of Mediterranean species of Juniperus (Cupressaceae); to date, nuclear DNA amount and chromosome numbers were known, but a fine karyotype analysis had been only done in three eastern Asian taxa. We performed chromomycin A3 banding, for the first time in the family, and fluorescent in situ hybridisation (FISH) in order to detect 18S-5.8S-26S (also termed 35S and 45S) rRNA genes in five species of the genus, four diploid (Juniperus communis, Juniperus oxycedrus, Juniperus phoenicea and Juniperus sabina) and the only Mediterranean one that is exclusively tetraploid (Juniperus thurifera). The results show a very homogeneous pattern, with one chromosome pair with chromomycin-positive bands at the secondary constrictions and colocalised 35S rDNA signals. In diploid species, this model agrees with that of the two Asian taxa previously investigated with FISH. In the tetraploid species, conversely, the results are different: in the Asian taxa, signal number and location are exactly double in tetraploid than in diploid taxa, whereas in our case, the tetraploid species bears the same number of signals (not twice) as diploid ones. 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; this argument is a support for the ancient and relict character attributed to this taxon.This work has been subsidised by Ministerio de Ciencia e Innovación, Spanish government, Spain (projects CGL2010-22234-C02-01 and 02/BOS, CGL2013-49097-C2-2-P), Generalitat de Catalunya-Catalan government, Catalonia (2009/SGR/00439, 2014/SGR/514) and funds from CNRS and Université de Paris-Sud (Orsay). JV received a grant (2012BE100508) from AGAUR (Catalan government’s agency for university and research grants) for a research stay in the Laboratoire Ecologie, Systématique, Evolution, Université Paris-Sud at Orsay, in the frame of a sabbatical semester attributed to him by the Universitat de Barcelona.Peer reviewe