State Key Laboratory of Tree Genetics and Breeding, Northeast Forestry University, Heilongjiang Harbin, 150040, P.R. China.
School of Forest Resource and Environmental Science, Michigan Technological University, Houghton, MI, 49931, USA.
Sci Rep. 2017 Mar 3;7(1):42. doi: 10.1038/s41598-017-00093-z.
Wood formation is a biological process during which the most abundant lignocellulosic biomass on earth is produced. Although a number of transcription factors have been linked to the regulation of wood formation process, none of them has been demonstrated to be a higher hierarchical regulator that coordinately regulates secondary wall biosynthesis genes. Here, we identified a Populus gene, PsnSHN2, a counterpart of the Arabidopsis AP2/ERF type transcription factor, SHINE2. PsnSHN2 is predominantly expressed in xylem tissues and acted evidently as a high hierarchical transcriptional activator. Overexpression of PsnSHN2 in tobacco significantly altered the expression of both transcription factors and biosynthesis genes involved in secondary wall formation, leading to the thickened secondary walls and the changed cell wall composition. The most significant changes occurred in the contents of cellulose and hemicellulose that increased 37% and 28%, respectively, whereas the content of lignin that decreased 34%. Furthermore, PsnSHN2 activated or repressed the promoter activities of transcription factors involved in secondary wall biosynthesis and bound to five cis-acting elements enriched in the promoter regions of these transcription factors. Taken together, our results suggest PsnSHN2 coordinately regulate secondary wall formation through selective up/down-regulation of its downstream transcription factors that control secondary wall formation.
木材的形成是一个生物过程，在此过程中产生了地球上最丰富的木质纤维素生物质。虽然已经有许多转录因子与木材形成过程的调节有关，但没有一个被证明是一个更高层次的调节因子，可以协调调节次生壁生物合成基因。在这里，我们鉴定了一个杨树基因 PsnSHN2，它是拟南芥 AP2/ERF 型转录因子 SHINE2 的同源物。PsnSHN2 在木质部组织中表达丰富，明显作为一个高层次的转录激活因子发挥作用。在烟草中过表达 PsnSHN2 显著改变了参与次生壁形成的转录因子和生物合成基因的表达，导致次生壁增厚和细胞壁组成的改变。最显著的变化发生在纤维素和半纤维素的含量上，分别增加了 37%和 28%，而木质素的含量则减少了 34%。此外，PsnSHN2 激活或抑制了参与次生壁生物合成的转录因子的启动子活性，并与这些转录因子启动子区域中富含的五个顺式作用元件结合。总之，我们的研究结果表明，PsnSHN2 通过选择性地上调/下调其下游转录因子来协调调节次生壁的形成，从而控制次生壁的形成。
