Use of Paper Spray Mass Spectrometry to Detect Phytochelatins in Golden Flaxseed Roots after Contact with Arsenate and Selenite

Phytochelatins (PCs) are thiol-rich peptides essential for detoxifying toxic metals such as arsenic (As) and selenium (Se) which compete for sulfhydryl groups involved in detoxification within plant cells. This study employed paper-spray mass spectrometry (PS-MS) to detect glutathione (GSH), free phytochelatins (PC2 and PC3), and their metal complexes (As-PC3 and Se-PC2) in golden flaxseed roots. Plants were exposed to arsenate (0 and 50 μmol L–1) and selenite (5 and 25 μmol L–1). Root tissues were cryogenically ground and extracted with formic acid. Inductively coupled plasma mass spectrometry (ICP-MS) quantified total As and Se, while PS-MS allowed direct detection of thiol-containing compounds and their complexes. Fragmentation patterns confirmed the presence of GSH, reduced PC2, reduced PC3, Se-PC2, and As-PC3. Selenium exposure enhanced GSH biosynthesis, whereas arsenic induced phytochelatins production, suggesting a response to metalloid stress. The results highlight the key role of free PCs and their metal-bound forms in detoxification and demonstrate the utility of PS-MS and tandem MS in profiling metal-thiol complexes in plant tissues. The findings provide new insights into metal detoxification pathways and contribute to a deeper understanding of plant tolerance mechanisms in contaminated environments.