Tcherkez Guillaume, Gu Rard Florence, Gilard Fran Oise, Lamothe Marl Ne, Mauve Caroline, Gout Elisabeth, Bligny Richard
Institut de Biologie des Plantes, CNRS UMR8618, Université Paris-Sud, 91405 Orsay cedex, France.
Plateforme Métabolisme-Métabolome, IFR87, Batiment 630, Université Paris-Sud, 91405 Orsay cedex, France.
Funct Plant Biol. 2012 Dec;39(12):959-967. doi: 10.1071/FP12189.
Many horticultural and natural plant species have variegated leaves, that is, patchy leaves with green and non-green or white areas. Specific studies on the metabolism of variegated leaves are scarce and although white (non-green) areas have been assumed to play the role of a 'nitrogen store', there is no specific studies showing the analysis of nitrogenous metabolites and the dynamics of nitrogen assimilation. Here, we examined the metabolism of variegated leaves of Pelargonium×hortorum. We show that white areas have a larger N:C ratio, more amino acids, with a clear accumulation of arginine. Metabolomic analyses revealed clear differences in the chemical composition, suggesting contrasted metabolic commitments such as an enhancement of alkaloid biosynthesis in white areas. Using isotopic labelling followed by nuclear magnetic resonance or liquid chromatography/mass spectrometry, we further showed that in addition to glutamine, tyrosine and tryptophan, N metabolism forms ornithine in green area and huge amounts of arginine in white areas. Fine isotopic measurements with isotope ratio mass spectrometry indicated that white and green areas exchange nitrogenous molecules but nitrogen export from green areas is quantitatively much more important. The biological significance of the metabolic exchange between leaf areas is briefly discussed.
许多园艺植物和天然植物物种都有杂色叶，即带有绿色和非绿色或白色区域的斑驳叶片。关于杂色叶代谢的具体研究很少，尽管白色（非绿色）区域被认为起到了“氮储存”的作用，但尚无具体研究表明对含氮代谢物的分析以及氮同化的动态变化。在此，我们研究了天竺葵杂色叶的代谢情况。我们发现白色区域具有更高的氮碳比，含有更多氨基酸，其中精氨酸明显积累。代谢组学分析揭示了化学成分上的明显差异，表明存在不同的代谢倾向，比如白色区域生物碱生物合成增强。通过同位素标记，随后进行核磁共振或液相色谱/质谱分析，我们进一步表明，除了谷氨酰胺、酪氨酸和色氨酸外，氮代谢在绿色区域形成鸟氨酸，在白色区域形成大量精氨酸。利用同位素比率质谱仪进行的精细同位素测量表明，白色和绿色区域会交换含氮分子，但绿色区域的氮输出在数量上要重要得多。我们简要讨论了叶区域间代谢交换的生物学意义。
