背景+问题：Somatic embryogenesis (SE) are widely used for studying the mechanisms of embryo development. However, little is known about the underlying mechanisms especially in woody plants. Previous studies have revealed a SE system has been well-established for Cunninghamia lanceolata, but in a genotype-dependent manner which limits its application in practice.

主要发现：Here, we found that phytosulfokine (PSK), a plant peptide hormone, can not only increase SE efficiency, but also establish SE in those recalcitrant genotypes of C. lanceolata. 

结果1-PSK抑制体胚诱导早期的ROS爆发：PEM browning and determination of hydrogen peroxide (H₂O2) content by dichlorofluorescein (DCF) staining indicated that a reactive oxygen species (ROS) burst occurred rapidly after PEMs were transferred to the SE induction medium. Transcriptome analysis and qRT-PCR validation showed that PSK treatment helped to maintain ROS homeostasis by decreasing the activity of PRXs in the early SE induction. 

结果2-PSK促进体胚诱导早期WOX2的表达：This appropriate redox microenvironment medicated by PSK treatment might be helpful for expression induction of SE related genes like WOX2 in the early SE induction.

结果3-PSK部分通过ROS促进体胚发生： Further analyses suggested that PSK promotes C. lanceolata SE induction partially through the decreasing of H₂O2 levels which is necessary but not sufficient for SE induction in recalcitrant genotypes of C. lanceolata. 

结果4-异源过表达ClPSK：Furthermore, heterologous overexpression of ClPSK in Arabidopsis led to an enhanced SE induction and resistance to H₂O2 stress. 

结论：Taken together, our study identifies a biological function for the plant peptide hormone PSK, extends our knowledge about SE in woody trees and provides a valuable tool for establishing an efficient and genotype-independent SE system in C. lanceolata and other coniferous trees.

体细胞胚胎发生（体胚发生）被广泛用于胚胎发育的机理研究。但是，有关木本植物的体胚发生机理研究却所知甚少。先前已经有报道成功在杉木中建立起体胚发生体系，但是存在严重的基因型依赖性，限制了这一生物技术的实际应用。本文中，作者发现植物多肽激素磺肽素（PSK）不仅能够促进杉木的体胚发生效率，更能够帮助那些顽拗型基因型从头建立起体胚发生体系。杉木原胚团（PEM）褐化以及DCF染色实验均表明，在PEMs被转移到体胚诱导培养基上，很快便产生了ROS爆发。转录组和qRT-PCR实验显示，PSK处理能够在体胚诱导早期通过降低PRXs活性，维持ROS内稳态。而由PSK介导的氧化还原内稳态可能有助于WOX2等体胚发生相关基因在体胚诱导早期的表达。进一步的研究表明，PSK仅是部分通过降低过氧化氢水平来促进杉木体胚诱导，并且过氧化氢水平降低对于PSK介导的顽拗性杉木基因型体胚发生的建立是必须的，但并非充分的。此外，通过在拟南芥中异源过表达ClPSK基因能够显著增强拟南芥的体胚发生以及对过氧化氢胁迫的抗性。综上，本文的研究揭示了植物多肽激素PSK作用于杉木体胚发生的功能，拓宽了我们对于林木体胚发生的理解，同时也为杉木和其他针叶树种的高效且不依赖于基因型的体胚发生体系建立提供了一个可行的方法和参考。