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Quantification of plant surface metabolites by matrix‐assisted laser desorption–ionization mass spectrometry imaging: glucosinolates on A rabidopsis thaliana leaves
Author(s) -
Shroff Rohit,
Schramm Katharina,
Jeschke Verena,
Nemes Peter,
Vertes Akos,
Gershenzon Jonathan,
Svatoš Aleš
Publication year - 2015
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.12760
Subject(s) - glucosinolate , mass spectrometry , chemistry , matrix assisted laser desorption/ionization , desorption , chromatography , arabidopsis thaliana , botany , analytical chemistry (journal) , biochemistry , biology , organic chemistry , brassica , adsorption , gene , mutant
Summary The localization of metabolites on plant surfaces has been problematic because of the limitations of current methodologies. Attempts to localize glucosinolates, the sulfur‐rich defense compounds of the order B rassicales, on leaf surfaces have given many contradictory results depending on the method employed. Here we developed a matrix‐assisted laser desorption–ionization ( MALDI ) mass spectrometry protocol to detect surface glucosinolates on A rabidopsis thaliana leaves by applying the MALDI matrix through sublimation. Quantification was accomplished by spotting glucosinolate standards directly on the leaf surface. The A . thaliana leaf surface was found to contain approximately 15 nmol of total glucosinolate per leaf with about 50 pmol mm −2 on abaxial (bottom) surfaces and 15–30 times less on adaxial (top) surfaces. Of the major compounds detected, 4‐methylsulfinylbutylglucosinolate, indol‐3‐ylmethylglucosinolate, and 8‐methylsulfinyloctylglucosinolate were also major components of the leaf interior, but the second most abundant glucosinolate on the surface, 4‐methylthiobutylglucosinolate, was only a trace component of the interior. Distribution on the surface was relatively uniform in contrast to the interior, where glucosinolates were distributed more abundantly in the midrib and periphery than the rest of the leaf. These results were confirmed by two other mass spectrometry‐based techniques, laser ablation electrospray ionization and liquid extraction surface analysis. The concentrations of glucosinolates on A . thaliana leaf surfaces were found to be sufficient to attract the specialist feeding lepidopterans P lutella xylostella and P ieris rapae for oviposition. The methods employed here should be easily applied to other plant species and metabolites.