Phosphorylation of LTF1, A MYB Transcription Factor in Populus, Acts as a Sensory Switch Regulating Lignin Biosynthesis in Wood Cells

First author: Jinshan Gui; Affiliations: CAS Center for Excellence in Molecular Plant Sciences (中科院分子植物科学卓越创新中心): Shanghai, China

Corresponding author: Laigeng Li

Lignin is specifically deposited in plant secondary cell walls and initiation of lignin biosynthesis is regulated by a variety of developmental and environmental signals. However, the mechanism governing the regulation of lignin biosynthesis remains to be elucidated. Here, we identified a lignin biosynthesis associated transcription factor (LTF) from Populus, LTF1, which binds to the promoter of 4-coumarate-CoA ligase (4CL), a key lignin biosynthetic gene. We showed that LTF1 in its unphosphorylated state functions as a regulator to restrain lignin biosynthesis. When LTF1 becomes phosphorylated by PdMPK6 in response to external stimuli such as wounding, it underwent degradation through a proteasome pathway, resulting in activation of lignification. Expression of the LTF1 phosphorylation-null mutation led to stable LTF1 accumulation and persistent attenuation of lignification in wood cells. The study reveals a mechanism where LTF1 phosphorylation acts as a sensory switch to regulate lignin biosynthesis in response to environmental stimuli. The discovery of novel modulators and mechanisms to modify lignin biosynthesis has important implications for improving the utilization of cell wall biomass.

木质素在植物的次生细胞壁中特异性沉积，木质素合成的起始受到多个发育和环境信号的调控。然而，木质素合成调控的分子机制还有待进一步探索。本文中，作者在杨树中鉴定到了一个木质素生物合成相关的转录因子LTF1，该转录因子能够结合到4-香豆酸-CoA连接酶4CL的启动子区，而4CL是木质素生物合成的一个关键基因。作者的研究显示LTF1处于未磷酸化状态时，会抑制木质素的生物合成。当植物受到诸如创伤等外部刺激后，LTF1会被PdMPK6磷酸化，进一步通过蛋白酶体途径被降解，从而激活木质化。LTF1磷酸化突变体中LTF1能够稳定积累，同时木质化细胞中的木质化程度持续衰减。本文的研究揭示了LTF1磷酸化作为一个敏感的开关调控植物响应于环境刺激时的木质素生物合成。本文发现的新的木质素生物合成调控机制对于提高细胞壁生物量的利用具有非常重要的意义。

通讯：李来庚(http://sourcedb.sibs.cas.cn/zw/rck/200906/t20090629_1856166.html)

个人简介：1982年，中南林学院，学士；1985年，中南林学院，硕士；1997年，Michigan Technological University，博士。

研究方向： 1. 植物细胞壁生物合成的分子生物学与基因工程研究； 2. 木质部细胞分化的分子调控机理研究； 3. 木质纤维生物质合成的功能基因组学研究； 4. 有效利用木质纤维生物质能源的技术研究。

doi: https://doi.org/10.1016/j.molp.2019.05.008

Journal: Molecular Plant

Published date: May 27, 2019