Abstract
(Sub-project to 838.06.090) Key to a fertile and healthy soil ecosystem is a high bioturbation rate, rapid decomposition and mineralization. Soil invertebrates that belong to the detrital food web are essential for proper soil ecosystem function, and as such, they control carbon and nutrient flows, thereby stimulating plant nutrient uptake. Several recent studies showed that growing GM crops may have significant detrimental impact on both above and below ground invertebrates, which raises particular concern over the effect of GM crops on above mentioned key soil ecosystem processes. Currently there is no suitable system available to monitor proper soil ecosystem functioning. This proposal aims to fill this gap. Here we propose to test the effects of GM crops on soil decomposition and bioturbation. Three functional dissimilar groups of soil based invertebrates (macrordetritivores, microbivores and bioturbators) will be applied to evaluate the effects of crop plants on the soil ecosystem. In order to maximise the expected effects we propose to use GM and non-GM plants with enhanced glucosinolate (GS) contents. Especially plants containing aliphatic GSs are already used for biofumigation of soil and they are known to have a detrimental effect on soil decomposers. Since these compounds are considered to have beneficial nutritional properties for humans, novel crop varieties (GM and non-GM) with enhanced levels of these antimicrobial compounds are likely to be introduced in the future and thus, use of these plants not only provides a suitable test system, but also represent a realistic GM-scenario. Furthermore, these compounds and their associated oxidised forms can be followed and quantified throughout the experiments. Our main goal is to study effects of GM crop on the detritus food web. We aim to establish a decision matrix to assess the risk of GM crop on model soil invertebrates that maintain essential soil functions such as decomposition and mineralization. The following sub-objectives are formulated to reach this goal: 1) Estimate environmental effect concentrations on soil invertebrates caused by GM products using internationally standardized (ISO, OECD) ecotoxicological guidelines and feeding trails. 2) To generate GM cruciferous plant genotypes with enhanced GS synthesis, exceeding current non-GM genotypes to ensure maximal effects on soil invertebrates 3) To determine direct and indirect effects of high GS plants on community structure and soil functioning by measuring changes in soil nutrient dynamics. 4) To identify expression markers that reflect negative effects on soil invertebrates caused by GM compounds and to validate these genetic markers that can be used as a fast and sensitive tool in risk assessment of GM Crops. 5) To interpret responses to GM plants at the community level in the context of soil risk assessment by integrating data generated from this project with baseline data on biomass and abundance of soil invertebrates. As model system, we will focus on four species of potentially vulnerable groups of soil invertebrates: Eisenia fetida (earthworm, bioturbator), Protaphorura armata, Folsomia candida (Collembola, microbivorous) and Porcellio scaber (Isopod, macrodetritivorous). These key species are chosen for their essential beneficial effects on soil functioning and their relevance in current soil risk assessment. As plant models we will use GM and non-GM on Brassica oleracea and Brassica rapa variants with elevated GS contents. Funding for a PhD student and a post-doc is requested. The PhD student will develop standardized ecotoxicological tests to assess the survival and reproduction of soil invertebrates and will perform transcript profiling of GS exposed Eisenia and Folsomia. Potential deviations from transcriptional profiles generated by exposure of soil invertebrates to natural Dutch soil types (NOR, currently established within the Ecogenomics consortium) will form the basis to classify the GM crop impact on soil decomposers and bioturbators. The post-doc will design constructs for genetic modification of Cruciferous plants to enhance glucosinolate production tissue-specifically, initially of Arabidopsis thaliana to test constructs and subsequently in well-transformable Brassica varieties. GM plants developed by the post-doc will be tested by the PhD student in feeding trials and microcosm experiments. Feeding trials will expose a root-feeding soil invertebrate (P. armata) to root tissue from the GM crops and detect effects on reproduction and survival. Microcosm experiments will test the effects of high GS Brassica crops on soil detritivorous community structure, in particular nutrient dynamics important for soil fertility.
Netherlands