Doerte Harpke

5.8S motifs for the identification of pseudogenic ITS regions

The internal transcribed spacer (ITS) region (ITS1, 5.8S rDNA, ITS2) represents one of the most popular molecular markers in phylogenetics. The number of investigations revealing high degrees of intra-individual polymorphism connected with the presence of pseudogenic ITS regions is on the increase. Studies including pseudogenic ITS regions can lead to erroneous phylogenetic trees and false taxonomic conclusions. For their recognition, we focus on the 5.8S rDNA as the functional part of this region, which is also affected by degeneration processes. We outline three conserved Viridiplantae 5.8S motifs: GAATTGCAGAAwyC, TTTGAAyGCA, CGATGAAGAACGyAGC, which can be simply checked in sequence alignments. The latter 5.8S motif we also recognised in the large subunit RNA (LSU) of Escherichia coli. The utility of different methods for pseudogene detection based on easily recognisable 5.8S sequence motifs by comparison with 5.8S secondary structure reconstructions and statistical tests are discussed and illustrated w...

Extensive 5.8S nrDNA polymorphism in Mammillaria (Cactaceae) with special reference to the identification of pseudogenic internal transcribed spacer regions

The internal transcribed spacer (ITS) region (ITS1, 5.8S rDNA, ITS2) represents the most widely applied nuclear marker in eukaryotic phylogenetics. Although this region has been assumed to evolve in concert, the number of investigations revealing high degrees of intra-individual polymorphism connected with the presence of pseudogenes has risen. The 5.8S rDNA is the most important diagnostic marker for functionality of the ITS region. In Mammillaria, intra-individual 5.8S rDNA polymorphisms of up to 36% and up to nine different types have been found. Twenty-eight of 30 cloned genomic Mammillaria sequences were identified as putative pseudogenes. For the identification of pseudogenic ITS regions, in addition to formal tests based on substitution rates, we attempted to focus on functional features of the 5.8S rDNA (5.8S motif, secondary structure). The importance of functional data for the identification of pseudogenes is outlined and discussed. The identification of pseudogenes is essential, because they may cause erroneous phylogenies and taxonomic problems.

New insights into the phylogeny and taxonomy of Chinese species of Gagea (Liliaceae)—speciation through hybridization

A new region of speciation for the genus Gagea (Liliaceae) was investigated (Bogda-Shan and Urumqi; northwestern Xinjiang, China). Two species were recorded as new for the region (G. rufidula, G. davlianidzeae); three species are described as new to science (G. angelae, G. jensii and G. huochengensis). The description of G. nigra is emendated. Sequence data (cpDNA: trnL-trnF IGS+psbA-trnH IGS, nrDNA: ITS), including representatives of all Gagea sections, were used to compare the new species with closely related taxa. A nuclear single copy gene region (pCOS At103) was analysed for representatives of the Sects. Minimae and Gagea. Network analysis of cpDNA and nDNA indicates hybridization and recent speciation in Xinjiang. ITS and pCOS At103 sequences reveal gene flow between G. davlianidzeae and G. nigra. A cpDNA haplotype network constructed from representatives of Sect. Gagea was highly informative phylogenetically. Gagea angelae and G. huochengensis, sharing gene flow, are related closely to a basal clade represented by G. ancestralis, G. xiphoidea and G. capusii, which may include the putative progenitor of all other taxa of the large Eurasian Sect. Gagea. Whereas speciation in Sect. Minimae seems to be driven mainly by hybridization, speciation in the Sect. Gagea may be influenced by both hybridization and geographical separation. We confirm the monophyly of Sects. Bulbiferae and Minimae.

Gagea bohemica (Liliaceae), a highly variable monotypic species within Gagea sect. Didymobulbos

Abstract Gagea bohemica s.l. (Liliaceae) consists of two morphologically extreme forms (saxatilis and bohemica) which depending on the varying opinions of the authors are considered as separate species, subspecies or as a single variable species. In this study, morphological (form and length of perianth segments, pilosity of pedicles and peduncles) and molecular data (cpDNA trnL–trnF IGS) of 55 samples corresponding to 43 populations from Western Europe to the Mediterranean area and eastern Caucasus were investigated. G. bohemica (Zauschn.) Schult. & Schult. f. represents a highly variable monotypic species from both morphological and karyological (2n = 24, 36, 48, 60, 72) aspects. Based on the molecular and morphological data presented here, a differentiation between specific and infraspecific taxa is not possible. We hypothesize that the morphological variability of this species is largely influenced by different site conditions and ploidy level.

Quantitative PCR Revealed a Minority of ITS Copies to Be Functional in Mammillaria (Cactaceae)

The increasing number of pseudogenic internal transcribed spacer (ITS) regions (ITS1, 5.8S rDNA, ITS2) reported for plant taxa raises questions—for example, concerning the proportion of functional copies. Our application of quantitative PCR (qPCR) with genomic DNA under stringent conditions revealed that <3% of the copies of the ITS region were putatively functional in the genomic PCR pool in Mammillaria. The selective amplification of functional copies of the ITS region was possible through the utilization of conserved angiosperm motifs (ITS1 motif and 5.8S motif) as primer annealing sites. Our study displays that it is possible to quantify the proportion of functional copies of repetitive DNA regions through their selective amplification by qPCR.

A Matter of Contrast: Yellow Flower Colour Constrains Style Length in Crocus species.

Most flowers display distinct colour patterns comprising two different areas. The peripheral large-area component of floral colour patterns attracts flower visitors from some distance and the central small-area component guides flower visitors towards landing sites. Whereas the peripheral colour is largely variable among species, the central colour, produced mostly by anthers and pollen or pollen mimicking floral guides, is predominantly yellow and UV-absorbing. This holds also for yellow flowers that regularly display a UV bull’s eye pattern. Here we show that yellow-flowering Crocus species are a noticeable exception, since yellow-flowering Crocus species–being entirely UV-absorbing–exhibit low colour contrast between yellow reproductive organs and yellow tepals. The elongated yellow or orange-yellow style of Crocus flowers is a stamen-mimicking structure promoting cross-pollination by facilitating flower visitors’ contact with the apical stigma before the flower visitors are touching the anthers. Since Crocus species possess either yellow, violet or white tepals, the colour contrast between the stamen-mimicking style and the tepals varies among species. In this study comprising 106 Crocus species, it was tested whether the style length of Crocus flowers is dependent on the corolla colour. The results show that members of the genus Crocus with yellow tepals have evolved independently up to twelve times in the genus Crocus and that yellow-flowering Crocus species possess shorter styles as compared to violet- and white-flowering ones. The manipulation of flower visitors by anther-mimicking elongated styles in Crocus flowers is discussed.