Metabolite Profiling of Low-P Tolerant and Low-P Sensitive Maize Genotypes under Phosphorus Starvation and Restoration Conditions

BackgroundMaize (Zea mays L.) is one of the most widely cultivated crop plants. Unavoidable economic and environmental problems associated with the excessive use of phosphatic fertilizers demands its better management. The solution lies in improving the phosphorus (P) use efficiency to sustain productivity even at low P levels. Untargeted metabolomic profiling of contrasting genotypes provides a snap shot of whole metabolome which differs under specific conditions. This information provides an understanding of the mechanisms underlying tolerance to P stress and the approach for increasing P-use-efficiency.Methodology/Principal FindingsA comparative metabolite-profiling approach based on gas chromatography-mass spectrometry (GC/MS) was applied to investigate the effect of P starvation and its restoration in low-P sensitive (HM-4) and low-P tolerant (PEHM-2) maize genotypes. A comparison of the metabolite profiles of contrasting genotypes in response to P-deficiency revealed distinct differences among low-P sensitive and tolerant genotypes. Another set of these genotypes were grown under P-restoration condition and sampled at different time intervals (3, 5 and 10 days) to investigate if the changes in metabolite profile under P-deficiency was restored. Significant variations in the metabolite pools of these genotypes were observed under P-deficiency which were genotype specific. Out of 180 distinct analytes, 91 were identified. Phosphorus-starvation resulted in accumulation of di- and trisaccharides and metabolites of ammonium metabolism, specifically in leaves, but decreased the levels of phosphate-containing metabolites and organic acids. A sharp increase in the concentrations of glutamine, asparagine, serine and glycine was observed in both shoots and roots under low-P condition.ConclusionThe new insights generated on the maize metabolome in resposne to P-starvation and restoration would be useful towards improvement of the P-use efficiency in maize.背景 玉米（Zea mays L.）是全球种植范围最广的作物之一。过量施用磷肥引发的经济与环境问题亟需优化磷肥管理方案。提升磷（P）利用效率，可在低磷水平下维持作物生产力，是解决上述问题的核心路径。对差异基因型开展非靶向代谢组学分析（untargeted metabolomic profiling），可获取特定条件下全代谢组的快照信息，此类信息有助于解析磷胁迫耐受的内在机制，并为提升磷利用效率提供理论依据。 材料与方法/主要结果 本研究采用基于气相色谱-质谱联用（gas chromatography-mass spectrometry, GC/MS）的比较代谢组学方法，探究磷饥饿胁迫及其恢复处理对低磷敏感型（HM-4）和低磷耐受型（PEHM-2）玉米基因型的影响。对磷胁迫下差异基因型的代谢谱进行比较分析，结果显示低磷敏感与耐受型基因型间存在显著代谢特征差异。本研究同时设置磷恢复培养组，将上述基因型种植于该条件下，并分别在处理第3、5、10天取样，以验证磷胁迫诱导的代谢谱变化是否可被恢复。结果表明，不同基因型的代谢物库在磷胁迫下存在显著变化，且该变化具有基因型特异性。本研究共检测到180种明确的代谢物，其中91种得到鉴定。磷饥饿胁迫可导致叶片中二糖、三糖及铵代谢相关代谢物的积累，但降低了含磷代谢物与有机酸的含量；此外，低磷条件下玉米地上部与根部的谷氨酰胺、天冬酰胺、丝氨酸及甘氨酸浓度均出现显著升高。 结论 本研究针对玉米在磷饥饿及恢复处理下的代谢组特征所获得的全新认知，可为提升玉米磷利用效率提供重要理论支撑。