Analysis of intraspecific divergence of hexaploid wheat Triticum spelta L. by chromosome C-banding

Intraspecific divergence of hexaploid wheat Triticum spelta was studied by chromosome C-banding in 41 accessions of different geographic origins. The spelt accessions did not differ in karyotype structure or heterochromatin distribution from common wheat, but showed greater intraspecific polymorphism for chromosome rearrangements (translocations, inversions) and banding patterns. On evidence of C-banding patterns, spelt was assumed to occupy an intermediate position between tetraploid and hexaploid wheat species. Accessions of the Asian spelt subspecies had more diverse banding patterns than European accessions. A relatively high frequency of chromosome rearrangements was observed in Iranian accessions. Visual analysis revealed high uniformity of chromosome banding patterns in T. spelta populations of Afghanistan, Spain, and Germany (Bavarian group), suggesting a significant role of the founder effect in their evolution.     

History of modern chromosomal analysis. Differential staining of plant chromosomes

Differential staining methods found extensive use in karyotype studies of many plant and animal species and provide for reliable identification of all chromosomes of the organism. Below we describe the most widespread methods and history of their advent. In addition, we discuss specific structure of the chromosomes and possible mechanisms responsible for differential segmentation.     

A protease-activatable luminescent biosensor and reporter cell line for authentic SARS-CoV-2 infection

Efforts to define serological correlates of protection against COVID-19 have been hampered by the lack of a simple, scalable, standardised assay for SARS-CoV-2 infection and antibody neutralisation. Plaque assays remain the gold standard, but are impractical for high-throughput screening. In this study, we show that expression of viral proteases may be used to quantitate infected cells. Our assays exploit the cleavage of specific oligopeptide linkers, leading to the activation of cell-based optical biosensors. First, we characterise these biosensors using recombinant SARS-CoV-2 proteases. Next, we confirm their ability to detect viral protease expression during replication of authentic virus. Finally, we generate reporter cells stably expressing an optimised luciferase-based biosensor, enabling viral infection to be measured within 24 h in a 96- or 384-well plate format, including variants of concern. We have therefore developed a luminescent SARS-CoV-2 reporter cell line, and demonstrated its utility for the relative quantitation of infectious virus and titration of neutralising antibodies.     

Cytogenetic analysis of hybrids resistant to yellow rust and powdery mildew obtained by crossing common wheat (Triticum aestivum L., AABBDD) with wheat of the Timopheevi group (AtAtGG)

The karyotypes of 47 hybrid lines obtained from crosses of common wheat Triticum aestivum L. (cv. Rodina and line 353) with Triticum timopheevii Zhuk, (AtAtGG) and related species T. militinae Zhuk. et Migusch. (AtAtGG) and T. kiharae Dorof. et Migusch. (AtAtGGDsqDsq) were analyzed by C-banding. Most lines were resistant to yellow rust and powdery mildew. The introgression of alien genetic material to the common wheat genome was realized via substitutions of complete At-, G-, and D-genome chromosomes, chromosome arms, or their fragments. The pattern of chromosome substitutions in resistant lines differed from that in introgressive hybrids selected for other traits. Substitutions of chromosomes 6G, 2At, 2G, and 5G were revealed in 31, 23, 18, and 13 lines, respectively. Substitutions of chromosomes 4G-, 4At, and 6At were not observed. In 15 lines, a 5BS. 5BL-5GL translocation was identified. High frequency of substitutions of chromosomes 2At, 2G, 5G, and 6G indicate that they may carry the resistance genes and that they are closely related to the respective homoeologous chromosomes of common wheat that determines their high compensation ability.     

Highly syntenic regions in the genomes of soybean, <Emphasis Type="Italic">Medicago truncatula</Emphasis>, and <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

Background  

Recent genome sequencing enables mega-base scale comparisons between related genomes. Comparisons between animals, plants, fungi, and bacteria demonstrate extensive synteny tempered by rearrangements. Within the legume plant family, glimpses of synteny have also been observed. Characterizing syntenic relationships in legumes is important in transferring knowledge from model legumes to crops that are important sources of protein, fixed nitrogen, and health-promoting compounds.     

Instability of (GATA)<Subscript> n</Subscript> microsatellite loci in the parthenogenetic Caucasian rock lizard<Emphasis Type="Italic"> Darevskia unisexualis</Emphasis> (Lacertidae)

Mini- and microsatellites, comprising tandemly repeated short nucleotide sequences, are abundant dispersed repetitive elements that are ubiquitous in eukaryotic genomes. In humans and other bisexual species hypervariable mini- and microsatellite loci provide highly informative systems for monitoring of germline and somatic instability. However, little is known about the mechanisms by which these loci mutate in species that lack effective genetic recombination. Here, multilocus DNA fingerprinting was used to study M13 minisatellite and (GATA) _n microsatellite instability in the parthenogenetic Caucasian rock lizard Darevskia unisexualis (Lacertidae). DNA fingerprinting of 25 parthenogenetic families, from six isolated populations in Armenia (comprising a total of 84 siblings), using the oligonucleotide (GATA)₄ as a hybridization probe, revealed mutant fingerprinting phenotypes in 13 siblings that differed from their mothers in several restriction DNA fragments. In three families (8 siblings), the mutations were present in the germline. Moreover, the mutant fingerprint phenotypes detected in siblings were also present in population DNA samples. No intrafamily variations in DNA fingerprint patterns were observed with the M13 minisatellite probe. Estimates of the mutation rate for (GATA) _n microsatellite loci in D. unisexualis showed that it was as high as that seen in some bisexual species, reaching 15% per sibling or 0.95% per microsatellite band. Furthermore, in one case, a somatic (GATA) _n microsatellite mutation was observed in an adult lizard. These findings directly demonstrate that mutations in (GATA) _n microsatellite loci comprise an important source of genetic variation in parthenogenetic populations of D. unisexualis.Communicated by G. P. Georgiev     

