Characterization of the phytochelatins and their derivatives in rice exposed to cadmium based on high-performance liquid chromatography coupled with data-dependent hybrid linear ion trap orbitrap mass spectrometry.

Rationale: The identification and quantification of phytochelatins (PCs) and their derivatives are important to understand their roles in plant growth and development. A method couplling high-performance liquid chromatography with hybrid linear ion trap Orbitrap mass spectrometry (HPLC-LTQ/Orbitrap) was developed to screen PCs that have the same characteristic product ions. This approach was used for the fragmentation pattern analysis of glutathione (GSH) and PC standards, which allowed identification of the fragmentation pathways of their derivatives isolated from rice roots, stems and leaves.

Methods: In this study, we developed a method to detect and identify PCs and their derivatives in rice based on HPLC/LTQ-Orbitrap. Spectrum interpretation and MS/MS fragmentation patterns of PCs provide sufficient information to discover the novel PC derivatives. This approach includes precursor ion scan and product ion scan to detect and character the novel PC derivatives.

Results: Based on HCD-MS/MS fragmentation patterns, four PCs and 18 PC derivatives were identified. Among them, seven PC derivatives, i.e., iso-PC2 (Asn), iso-PC3 (Asn), iso-PC2 (Cys), des-γGlu-iso-PC3 (Ser), des-Cys-iso-PC2 (Glu), des-Cys-iso-PC3 (Glu) and des-Cys-iso-PC4 (Glu), have not been previously reported. This method was validated by profiling GSH, PCs and PC derivatives in rice. Preliminary results revealed that PCs and their derivatives, except GSH, are markedly induced by Cd treatment.

Conclusions: The HPLC/LTQ-Orbitrap method was successfully developed for the identification of PCs and their derivatives. The C-terminal linked to Gly is replaced with Glu, Ser, Asn, Gln or Cys, thereby creating a family of chemicals that share several structural properties. This technique could be particularly useful for investigators studying plant metabolomics. Copyright © 2016 John Wiley & Sons, Ltd.