Variable amounts of DNA related to the size of chloroplasts III. Biochemical determinations of DNA amounts per organelle

Plastid genomes (plastomes) are part of the integrated compartmentalised genetic system of photoautotrophic eukaryotes. They are highly redundant and generally dispersed in several regions (nucleoids) within organelles. DNA quantities and number of DNA-containing regions per plastid vary and are developmentally regulated in a way not yet understood. Reliable quantitative data describing these patterns are scarce. We present a protocol to isolate fractions of pure plastids with varying average sizes from leaflets (≤1 mm) and leaves of different developmental stages continuously up to maturity (25 cm) from Beta vulgaris L. (sugar beet) to determine DNA amounts per organelle. The approach is based on plastid purification from homogenates of moderately fixed tissue by differential and isopycnic gradient centrifugations and on application of two different DNA specific colorimetric reactions after removing potentially interfering compounds. The sensitive fluorochrome DAPI (4′,6-diamidino-2-phenylindole) was used to estimate numbers and emission intensity of nucleoids per plastid. The amounts determined ranged from 0.15 to 4.9 × 10−2 pg DNA for plastids of 1→8 μm average diameter, corresponding from approximately a dozen to 330 genome equivalents per organelle and on average four to seven copies per nucleoid. The ratio of plastid/nuclear DNA changed continuously during leaf development from as little as 0.4% to about 20% in fully developed leaves. On the other hand, mesophyll cells of mature leaves differing in ploidy (di-, tri- and tetraploid) appeared to maintain a relatively constant nuclear genome/plastome ratio, equivalent to about 1,700 copies per C-value

Karyotype and nuclear DNA content of hexa-, octo-, and duodecaploid lines of Bromus subgen. Ceratochloa

The subgenus Ceratochloa of the genus Bromus includes a number of closely related allopolyploid forms or species that present a difficult taxonomic problem. The present work combines data concerning chromosome length, heterochromatin distribution and nuclear genome size of different 6x, 8x and 12x accessions in this subgenus. Special attention is paid to the karyotype structure and genomic constitution of duodecaploid plants recently found in South America. Hexaploid lineages possess six almost indistinguishable genomes and a nuclear DNA content between 12.72 pg and 15.10 pg (mean 1Cx value = 2.32 pg), whereas octoploid lineages contain the same six genomes (AABBCC) plus two that are characterized by longer chromosomes and a greater DNA content (1Cx = 4.47 pg). Two duodecaploid accessions found in South America resemble each other and apparently differ from the North American duodecaploid B. arizonicus as regards chromosome size and nuclear DNA content (40.00 and 40.50 pg vs. 27.59 pg). These observations suggest that the South American duodecaploids represent a separate evolutionary lineage of the B. subgenus Ceratochloa, unrecognized heretofore

Cytogenetyka Tradescantia spathacea (syn. Rhoeo spathacea). Artykuł przeglądowy

As a favorable PTH (permanent translocation heterozygosity) model, Tradescantia spathacea (synon. Rhoeo spathacea) offers an unusual opportunity to address crucial cytogenetic problems, among them complex chromosome rearrangements, recognition and segregation of translocated genome parts, the relation of crossing-over to synaptic processes. Here I present the existing knowledge on T. spathacea with the intention to reestablish it for advanced cytogenetic research.Tradescantia spathacea (syn. Rhoeo spathacea) jako tzw. permanentna heterozygota translokacyjna jest cennym organizmem modelowym do rozwiązywania ważnych problemów współczesnejcytogenetyki. Wśród nich są: kompleksowe chromosomowe rearanżacje, koniugacja i segregacja translokacyjnych segmentów, relacja pomiędzy crossing-over a procesami związanymi z koniugacją. W niniejszym artykule został przedstawiony istniejący stan wiedzy dotyczącej cytogenetyki T. spathacea oraz zostały poruszone najważniejsze zagadnienia z nią związane

