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Do genetic modifications in crops affect soil fungi? a review
No full textThe use of genetically modified (GM) plants in agriculture has been a topic in public debate for over a decade. Despite their potential to increase yields, there may be unintended negative side-effects of GM plants on soil micro-organisms that are essential for functioning of agro-ecosystems. Fungi are important soil organisms and can have beneficial or harmful effects on plants. Their benefits to agro-ecosystems come from their activities as free-living saprobes breaking down soil organic matter thereby releasing nutrients to the crops, as well as from mutualistic interactions. On the other hand, soil-borne plant pathogenic fungi can cause severe damage in crops. Understanding of the impact of GM plants on the dynamics and functioning of soil fungi is essential to evaluate the possible risks of introduction of GM plants for ecosystem functioning. In recent years, over 50 studies have addressed the effects of various GM traits in crops on soil fungal community structure and function. These studies showed that GM crops can have positive, negative, or neutral effects on both free-living and plant-associated soil fungi. The observed discrepancy in results of these studies is discussed. This is done by highlighting a number of case studies. New methods developed in recent years have enabled microbial ecologists to get a better picture on the functioning and assembly of soil fungal communities. This review presents and discusses two of the most promising methods which are also readily usable in risk assessment of GM plants on soil fungi and that could help answer remaining key questions in the field.
Occult progression by Apc-deficient intestinal crypts as a target for chemoprevention
No full textAlthough Apc mutation is widely considered an initiating event in colorectal cancer, little is known about the earliest stages of tumorigenesis following sporadic Apc loss. Therefore, we have utilized a novel mouse model that facilitates the sporadic inactivation of Apc via frameshift reversion of Cre in single, isolated cells and subsequently tracks the fates of Apc-deficient intestinal cells. Our results suggest that consistent with Apc being a 'gatekeeper', loss of Apc early in life during intestinal growth leads to adenomas or increased crypt fission, manifested by fields of mutant but otherwise normal-appearing crypts. In contrast, Apc loss occurring later in life has minimal consequences, with mutant crypts being less prone to either increased crypt fission or adenoma formation. Using the stem cell-specific Lgr5-CreER mouse, we generated different sized fields of Apc-deficient crypts via independent recombination events and found that field size correlates with progression to adenoma. To evaluate this early stage prior to adenoma formation as a therapeutic target, we examined the chemopreventive effects of sulindac on Apc-deficient occult crypt fission. We found that sulindac treatment started early in life inhibits the morphologically occult spread of Apc-deficient crypts and thus reduces adenoma numbers. Taken together these results suggest that: (i) earlier Apc loss promotes increased crypt fission, (ii) a field of Apc-deficient crypts, which can form via occult crypt fission or independent neighboring events, is an important intermediate between loss of Apc and adenoma formation and (iii) normal-appearing Apc-deficient crypts are potential unappreciated targets for cancer screening and chemoprevention.
Proceedings of the Plankton Ecology Group (PEG) Workshop in Mexico City (12–18 February 2012)
No full textPlankton is an important constituent of aquatic ecosystems, dominated in freshwater ecosystems by diverse groups of bacterioplankton, phytoplankton, and zooplankton. The Plankton Ecology Group (PEG) has made noteworthy headway in understanding ecosystem dynamics through a series of formal PEG meetings (a brief update can be found in Lürling 2013). The most recent PEG Workshop was hosted by the National Autonomous University of Mexico, 12–18 February 2012 (Lürling et al. 2012), organized under the auspices of SIL. The meeting was attended by 125 participants from 9 countries, the majority (>60%) of whom were young, enthusiastic students from various post-graduate programs in Mexico. The PEG working group chairman, Dr. Miquel Lürling, in his introduction to the workshop highlighted the salient contributions of PEG to general ecological plankton theory. The first plenary lecture during this meeting was delivered by the president of SIL, Dr. Brian Moss, followed by regular contributions, both oral and poster. Following the workshop, it was decided to publish selected lectures in the SIL journal, Inland Waters (IW). An editorial committee formed to assist with the peer review process selected 9 manuscripts for publication in a special PEG issue of Inland Waters. The contributions in this issue represent a wide range of planktonic organisms, including toxic cyanobacteria, and the physical and chemical conditions under which the organisms occur. Some authors discuss the role of competition, predation, or both in freshwater ecosystems.
Enhanced Input of Terrestrial Particulate Organic Matter Reduces the Resilience of the Clear-Water State of Shallow Lakes: A Model Study
No full textThe amount of terrestrial particulate organic matter (t-POM) entering lakes is predicted to increase as a result of climate change. This may especially alter the structure and functioning of ecosystems in small, shallow lakes which can rapidly shift from a clear-water, macrophyte-dominated into a turbid, phytoplankton-dominated state. We used the integrative ecosystem model PCLake to predict how rising t-POM inputs affect the resilience of the clear-water state. PCLake links a pelagic and benthic food chain with abiotic components by a number of direct and indirect effects. We focused on three pathways (zoobenthos, zooplankton, light availability) by which elevated t-POM inputs (with and without additional nutrients) may modify the critical nutrient loading thresholds at which a clear-water lake becomes turbid and vice versa. Our model results show that (1) increased zoobenthos biomass due to the enhanced food availability results in more benthivorous fish which reduce light availability due to bioturbation, (2) zooplankton biomass does not change, but suspended t-POM reduces the consumption of autochthonous particulate organic matter which increases the turbidity, and (3) the suspended t-POM reduces the light availability for submerged macrophytes. Therefore, light availability is the key process that is indirectly or directly changed by t-POM input. This strikingly resembles the deteriorating effect of terrestrial dissolved organic matter on the light climate of lakes. In all scenarios, the resilience of the clear-water state is reduced thus making the turbid state more likely at a given nutrient loading. Therefore, our study suggests that rising t-POM input can add to the effects of climate warming making reductions in nutrient loadings even more urgent.
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No full textThink ratio! A stoichiometric view on biodiversity-ecosystem functioning research
No full textEcological stoichiometry (ES) has become one of the most pervasive theoretical frameworks in environmental sciences and biology in the last two decades. ES allows predicting processes on all organizational levels from subcellular structures to ecosystems by relating the elemental composition and demand of organisms to the relative availability of resources. However, ES has been rarely used to understand and predict the relationship between biodiversity and ecosystem functioning (BEF), although ES would be ideally suited as it makes predictions on both population processes underlying biodiversity as well as on matter transformations underlying ecosystem processes. Here, we propose to link the two fields of research on ES and BEF relationships and highlight a number of potential avenues for further research. First, we cast a stoichiometric view on drivers of biodiversity change. Second, we address the stoichiometric underpinning of biodiversity-productivity relationships. Third, we discuss potential interactions between stoichiometry and diversity in a food web context.