Fungal association and root morphology shift stepwise during ontogenesis of orchid Cremastra appendiculata towards autotrophic nutrition

The chlorophyllous, terrestrial orchid Cremastra appendiculata from East Asia is unique concerning its fungal mycorrhiza partners. The initially mycoheterotrophic protocorms exploit rather specialized non-rhizoctonia saprotrophic Psathyrellaceae. Adult individuals of this orchid species are either linked to Psathyrellaceae being partially mycoheterotrophic or form mycorrhiza with fungi of the ubiquitous saprotrophic rhizoctonia group. This study provides new insights on nutrition mode, subterranean morphology and fungal partners across different life stages of C. appendiculata. We compared different development stages of C. appendiculata to surrounding autotrophic reference plants based on multi-element natural abundance stable isotope analyses (δ(13)C, δ(15)N, δ(2)H, δ(18)O) and total N concentrations. Site- and sampling-time-independent enrichment factors of stable isotopes were used to reveal trophic strategies. We determined mycorrhizal fungi of C. appendiculata protocorm, seedling and adult samples using high-throughput DNA sequencing. We identified saprotrophic non-rhizoctonia Psathyrellaceae as dominant mycorrhizal fungi in protocorm and seedling rhizomes. In contrast, the roots of seedlings and mature C. appendiculata were mainly colonized with fungi belonging to the polyphyletic assembly of rhizoctonia (Ceratobasidium, Thanatephorus and Serendipitaceae). Mature C. appendiculata did not differ in isotopic signature from autotrophic reference plants suggesting a fully autotrophic nutrition mode. Characteristic of orchid specimens entirely relying on fungal nutrition, C. appendiculata protocorms were enriched in (15)N, (13)C and (2)H compared to reference plants. Seedlings showed an intermediate isotopic signature, underpinning the differences in the fungal community depending on their subterranean morphology. In contrast to the suggestion that C. appendiculata is a partially mycoheterotrophic orchid species, we provide novel evidence that mature C. appendiculata with rhizoctonia mycobionts can be entirely autotrophic. Besides an environmentally driven variability among populations, we suggest high within-individual flexibility in nutrition and mycobionts of C. appendiculata, which is subject to the ontogenetic development stage

Drying-Rewetting and Flooding Impact Denitrifier Activity Rather than Community Structure in a Moderately Acidic Fen

Wetlands represent sources or sinks of the greenhouse gas nitrous oxide (N2O). The acidic fen Schlöppnerbrunnen emits denitrification derived N2O and is also capable of N2O consumption. Global warming is predicted to cause more extreme weather events in future years, including prolonged drought periods as well as heavy rainfall events, which may result in flooding. Thus, the effects of prolonged drought and flooding events on the abundance, community composition, and activity of fen denitrifiers were investigated in manipulation experiments. The water table in the fen was experimentally lowered for 8 weeks in 2008 and raised for 5.5 months in 2009 on three treatment plots, while three plots were left untreated and served as controls. In situ N2O fluxes were rather unaffected by the drought treatment and were marginally increased by the flooding treatment. Samples were taken before and after treatment in both years. The structural gene markers narG and nosZ were used to assess possible changes in the nitrate reducer and denitrifier community in response to water table manipulations. Detected copy numbers of narG and nosZ were essentially unaffected by the experimental drought and flooding. Terminal restriction fragment length polymorphism (TRFLP) patterns of narG and nosZ were similar before and after experimental drought or experimental flooding, indicating a stable nitrate reducer and denitrifier community in the fen. However, certain TRFs of narG and nosZ transcripts responded to experimental drought or flooding. Nitrate-dependent Michaelis-Menten kinetics were assessed in anoxic microcosms with peat samples taken before and 6 months after the onset of experimental flooding. Maximal reaction velocities vmax were higher after than before flooding in samples from treament but not in those from control plots taken at the same time. The ratio of N2O to N2O + N2 was lower in soil from treatment plots after flooding than in soil from control plots, suggesting mitigation of N2O emissions by increased N2O-reduction rates after flooding. N2O was consumed to subatmospheric levels in all microcosms after flooding. The collective data indicate that water table manipulations had only minor effects on in situ N2O fluxes, denitrifier abundance, and denitrifier community composition of the acidic fen, while active subpopulations of denitrifiers changed in response to water table manipulations, suggesting functionally redundant subpopulations occupying distinct ecological niches in the fen

On the way to specifically targeting minimal residual disease?