Cytogenetics of Tradescantia spathacea (syn. Rhoeo spathacea). A review

As a favorable PTH (permanent translocation heterozygosity) model, Tradescantia spathacea (synon. Rhoeo spathacea) offers an unusual opportunity to address crucial cytogenetic problems, among them complex chromosome rearrangements, recognition and segregation of translocated genome parts, the relation of crossing-over to synaptic processes. Here I present the existing knowledge on T. spathacea with the intention to reestablish it for advanced cytogenetic research.Tradescantia spathacea (syn. Rhoeo spathacea) jako tzw. permanentna heterozygota translokacyjna jest cennym organizmem modelowym do rozwiązywania ważnych problemów współczesnejcytogenetyki. Wśród nich są: kompleksowe chromosomowe rearanżacje, koniugacja i segregacja translokacyjnych segmentów, relacja pomiędzy crossing-over a procesami związanymi z koniugacją. W niniejszym artykule został przedstawiony istniejący stan wiedzy dotyczącej cytogenetyki T. spathacea oraz zostały poruszone najważniejsze zagadnienia z nią związane

Variability of stem morphology in Lycopodium clavatum (Lycopodiaceae) is not related to ploidy level

Background and aims – Based on pedicel length, three morphological forms of Lycopodium clavatum L. are recognized. It has been previously reported that these are correlated with the ploidy level. The present investigation compares for the first time in Poland the diversity in pedicel length with the corresponding nuclear DNA amount and the ploidy level of L. clavatum. We aimed to find correlation between the morphotypes and the ploidy level in the Polish population of L. clavatum.Methods – Samples of shoots were taken from two clumps of L. clavatum. The ploidy level and 2C DNA content analysis was combined with pedicel length measurements. The ploidy level and genome size estimation were performed using flow cytometry.Key results – We found the occurrence of two morphological types of generative stems. The morphotype A produced distinct long pedicels (10.8–43.3 mm). The morphotype B had visible, but very short pedicels (4.5–9.3 mm). We tested the already existing hypothesis, according to which the A and B morphotypes represent respectively diploid and triploid ploidy level. Surprisingly, we did not find such a correlation. Regardless of the morphotype, all the studied plants were diploid, with 5.04–5.13 pg/2C nuclear DNA content.Conclusions – The occurrence of stems of different morphology in L. clavatum was not linked to the ploidy level. It is not excluded that the morphotypes may be genetically determined, but in the studied material, the ploidy level is certainly not at the origin of their differentiation

Variability of stem morphology in Lycopodium clavatum (Lycopodiaceae) is not related to ploidy level

Background and aims – Based on pedicel length, three morphological forms of Lycopodium clavatum L. are recognized. It has been previously reported that these are correlated with the ploidy level. The present investigation compares for the first time in Poland the diversity in pedicel length with the corresponding nuclear DNA amount and the ploidy level of L. clavatum. We aimed to find correlation between the morphotypes and the ploidy level in the Polish population of L. clavatum.Methods – Samples of shoots were taken from two clumps of L. clavatum. The ploidy level and 2C DNA content analysis was combined with pedicel length measurements. The ploidy level and genome size estimation were performed using flow cytometry.Key results – We found the occurrence of two morphological types of generative stems. The morphotype A produced distinct long pedicels (10.8–43.3 mm). The morphotype B had visible, but very short pedicels (4.5–9.3 mm). We tested the already existing hypothesis, according to which the A and B morphotypes represent respectively diploid and triploid ploidy level. Surprisingly, we did not find such a correlation. Regardless of the morphotype, all the studied plants were diploid, with 5.04–5.13 pg/2C nuclear DNA content.Conclusions – The occurrence of stems of different morphology in L. clavatum was not linked to the ploidy level. It is not excluded that the morphotypes may be genetically determined, but in the studied material, the ploidy level is certainly not at the origin of their differentiation

Molecular Marker Systems for Oenothera Genetics

The genus Oenothera has an outstanding scientific tradition. It has been a model for studying aspects of chromosome evolution and speciation, including the impact of plastid nuclear co-evolution. A large collection of strains analyzed during a century of experimental work and unique genetic possibilities allow the exchange of genetically definable plastids, individual or multiple chromosomes, and/or entire haploid genomes (Renner complexes) between species. However, molecular genetic approaches for the genus are largely lacking. In this study, we describe the development of efficient PCR-based marker systems for both the nuclear genome and the plastome. They allow distinguishing individual chromosomes, Renner complexes, plastomes, and subplastomes. We demonstrate their application by monitoring interspecific exchanges of genomes, chromosome pairs, and/or plastids during crossing programs, e.g., to produce plastome–genome incompatible hybrids. Using an appropriate partial permanent translocation heterozygous hybrid, linkage group 7 of the molecular map could be assigned to chromosome 9·8 of the classical Oenothera map. Finally, we provide the first direct molecular evidence that homologous recombination and free segregation of chromosomes in permanent translocation heterozygous strains is suppressed