Heterosis or hybrid vigor is widespread in plants and animals. Although the molecular basis for heterosis has been extensively studied, metabolic and proteomic contributions to heterosis remain elusive. Here we report an integrative analysis of time-series metabolome and proteome data in maize (Zea mays) hybrids and their inbred parents. Many maize metabolites and proteins are diurnally regulated, and many of these show nonadditive abundance in the hybrids, including key enzymes and metabolites involved in carbon assimilation. Compared with robust trait heterosis, metabolic heterosis is relatively mild. Interestingly, most amino acids display negative mid-parent heterosis (MPH), i.e., having lower values than the average of the parents, while sugars, alcohols, and nucleoside metabolites show positive MPH. From the network perspective, metabolites in the photosynthetic pathway show positive MPH, whereas metabolites in the photorespiratory pathway show negative MPH, which corresponds to nonadditive protein abundance and enzyme activities of key enzymes in the respective pathways in the hybrids. Moreover, diurnally expressed proteins that are upregulated in the hybrids are enriched in photosynthesis-related gene-ontology terms. Hybrids may more effectively remove toxic metabolites generated during photorespiration, and thus maintain higher photosynthetic efficiency. These metabolic and proteomic resources provide unique insight into heterosis and its utilization for high yielding maize and other crop plants.

杂种优势或杂种优势广泛存在于动植物中。尽管已经广泛研究了杂种优势的分子基础，但是代谢和蛋白质组学对杂种优势的贡献仍然难以捉摸。在这里，我们报告了玉米杂种及其近交亲本中时间序列代谢组和蛋白质组数据的综合分析。玉米代谢产物和蛋白质的大部分是昼夜调节的，其中许多在杂种中显示出非累加的丰度，包括参与碳同化作用的关键酶和代谢产物。与高水平的特征杂种优势相比，代谢杂种优势相对较轻。有趣的是，大多数氨基酸显示出负的亲本杂种优势（MPH），而糖，醇和核苷中的代谢物则显示出阳性的MPH。从网络角度来看，光合途径中的代谢物显示出正MPH，而光呼吸途径中的代谢物则显示负MPH，这对应于杂合体各自途径中非加性蛋白质丰度和关键酶的酶活性。此外，在杂种中上调的节律蛋白富含光合作用相关的基因本体论术语。杂种可以更有效地去除光呼吸过程中产生的有毒代谢产物，从而保持较高的光合作用效率。这些代谢和蛋白质组学结果为杂种优势及其在高产玉米和其他农作物中的利用提供了新颖的见解。在杂种中上调的节律蛋白富含光合作用相关的基因本体论术语。杂种可以更有效地去除光呼吸过程中产生的有毒代谢产物，从而保持较高的光合作用效率。这些代谢和蛋白质组学结果为杂种优势及其在高产玉米和其他农作物中的利用提供了新颖的见解。在杂种中上调的节律蛋白富含光合作用相关的基因本体论术语。杂种可以更有效地去除光呼吸过程中产生的有毒代谢产物，从而保持较高的光合作用效率。这些代谢和蛋白质组学结果为杂种优势及其在高产玉米和其他农作物中的利用提供了新颖的见解。