兜兰观赏价值高，繁殖难度大，人工过度采挖和生境破坏导致许多野生种濒临灭绝。在野外条件下需与真菌共生才能萌发，且萌发率低。即使在提供充足营养的无菌播种条件下，大部分兜兰成熟种子依然萌发困难，这成为制约兜兰种质资源保护和规模化生产的瓶颈。我们的前期研究结果表明杏黄兜兰种子中存在结构特殊的H型和C型木质素，其积累量与萌发率存在巨大的相关性。本项目通过转录组测序筛选到可能参与调控木质素合成的关键基因-PaCSE。在前期工作的基础上，将通过在拟南芥、苜蓿和兜兰中进行转基因功能验证和PaCSE酶活分析进一步研究PaCSE在兜兰种子木质素合成代谢中的作用，明确其对种子的机械强度、通透性等与萌发相关特性的作用，从而通过调控PaCSE的表达来部分或完全解除萌发的抑制。本项目的实施不仅在兜兰种子萌发和木质素调控机制的基础研究方面会有突破，也对兜兰种苗的繁殖和生产有重要的指导意义。

Paphiopedilum is an important genus of flowering plant family Orchidaceae with high horticultural value. The wild populations are under the threat of extinction because of over-collection and habitat destruction. Paphiopedilum seeds are tiny and contain no endosperm. In the natural habitat, Paphiopedilum seeds are generally unable to germinate on their own. They need to engage in a mycorrhizal relationship with a fungus that helps to feed the emerging seedling. Even feeding enough nutrient supply in asymbiotic germination, mature seeds of most Paphiopedilum species are still difficult to germinate, which severely restricts the germplasm resources protection and commercial production. Our preliminary studies suggested that C lignin and H lignin were synthesized during embryo development, and their deposition was strongly related to the germination inhibition process. However, the mechanism of how this specialized lignin inhibits germination and its biosynthetic machinery remains unclear. We found a potential key gene involved in the lignin synthesis through transcriptome analysis. In this proposal, we are going to investigate the biochemical function of PaCSE and its effect on seed mechanics、permeability and other germination related parameters. The results from this study will provide theoretical guidance for conservation and commercial production of this endangered species.