Zhang Yang, Liu Yingying, Wang Xueying, Wang Ruiqi, Chen Xuebing, Wang Shuang, Wei Hairong, Wei Zhigang
Engineering Research Center of Agricultural Microbiology Technology, Ministry of Education, Heilongjiang University, Harbin, China.
State Key Laboratory of Tree Genetics and Breeding, Northeast Forestry University, Harbin, China.
Front Plant Sci. 2022 Jun 28;13:835035. doi: 10.3389/fpls.2022.835035. eCollection 2022.
WUSCHEL-related homeobox (WOX) genes are plant-specific transcription factors (TFs) involved in multiple processes of plant development. However, there have hitherto no studies on the WOX TFs involved in secondary cell wall (SCW) formation been reported. In this study, we identified a WOX gene, , which was predominantly expressed in SCW, and then characterized its functions through generating overexpression poplar transgenic lines; these lines exhibited not only significantly enhanced growth potential, but also remarkably increased SCW thicknesses, fiber lengths, and lignin and hemicellulose contents. However, no obvious change in cellulose content was observed. We revealed that directly activated its target genes through binding to two -elements, ATTGATTG and TTAATSS, in their promoter regions. The fact that responded to the exogenous GAs implies that it is responsive to GA homeostasis caused by GA inactivation and activation genes (e.g., , , and ), which were regulated by PtrWOX13A directly or indirectly. Since the master switch gene of SCW formation, , and lignin biosynthesis regulator, MYB28, significantly increased in transgenic lines, we proposed that , as a higher hierarchy TF, participated in SCW formation through controlling the genes that are components of the known hierarchical transcription regulation network of poplar SCW formation, and simultaneously triggering a gibberellin-mediated signaling cascade. The discovery of predominantly expressed in SCW and its regulatory functions in the poplar wood formation has important implications for improving the wood quality of trees genetic engineering.
WUSCHEL相关同源异型框（WOX）基因是植物特有的转录因子，参与植物发育的多个过程。然而，迄今为止，尚未有关于参与次生细胞壁（SCW）形成的WOX转录因子的研究报道。在本研究中，我们鉴定了一个主要在SCW中表达的WOX基因，然后通过构建过表达杨树转基因株系来表征其功能；这些株系不仅表现出显著增强的生长潜力，而且SCW厚度、纤维长度以及木质素和半纤维素含量也显著增加。然而，未观察到纤维素含量有明显变化。我们发现该基因通过与靶基因启动子区域的两个元件ATTGATTG和TTAATSS结合，直接激活其靶基因。该基因对外源赤霉素（GA）有响应，这意味着它对由GA失活和激活基因（如某些基因）引起的GA稳态有响应，而这些基因受PtrWOX13A直接或间接调控。由于SCW形成的主控开关基因以及木质素生物合成调节因子MYB28在该转基因株系中显著增加，我们提出，作为一个更高层次的转录因子，该基因通过控制杨树SCW形成已知层次转录调控网络中的组成基因，同时触发赤霉素介导的信号级联反应，参与SCW的形成。该基因在SCW中大量表达及其在杨树木材形成中的调控功能的发现，对通过基因工程提高树木木材质量具有重要意义。