The target of all adjuvant systemic therapies after surgery in breast cancer is the eradication of a minimal subclinical residual disease. Although it is well known that tumor cell dissemination takes place already at an early stage of the disease, little is known about the tumorbiological parameters of these residual cells. Selection of patients eligible for adjuvant endocrine therapies is based on the analysis of receptor expression in the primary tumor – although the analysis is directed against disseminated tumor cells, these cells may vary in receptor expression in comparison with the primary tumor

Dinner with the roommates : trophic niche differentiation and competition in a mutualistic ant-ant association

1. The potential for competition is highest among species in close association. Despite net benefits for both parties, mutualisms can involve costs, including food competition. This might be true for the two neotropical ants Camponotus femoratus and Crematogaster levior, which share the same nest in a presumably mutualistic association (parabiosis). 2. While each nest involves one Crematogaster and one Camponotus partner, both taxa were recently found to comprise two cryptic species that show no partner preferences and seem ecologically similar. Since these cryptic species often occur in close sympatry, they might need to partition their niches to avoid competitive exclusion. 3. Here, we investigated first, is there interference competition between parabiotic Camponotus and Crematogaster, and do they prefer different food sources under competition? And second, is there trophic niche partitioning between the cryptic species of either genus? 4. Using cafeteria experiments, neutral lipid fatty acid and stable isotope analyses, we found evidence for interference competition, but also trophic niche partitioning between Camponotus and Crematogaster. Both preferred protein- and carbohydrate-rich baits, but at protein-rich baits Ca. femoratus displaced Cr. levior over time, suggesting a potential discovery-dominance trade-off between parabiotic partners. Only limited evidence was found for trophic differentiation between the cryptic species of each genus. 5. Although we cannot exclude differentiation in other niche dimensions, we argue that neutral dynamics might mediate the coexistence of cryptic species. This model system is highly suitable for further studies of the maintenance of species diversity and the role of mutualisms in promoting species coexistence

Impact of Global Climate Change on the European Barley Market Requires Novel Multi-Method Approaches to Preserve Crop Quality and Authenticity

Most recently in 2018 and 2019, large parts of Europe were affected by periods of massive drought. Resulting losses in cereal yield pose a major risk to the global supply of barley, as more than 60% of global production is based in Europe. Despite the arising price fluctuations on the cereal market, authenticity of the crop must be ensured, which includes correct declaration of harvest years. Here, we show a novel approach that allows such differentiation for spring barley samples, which takes advantage of the chemical changes caused by the extreme drought. Samples from 2018 were successfully differentiated from those of 2017 by analysis of changes in near-infrared spectra, enrichment in the isotope (13)C, and strong accumulation of the plant-physiological marker betaine. We demonstrate that through consideration of multiple modern analysis techniques, not only can fraudulent labelling be prevented, but indispensable knowledge on the drought tolerance of crops can be obtained

Dark septate endophytes and arbuscular mycorrhizal fungi (Paris‐morphotype) affect the stable isotope composition of 'classically' non-mycorrhizal plants

The vast majority of terrestrial plants exchange nutrients with fungal partners forming different mycorrhizal types. The minority of plants considered as non-mycorrhizal, however, are not necessarily free of any fungi, but are frequently colonized by elusive fungal endophytes, such as dark septate endophytes (DSE) or fine root endophytes (FRE). While a functional role of FRE in improvement of nutrient gain was recently elucidated, the function of DSE is still in discussion and was here addressed for 36 plant species belonging to the families Equisetaceae, Cypereaceae and Caryophyllaceae. Molecular and microscopic staining approaches were conducted to verify the presence of DSE in the investigated species. Stable isotope natural abundances of the elements carbon, nitrogen, hydrogen and oxygen and total nitrogen concentrations were analyzed for the respective species of the target plant families and accompanying mycorrhizal and non-mycorrhizal (Brassicaceae) plant species. Staining approaches confirmed the presence of DSE in all investigated species within the families Equisetaceae, Cyperaceae and Caryophyllaceae. A co-colonization with Paris-type arbuscular mycorrhiza (AM) was occasionally found by staining and molecular approaches in species of the Equisetaceae. Species of the Equisetaceae, Cyperaceae and Caryophyllaceae were significantly 15N-enriched in comparison to accompanying plants. In addition, a significant 13C and 2H enrichment and increased total nitrogen concentrations were found for representatives of the Equisetaceae. The 15N-enrichment found here for representatives of Equisetaceae, Cyperaceae and Caryophyllaceae provides evidence for a functional role of the ubiquitous DSE fungi. DSE fungi obviously provide access to 15N-enriched soil organic compounds probably in exchange for organic carbon compounds from plant photosynthesis. As indicated by additional 13C- and 2H-enrichments, representatives of the Equisetaceae apparently gain simultaneously organic carbon compounds from their AM fungi of the Paris-morphotype. Thus, species of the Equisetaceae have to be considered as partially, or in case of the achlorophyllous fertile Equisetum arvense, as fully mycoheterotrophic at least in some stages of their life cycle. So far mostly underappreciated fungi classified as DSE are suggested to occupy an ecologically relevant role similar to mycorrhizae and the occurrence of simultaneous functions of DSE and AM fungi in Equisetaceae is proposed