A key feature of life's diversity is that some species are common but many more are rare. Nonetheless, at global scales, we do not know what fraction of biodiversity consists of rare species. Here, we present the largest compilation of global plant diversity to quantify the fraction of Earth's plant biodiversity that are rare. A large fraction, ~36.5% of Earth's ~435,000 plant species, are exceedingly rare. Sampling biases and prominent models, such as neutral theory and the k-niche model, cannot account for the observed prevalence of rarity. Our results indicate that (i) climatically more stable regions have harbored rare species and hence a large fraction of Earth's plant species via reduced extinction risk but that (ii) climate change and human land use are now disproportionately impacting rare species. Estimates of global species abundance distributions have important implications for risk assessments and conservation planning in this era of rapid global change.
Genes encoding ribosomal RNA (rDNA) are universal key constituents of eukaryotic genomes, and the nuclear genome harbours hundreds to several thousand copies of each species. Knowledge about the number of rDNA loci and gene copy number provides information for comparative studies of organismal and molecular evolution at various phylogenetic levels. With the exception of seed plants, the range of 45S rDNA locus (encoding 18S, 5.8S and 26S rRNA) and gene copy number variation within key evolutionary plant groups is largely unknown. This is especially true for the three earliest land plant lineages Marchantiophyta (liverworts), Bryophyta (mosses), and Anthocerotophyta (hornworts). In this work, we report the extent of rDNA variation in early land plants, assessing the number of 45S rDNA loci and gene copy number in 106 species and 25 species, respectively, of mosses, liverworts and hornworts. Unexpectedly, the results show a narrow range of ribosomal locus variation (one or two 45S rDNA loci) and gene copies not present in vascular plant lineages, where a wide spectrum is recorded. Mutation analysis of whole genomic reads showed higher (3-fold) intragenomic heterogeneity of Marchantia polymorpha (Marchantiophyta) rDNA compared to Physcomitrella patens (Bryophyta) and two angiosperms (Arabidopsis thaliana and Nicotiana tomentosifomis) suggesting the presence of rDNA pseudogenes in its genome. No association between phylogenetic position, taxonomic adscription and the number of rDNA loci and gene copy number was found. Our results suggest a likely evolutionary rDNA stasis during land colonisation and diversification across 480 myr of bryophyte evolution. We hypothesise that strong selection forces may be acting against ribosomal gene locus amplification. Despite showing a predominant haploid phase and infrequent meiosis, overall rDNA homogeneity is not severely compromised in bryophytes.
- MeSH
- Anthocerotophyta classification genetics MeSH
- Arabidopsis classification genetics MeSH
- Bryophyta classification genetics MeSH
- Chromosomes, Plant genetics MeSH
- Cytogenetic Analysis MeSH
- DNA, Plant genetics MeSH
- Species Specificity MeSH
- Phylogeny MeSH
- Gene Dosage MeSH
- In Situ Hybridization, Fluorescence MeSH
- Conserved Sequence MeSH
- Real-Time Polymerase Chain Reaction MeSH
- Hepatophyta classification genetics MeSH
- Evolution, Molecular MeSH
- DNA, Ribosomal genetics MeSH
- RNA, Ribosomal genetics MeSH
- RNA, Plant genetics MeSH
- Genes, Plant MeSH
- Embryophyta classification genetics MeSH
- Publication type
- Journal Article MeSH
Byl testován vliv abiotického elicitoru – AgNO3 v různých koncentracích na produkci flavonoidů v kalusové kultuře Ononis arvensis L. Použití tohoto abiotického elicitoru se osvědčilo pro zvýšení produkce flavonoidů v kultuře in vitro. Maximální produkce bylo dosaženo po 24 hodinové elicitaci AgNO3 v koncentraci c1 (0,5 mg/l) – zvýšení o 934 % oproti kontrole (bez působení elicitoru).
The study tested the effect of abiotic elicitor, AgNO3, in different concentrations, on the production of flavonoids in the callus culture Ononis arvensis L. The use of this abiotic elicitor proved to be good to increase the production of flavonoids in in vitro culture. The maximal production was achieved after a 24-hour elicitation with AgNO3 in a concentration c1 (0.5 mg/l) – an increase by 934 % versus the control (without the elicitor’s action).
- MeSH
- Biotechnology economics methods trends MeSH
- Silver Nitrate chemistry MeSH
- Research Support as Topic MeSH
- Flavonoids chemistry metabolism therapeutic use MeSH
- Humans MeSH
- Tissue Culture Techniques methods statistics & numerical data utilization MeSH
- Embryophyta classification MeSH
- Check Tag
- Humans MeSH
- Publication type
- Comparative Study MeSH
