BACKGROUND The cytochrome P450s (CYP450s) as the largest enzyme family of plant metabolism participate in various physiological processes, whereas no study has demonstrated interest in comprehensive comparison of the genes in wheat and maize. Genome-wide survey, characterization and comparison of wheat and maize CYP450 gene superfamily are useful for genetic manipulation of the Gramineae crops. RESULTS In total, 1285 and 263 full-length CYP450s were identified in wheat and maize, respectively. According to standard nomenclature, wheat CYP450s (TaCYP450s) were categorized into 45 families, while maize CYP450s (ZmCYP450s) into 43 families. A comprehensive analysis of wheat and maize CYP450s, involved in functional domains, conserved motifs, phylogeny, gene structures, chromosome locations and duplicated events was performed. The result showed that each family/subfamily in both species exhibited characteristic features, suggesting their phylogenetic relationship and the potential divergence in their functions. Functional divergence analysis at the amino acid level of representative clans CYP51, CYP74 and CYP97 in wheat, maize and rice identified some critical amino acid sites that are responsible for functional divergence of a gene family. Expression profiles of Ta-, ZmCYP450s were investigated using RNA-seq data, which contribute to infer the potential functions of the genes during development and stress responses. We found in both species CYP450s had preferential expression in specific tissues, and many tissue-specific genes were identified. Under water-deficit condition, 82 and 39 significantly differentially expressed CYP450s were respectively detected in wheat and maize. These genes may have some roles in protecting plants against drought damage. Thereinto, fourteen CYP450s were selected to validate their expression level through qRT-PCR. To further elucidating molecular mechanisms of CYP450 action, gene co-expression network was constructed. In total, 477 TaCYP450s were distributed in 22 co-expression modules, and some co-expressed genes that likely take part in the same biochemical pathway were identified. For instance, the expression of TaCYP74A98_4D was highly correlated with TaLOX9, TaLOX36, TaLOX39, TaLOX44 and TaOPR8, and all of them may be involved in jasmonate (JA) biosynthesis. TaCYP73A201_3A showed coexpression with TaPAL1.25, TaCCoAOMT1.2, TaCOMT.1, TaCCR1.6 and TaLAC5, which probably act in the wheat stem and/or root lignin synthesis pathway. CONCLUSION Our study first established systematic information about evolutionary relationship, expression pattern and function characterization of CYP450s in wheat and maize.

中文翻译：

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小麦和玉米中细胞色素P450基因超家族的比较功能基因组学分析。

背景技术细胞色素P450（CYP450s）作为植物代谢的最大酶家族，参与各种生理过程，而没有研究表明对小麦和玉米基因的全面比较感兴趣。小麦和玉米CYP450基因超家族的全基因组调查，鉴定和比较可用于禾本科作物的遗传操作。结果总共在小麦和玉米中鉴定出1285和263个全长CYP450。根据标准命名法，小麦CYP450（TaCYP450s）分为45个科，而玉米CYP450（ZmCYP450s）分为43个科。对涉及功能域，保守基序，系统发育，基因结构，染色体位置和重复事件的小麦和玉米CYP450进行了全面分析。结果表明，两个物种的每个科/亚科均表现出特征性特征，表明了它们的系统发育关系和功能上的潜在差异。在小麦，玉米和水稻中具有代表性的宗族CYP51，CYP74和CYP97的氨基酸水平上的功能差异分析确定了一些关键氨基酸位点，这些位点负责基因家族的功能差异。使用RNA-seq数据研究了Ta-，ZmCYP450的表达谱，这有助于推断基因在发育和应激反应中的潜在功能。我们发现在这两个物种中，CYP450s在特定组织中均具有优先表达，并且已鉴定出许多组织特异性基因。在缺水的情况下 在小麦和玉米中分别检测到82和39个显着差异表达的CYP450。这些基因可能在保护植物免受干旱损害方面具有某些作用。其中，选择14种CYP450通过qRT-PCR验证其表达水平。为了进一步阐明CYP450作用的分子机制，构建了基因共表达网络。共有477个TaCYP450s分布在22个共表达模块中，并鉴定了一些可能参与同一生化途径的共表达基因。例如，TaCYP74A98_4D的表达与TaLOX9，TaLOX36，TaLOX39，TaLOX44和TaOPR8高度相关，它们都可能参与了茉莉酸（JA）的生物合成。TaCYP73A201_3A与TaPAL1.25，TaCCoAOMT1.2，TaCOMT.1，TaCCR1.6和TaLAC5共表达，可能在小麦茎和/或根木质素合成途径中起作用。结论我们的研究首先建立了有关CYP450在小麦和玉米中的进化关系，表达模式和功能特性的系统信息。