Over-expression of poplar NAC15 gene enhances wood formation in transgenic tobacco

Abstract

BackgroundNAC (NAM/ATAF/CUC) family is one of the largest plant-specific 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.ResultsIn 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 most highly expressed genes in the stem among NAC family members. Thirdly, we conducted expression pattern analysis of NAC15 gene, and proved NAC15 gene was most highly expressed in the xylem. Moreover, we transferred NAC15 gene into tobacco and obtained 12 transgenic tobacco lines overexpressing the gene. And the relative content of hemicellulose, cellulose and lignin was determined to be higher in the transgenic plants than that in the control plants. It also showed darker staining in the culms of the transgenic plants with phloroglucinol staining, compared to the control plants. Furthermore, the relative expression level of a few lignin- and cellulose-related genes was significantly higher in the TLs than that in the CLs.ConclusionsThe overall results indicated that NAC15 gene is highly expressed in the xylem of poplar and plays an important role in wood formation in transgenic tobacco, which provides a foundation for the identification of wood-associated downstream genes and has significant implication in tree biology and biotechnology.