National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, PR China.
Proteomics. 2009 Dec;9(24):5455-70. doi: 10.1002/pmic.200900092.
A spontaneous sweet orange (Citrus sinenesis [L.] Osbeck) mutant 'Hong Anliu' is of high value due to lycopene accumulation in the pulp. In this study, we analyzed the proteomic alterations in the pulp of 'Hong Anliu' versus its wild type (WT) at four maturing stages by using 2-DE combined with MALDI-TOF-TOF MS. Among the 74 differentially expressed proteins identified, the majority are predicted to be involved in stress response, carbohydrate/energy metabolism and regulation, or protein fate, modification and degradation. Particularly, expression levels of six anti-oxidative enzymes were altered by the mutation; and assays of their respective enzymatic activities indicated an enhanced level of oxidative stress in 'Hong Anliu', implying a regulatory role of oxidative stress on carotenogenesis. This conclusion was further confirmed by our observation that treatment of fruit pulps with tert-butylhydroperoxide (a ROS progenitor) induced lycopene accumulation in 'Hong Anliu' only. Gene expression showed that genes predicted to function upstream of lycopene biosynthesis were generally upregulated in juice sacs, but downregulated in segment membranes in both 'Hong Anliu' and its WT. The result suggests an important role of post-transcriptional regulation on carotenogenesis since lycopene was induced in 'Hong Anliu' but not WT. The result also implies that carotenogenesis in juice sacs and segment membranes of citrus fruits may be regulated by different mechanisms.
自发突变甜橙（Citrus sinenesis [L.] Osbeck）品种‘红安流’由于果肉中番茄红素的积累而具有很高的价值。在本研究中，我们通过 2-DE 结合 MALDI-TOF-TOF MS 分析了四个成熟阶段‘红安流’与其野生型（WT）果肉中的蛋白质组变化。在鉴定的 74 个差异表达蛋白中，大多数被预测参与应激反应、碳水化合物/能量代谢和调控，或蛋白质命运、修饰和降解。特别是，突变导致六种抗氧化酶的表达水平发生改变；并且它们各自的酶活性测定表明‘红安流’中氧化应激水平增强，表明氧化应激对类胡萝卜素生物合成的调控作用。这一结论进一步得到了我们的观察结果的证实，即用叔丁基过氧化物（ROS 前体）处理果肉仅诱导‘红安流’中番茄红素的积累。基因表达表明，在汁囊预测具有类胡萝卜素生物合成上游功能的基因普遍上调，但在‘红安流’及其 WT 的隔膜中下调。这一结果表明，由于在‘红安流’中诱导了番茄红素而不是 WT，因此在后转录调控对类胡萝卜素生物合成起着重要作用。这一结果还表明，柑橘果实汁囊和隔膜中的类胡萝卜素生物合成可能受到不同机制的调控。
