作者单位:Michigan State Univ, Mass Spectrometry & Metabol Core Facil, E Lansing, MI 48824 USA[1]Univ Michigan, Dept Mol Cellular & Dev Biol, Ann Arbor, MI 48109 USA[2]Wageningen Univ & Res, Business Unit Biosci, Wageningen Plant Res, Droevendaalsesteeg 1, NL-6708 PB Wageningen, Netherlands[3]