Rapid glycosyl‐inositol‐phospho‐ceramide fingerprint from filamentous fungal pathogens using the MALDI Biotyper Sirius system

Abstract

Glycosyl-inositol-phospho-ceramides (GIPCs) or glycosylphosphatidylinositolanchored fungal polysaccharides are known to be major lipids in plant and fungal plasma membranes and to play an important role in stress adaption. However, their analysis remains challenging due to the several steps involved for their extractions and purifications prior to mass spectrometric analysis. To address this challenge, we developed a rapid and sensitive method to identify GIPCs from the four common fungal plant pathogens Botrytis cinerea, Fusarium graminearium, Neurospora crassa and Ustilago maydis. Methods: Fungal plant pathogens were cultured, harvested, heat-inactivated and washed three times with double-distilled water. Intact fungi were deposited on a matrix-assisted laser desorption ionization (MALDI) target plate, mixed with the matrix consisting of a 9:1 mixture of 2,5-dihydroxybenzoic acid and 2-hydroxy-5-methoxybenzoic acid solubilized at 10 mg/mL in chloroform-methanol (9:1 v/v) and analyzed using a Bruker MALDI Biotyper Sirius system in the linear negative ion mode. Mass spectra were acquired from m/z 700 to 2000. Results: MALDI time-of-flight (TOF) mass spectrometric analysis of cultured fungi showed clear signature of GIPCs in B. cinerea, F. graminearium, N. crassa and U. maydis. Conclusions: We have demonstrated that routine MALDI-TOF in the linear negative ion mode combined with an apolar solvent system to solubilize the matrix is applicable to the detection of filamentous fungal GIPCs.