Methionine-SMM Analysis Using LCMS in MRM Mode

Ilana Rogachev, Department of Plant Sciences, Weizmann Institute of Science, Rehovot, Israel
Hagai Cahen, Department Of Plant Sciences, Weizmann Institute Of Science, Rehovot, Laboratory of Plant Science, Migal - Galilee Technology Center, Kiryat Shmona Israel
Ira Panizel, Department Of Plant Sciences, Weizmann Institute Of Science, Rehovot, Israel
Liron Feldberg, Department Of Plant Sciences, Weizmann Institute Of Science, Rehovot, Israel
Yonghui Dong, Department Of Plant Sciences, Weizmann Institute Of Science, Rehovot, Israel
Rachel Amir, Laboratory Of Plant Science, Migal - Galilee Technology Center, Kiryat Shmona, Israel
Asaph Aharoni, Department Of Plant Sciences, Weizmann Institute Of Science, Rehovot, Israel

S-Methylmethionine (SMM), a unique compound found solely in plants, functions as an intermediate to support methionine synthesis in seeds. We aimed at investigating the relative contribution of SMM to methionine metabolism in Arabidopsis seeds during development. We have generated transgenic plants with lower expression of methionine main regulatory enzyme CYSTATHIONINE γ-SYNTHASE (AtCGS). Then, we fed whole WT and transgenic plants with isotope-labelled ¹³C methionine to monitor the levels of Methionine, ¹³C-Methionine, SMM and ¹³C-SMM in the vegetative and reproductive tissues. To this end, we set up an analytical method for simultaneous analysis of these compounds in tissue extracts. The compounds were separated on mixed mode Obelisc-N column, and non-labeled / labeled molecules ratios were measured using Triple Quad Mass Spectrometer in MRM mode. Isotope-labeled feeding experiments provided an evidence for higher production of ¹³C-SMM in leaves of transgenic plants together with greater ability to re-convert transported ¹³C-SMM back to ¹³C-methionine in their developing seeds.