Cytogenetic Analysis of Hybrids Resistant to Yellow Rust and Powdery Mildew Obtained by Crossing Common Wheat (Triticum aestivum L., AABBDD) with Wheats of the Timopheevi Group (AtAtGG)

The karyotypes of 47 hybrid lines obtained from crosses of common wheat Triticum aestivum L. (cv. Rodina and line 353) with Triticum timopheevii(Zhuk.) Zhuk. (A ^t A ^t GG) and related species T. militinae Zhuk. et Migusch. (A ^t A ^t GG) and T. kiharae Dorof. et Migusch. (A ^t A ^t GGD ^sq D ^sq) were analyzed by C-banding. Most lines were resistant to yellow rust and powdery mildew. The introgression of alien genetic material to the common wheat genome was realized via substitutions of complete A ⁺-,G-, and D-genome chromosomes, chromosome arms, or their fragments. The pattern of chromosome substitutions in resistant lines differed from that in introgressive hybrids selected for other traits. Substitutions of chromosomes 6G, 2A^t, 2G, and 5G were revealed in 31, 23, 18, and 13 lines, respectively. Substitutions of chromosomes 4G, 4A^t, and 6A^t were not observed. In 15 lines, a 5BS.5BL-5GL translocation was identified. High frequency of substitutions of chromosomes 2A^t, 2G, 5G, and 6G indicate that they may carry the resistance genes and that they are closely related to the respective homoeologous chromosomes of common wheat that determines their high compensation ability.     

Comparative cytogenetic analysis of hexaploid <Emphasis Type="Italic">Avena</Emphasis> L. species

Using C-banding method and in situ hybridizatiion with the 45S and 5S rRNA gene probes, six hexaploid species of the genus Avena L. with the ACD genome constitution were studied to reveal evolutionary karyotypic changes. Similarity in the C-banding patterns of chromosomal patterns and in the patterns of distribution of the rRNA gene families suggests a common origin of all hexaploid species. Avena fatua is characterized by the broadest intraspecific variation of the karyotype; this species displays chromosomal variants typical of other hexaploid species of Avena. For instance, a translocation with the involvement of chromosome 5C marking A. occidentalis was discovered in many A. fatua accessions, whereas in other representatives of this species this chromosome is highly similar to the chromosome of A. sterilis. Only A. fatua and A. sativa show slight changes in the morphology and in the C-banding pattern of patterns of chromosome 2C. These results can be explained either by a hybrid origin of A. fatua or by the fact that this species is an intermediate evolutionary form of hexaploid oats. The 7C–17 translocation was identified in all studied accessions of wild and weedy species (A. sterilis, A. fatua, A. ludoviciana, and A. occidentalis) and in most A. sativa cultivars, but it was absent in A. byzantina and in two accessions of A. sativa. The origin and evolution of the Avena hexaploid species are discussed in context of the results.     

Nocturne for an unknown pollinator: first description of a night‐flowering orchid (Bulbophyllum nocturnum)

Bulbophyllum nocturnum , a species of section Epicrianthes from New Britain, is described and illustrated. It is the first known example of an orchid species in which the flowers open after dark and close in the morning. The poorly understood pollination biology of section Epicrianthes, a clade with highly unusual flowers, is discussed. Attention is drawn to the close resemblance between the petal appendages of some species and the fruiting bodies of certain Myxogastria. © 2011 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, 167 , 344–350.     

Intraspecific divergence in wheats of the Timopheevi group as revealed by in situ hybridization with tandem repeats of the Spelt1 and Spelt52 families

Fluorescent in situ hybridization (FISH) was used to study the distribution of the Spelt1 and Spelt52 repetitive DNA sequences on chromosomes of ten accessions representing three polyploid wheat species of the Timopheevi group: Triticum araraticum (7), T. timopheevii (2), and T. kiharae (1). Sequences of both families were found mostly in the subtelomeric chromosome regions of the G genome. The total number of Spelt1 sites varied from 8 to 14 in the karyotypes of the species under study; their number, location, and size differed among the seven T. araraticum accessions and were the same in the two T. timopheevii accessions and T. kiharae, an amphidiploid T. timopheevii-Aegilops tauschii hybrid. The Spelt52 tandem repeat was detected in the subtelomeric regions of chromosomes 1-4; its sites did not coincide with the Spelt1 sites. The chromosome distribution and signal intensity of the Spelt52 repeats varied in T. araraticum and were the same in T. timopheevii and T. kiharae. The chromosome distributions of the Spelt1 and Spelt52 repeats were compared for the polyploid wheats of the Timopheevi group and diploid Ae. speltoides, a putative donor of the G genome. The comparison revealed a decrease in hybridization level: both the number of sites per genome and the size of sites were lower. The decrease was assumed to result from repeat elimination during polyploidization and subsequent evolution of wheat and from the founder effect, since the origin of Timopheevi wheats might involve the genotype of Ae. speltoides, which is highly polymorphic for the distribution of Spelt1 and Spelt52 sequences and is similar in the chromosome location of the repeats to modern wheat.