BACKGROUND NAC (NAM/ATAF/CUC) is one of the largest plant-specific transcription factor (TF) families known to play significant roles in wood formation. Acting as master gene regulators, a few NAC genes can activate secondary wall biosynthesis during wood formation in woody plants. RESULTS In the present study, firstly, we screened 110 differentially expressed NAC genes in the leaves, stems, and roots of di-haploid Populus simonii×P. nigra by RNA-Seq. Then we identified a nucleus-targeted gene, NAC15 gene, which was one of the highly expressed genes in the stem among 110 NAC family members. Thirdly, we conducted expression pattern analysis of NAC15 gene, and observed NAC15 gene was most highly expressed in the xylem by RT-qPCR. Moreover, we transferred NAC15 gene into tobacco and obtained 12 transgenic lines overexpressing NAC15 gene (TLs). And the relative higher content of hemicellulose, cellulose and lignin was observed in the TLs compared to the control lines containing empty vector (CLs). It also showed darker staining in the culms of the TLs with phloroglucinol staining, compared to the CLs. Furthermore, the relative expression level of a few lignin- and cellulose-related genes was significantly higher in the TLs than that in the CLs. CONCLUSIONS The overall results indicated that NAC15 gene is highly expressed in the xylem of poplar and may be a potential candidate gene playing an important role in wood formation in transgenic tobacco.

中文翻译：

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杨树NAC15基因的过表达增强了转基因烟草中的木材形成。

背景技术NAC（NAM / ATAF / CUC）是最大的植物特异性转录因子（TF）家族之一，已知其在木材形成中起重要作用。作为主要的基因调节剂，一些NAC基因可以在木本植物的木材形成过程中激活次生壁的生物合成。结果本研究首先在双单倍体胡杨×P的叶片，茎和根中筛选了110个差异表达的NAC基因。黑色-RNA测序 然后，我们鉴定了一个以核为靶向的基因NAC15基因，它是110个NAC家族成员中茎中高表达的基因之一。第三，我们对NAC15基因的表达模式进行了分析，通过RT-qPCR观察到NAC15基因在木质部中的表达最高。此外，我们将NAC15基因转移到烟草中，获得了12个过表达NAC15基因（TLs）的转基因品系。与含有空载体（CL）的对照品系相比，TL中的半纤维素，纤维素和木质素含量相对较高。与间苯二酚相比，在间苯三酚染色的TLs的茎杆上也显示出较深的染色。此外，一些木质素和纤维素相关基因的相对表达水平在TL中明显高于在CL中。结论总的结果表明，NAC15基因在杨的木质部中高度表达，并且可能是潜在的候选基因，在转基因烟草的木材形成中起重要作用。与CL相比。此外，一些木质素和纤维素相关基因的相对表达水平在TL中明显高于在CL中。结论总的结果表明，NAC15基因在杨的木质部中高度表达，并且可能是潜在的候选基因，在转基因烟草的木材形成中起重要作用。与CL相比。此外，一些木质素和纤维素相关基因的相对表达水平在TL中明显高于在CL中。结论总的结果表明，NAC15基因在杨的木质部中高度表达，并且可能是潜在的候选基因，在转基因烟草的木材形成中起重要作用。