Transgene effects on rhizodeposition: Evidence from molecular-chemical screening by Pyrolysis-Field Ionisation Mass Spectrometry (Py-FIMS)

Abstract

Rhizodeposition plays an important role in the C and N cycle of ecosystems, since it essentially reflects the interaction between plant, soil and soil microorganisms. The molecular-chemical characterisation of rhizodeposition is often limited to selected compound classes (e.g., carbohydrates and amino acids). A more comprehensive analytical approach is based on the molecular-chemical “fingerprint” revealed by Pyrolysis-Field Ionisation Mass Spectrometry (Py-FIMS).

The presented results give evidence of specific effects in conjunction with soil type, crop, variety, transgenes and mycorrhizal colonisation on the molecular-chemical composition of rhizodeposition. The experiments included various crops (maize, potato, vetch, willow and poplar), which were grown in leaching vessels under controlled environmental conditions on different soil types. The experimental design covered different varieties for maize, trangenes (vetch and potato) and inoculation with mycorrhizal fungi (poplar). All rhizodeposits were leached at defined growth stages and analysed by Py-FIMS.

The Py-FIMS data evaluation by multivariate statistics enabled a clear discrimination by all factors. Among these factors soil type and the crop had the largest effect on the molecular-chemical composition. By contrast, variety and transgene effects were subordinated.
The results of the multivariate statistics for crops, grown on the same soil (maize, potato, vetch), revealed 23 mass signals with highest discriminating power (P<0.001, multiple F-test). About 90 % of those signals can be assigned to known substances, based on our mass spectrometric in-house library and/or the literature. Further investigation will be focused on structural elucidation of the previously unassigned mass signals.
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