Metabolic differentiation in the lichen Cladonia portentosa from different wet nitrogen deposition regimes’

Abstract

The deposition of atmospheric nitrogen is now recognized as a major driver of
biodiversity changes at mid to high latitudes. It has previously been shown that
regional variations in wet nitrogen deposition in the British Isles are reflected in
broad targeted chemical parameters in the common heathland lichen Cladonia
portentosa. A more detail analysis of alterations in the metabolic pathways in
Cladonia portentosa collected from different locations within the UK was
undertaken by applying the environmental metabolomics approach. Fourier
transform infrared spectroscopy (FTIR) and liquid chromatography mass
spectrometry (LC-MS) were applied in combination with principal component
analysis (PCA) and partial least squares regression analysis (PLSR). The latter
statistical method was used to correlate measured variables with modelled
atmospheric data including wet nitrogen deposition, nitrogen concentration and precipitation. While FTIR in combination with PCA and PLSR revealed signatures of broad metabolic classes, LC-MS in combination with PCA and PLSR allowed the identification of betaine lipids (BL) as potential biomarkers of nitrogen enrichment.
A compound tentatively identified as monoacylglycerol-(N,N,N trimethyl)-
homoserine (MGTS) showed the strongest positive relation to increasing wet
nitrogen deposition regimes and consequent phosphorus deficiency. In contrast, the structurally related phosphatidylcholine containing a C18:2 ester showed the opposite trend in natural populations of C. portentosa. Results obtained for C. portentosa collected from the N manipulation site Whim Moss indicated that ammonium is causal for the increase of two of the identified betaine lipids in natural populations in C. portentosa. Betaine lipids as well as the phosphatidylcholine biomarker could potentially be used to monitor nitrogen regimes and resulting phosphorus limitation on the lichen C. portentosa. The approach used for this study represented an effective integration of the complementary analytical techniques of FTIR and LC-MS in combination with multivariate statistical tools for environmental metabolomic studies.

Date of Award	6 Mar 2011
Original language	English
Awarding Institution	University of Edinburgh
Sponsors	UHI ARC Funding
Supervisor	Kenny Boyd (Supervisor), Stuart Gibb (Supervisor), Angela H. Squier (Supervisor) & Jorg Feldmann (Supervisor)