Lignin is essential for the characteristics and quality of timber. Nitrogen has significant effects on lignin contents in plants. Nitrogen has been found to affect wood quality in plantations and lignin content in plants. Caffeoyl-CoA 3-O-methyltransferase (CCoAOMT) is an important methyltransferase in lignin biosynthesis. However, the classification of woody plant CCoAOMT gene family members and the regulation mechanism of nitrogen are not clear. Bioinformatics methods were used to predict the members, classification, and transcriptional distribution of the CCoAOMT gene family in Populus trichocarpa. The results showed that there were five PtCCoAOMTs identified, and they could be divided into three sub-groups according to their structural and phylogenetic features. The results of tissue expression specificity analysis showed that: PtCCoAOMT1 was highly expressed in roots and internodes; PtCCoAOMT2 was highly expressed in roots, nodes, and internodes, PtCCoAOMT3 was highly expressed in stems; PtCCoAOMT4 was highly expressed in young leaves, and, PtCCoAOMT5 was highly expressed in roots. Different forms and concentrations of nitrogen had varying effects on the expression patterns of genes in different plant tissue types. The results of real-time PCR showed that the expression levels of PtCCoAOMT1 and PtCCoAOMT2 in stems increased significantly under different forms of nitrogen. PtCCoAOMT3 and PtCCoAOMT4 were induced by nitrate nitrogen in upper stems and lower leaves, respectively. PtCCoAOMT4 and PtCCoAOMT5 were induced by different concentrations of nitrate nitrogen in lower stems and roots, respectively. These results could provide valuable information for revealing the differences between functions and expression patterns of the various CCoAOMT gene family members under different forms and concentrations of exogenous nitrogen in poplar.

木质素对于木材的特性和质量至关重要。氮对植物中木质素的含量有显着影响。已发现氮会影响种植园的木材质量和植物中的木质素含量。咖啡酰-CoA 3-O-甲基转移酶（CCoAOMT）是木质素生物合成中重要的甲基转移酶。然而，木本植物CCoAOMT基因家族成员的分类及氮的调控机制尚不明确。采用生物信息学方法预测毛果杨CCoAOMT基因家族的成员、分类和转录分布。结果表明，有 5 个PtCCoAOMTs根据其结构和系统发育特征，它们可分为三个亚组。组织表达特异性分析结果表明：PtCCoAOMT1在根和节间高表达；PtCCoAOMT2在根、节和节间高表达，PtCCoAOMT3在茎中高表达；PtCCoAOMT4在幼叶中高表达，PtCCoAOMT5在根中高表达。不同形式和浓度的氮对不同植物组织类型中基因的表达模式有不同的影响。实时荧光定量 PCR 结果显示PtCCoAOMT1和PtCCoAOMT2的表达水平在不同形式的氮下，茎中显着增加。PtCCoAOMT3和PtCCoAOMT4分别由上部茎和下部叶中的硝酸盐氮诱导。PtCCoAOMT4和PtCCoAOMT5分别由下部茎和根中不同浓度的硝酸盐氮诱导。这些结果可为揭示杨树不同形式和浓度外源氮作用下不同CCoAOMT基因家族成员的功能和表达模式之间的差异提供有价值的信息。