木质素代谢调控芍药花茎机械强度的机理研究

Mechanical strength is a mechanical parameter measuring inflorescence stem straight degree of cut flower. The insufficient mechanical strength of inflorescence stem in herbaceous peony (Paeonia lactiflora Pall.) can cause inflorescence stem bending and flower drooping, which seriously affect the quality of cut flower. Previous studies have ascertained that lignin is the main chemical composition affecting the mechanical strength of P. lactiflora inflorescence stem, but the mechanism of where lignin deposition, what type of lignin accumulation and what gene regulation affecting the mechanical strength of P. lactiflora inflorescence stem is unclear yet. In this project, scanning electron microscopy, transmission electron microscopy, histochemical staining, high performance liquid chromatography and 13C nuclear magnetic resonance methods will be used to clarify the relationship between anatomy characteristics and physiological properties related to lignin metabolism and the mechanical strength of P. lactiflora inflorescence stem. On the other hand, the comparative analysis of transcriptome based on RNA-seq technology, gene expression pattern detection, gene expressing active site observation and gene subcellular localization observation will be used to definite the key genes regulating lignin metabolism of inflorescence stem, and further sequence variation or methylation level will be investigated to reveal the regulation mechanism of key gene expression. Eventually, these results would systematically elucidate the mechanism of lignin metabolism regulation on the mechanical strength of P. lactiflora inflorescence stem from the structural, physiological and molecular levels, which would provide theoretical basis for improving the quality of inflorescence stem in P. lactiflora cut flower.

机械强度是衡量切花茎秆挺直程度的力学参数。芍药花茎机械强度不足易致花茎弯曲、花朵下垂，严重影响切花品质。前期研究表明，木质素是影响芍药花茎机械强度的主要化学成分，但对于木质素在芍药花茎什么部位沉积、以什么类型积累、受什么基因调控等不同层面影响花茎机械强度的机理尚不清楚。本项目拟运用扫描电镜、透射电镜、组织化学染色、高效液相色谱、核磁共振13C谱等技术来弄清与木质素代谢相关的解剖结构特征、生理特性与芍药花茎机械强度的关系；另一方面，采用基于RNA-seq技术的转录组学比较分析、基因表达模式检测、表达活性部位观察与亚细胞定位观察来明确调控花茎木质素代谢的关键基因，并进一步从序列差异、DNA甲基化修饰入手来揭示基因表达的调控机制。最终，从结构水平、生理水平、分子水平等多个层面详尽地阐明木质素代谢调控芍药花茎机械强度机理，为芍药切花在花茎品质方面的改良提供理论依据。

芍药花茎机械强度不足容易导致花茎弯曲、花朵下垂，严重影响切花品质。前期研究表明，木质素是影响芍药花茎机械强度的主要化学成分。项目组以芍药花茎机械强度差异显著的2个品种为材料，运用扫描电镜、透射电镜、组织化学染色等技术对花茎解剖结构差异进行观察，发现木质部次生细胞壁的加厚及其木质化程度是影响芍药花茎机械强度的主要解剖结构特征；运用高效液相色谱、核磁共振13C谱等技术对花茎与木质素代谢相关的生理特性差异进行观测，发现S-木质素是影响芍药花茎机械强度的主要化学组分，它又受到木质素生物合成酶的调控。同时，对2个品种的花茎混样进行了第三代转录组测序，共得到113,974个转录本，其中105,382 Unigenes被注释。在此基础之上，运用比较转录组学技术系统地探究了芍药花茎机械强度在转录水平上的差异，共筛选到10个参与木质素合成的DEGs表达模式与花茎木质素含量趋势相一致，进一步通过系统的分子生物学研究明确了PlHCT1基因定位于细胞质和细胞核中，在花茎机械强度调控中的重要作用，并揭示了它在2个品种中的表达差异是由序列变异造成的调控机制。这一结果从结构水平、生理水平、分子水平等多个层面阐明了木质素代谢调控芍药花茎机械强度机理，为芍药切花在花茎品质方面的改良提供理论依据。