棉花萜类化合物代谢及调控

Most cotton cultivars accumulate large amount of gossypol and related sesquiterpene aldehydes in epidermal layers of roots and pigment glands of aerial organs, which function as phytoalexins against pathogens and herbivore insects. Till now, progress has been made in elucidation of gossypol biosynthesis pathway and its regulation, but little is known about other terpenoids, especially volatile monoterpenes and sesquiterpenes. Recently we found that, more than gossypol, glanded cotton plants also produce volatile terpenes that are all nearly undetectable in glandless cottons.Phytochemical and transcriptome analysis of glanded and glandless cotton tissues revealed several terpene synthases contributing to volatile monoterpenes and sesquiterpenes production, and critical transcription factors correlated to terpenoid metabolism. In this project, we are going to systematically analyze volatile terpenes in different cotton tissues and cultivars, characterize corresponding terpene synthases, and functional characterize the critical transcriptional regulator in detail. It will not only provide valuable data to elucidate the biochemical and genetic mechanism of the glandless cotton, but also provide new target genes for engineering terpenoid metabolism, especially those with high economic value.

棉花是重要的经济作物。大多数陆地棉和海岛棉（有腺体棉）的地上组织表面分布着色素腺体，其中积累了棉酚等倍半萜醛类化合物，具有抵御病菌侵袭和害虫的功能。目前虽然棉酚代谢途径研究已取得重要进展，但对棉花挥发性萜类成分代谢研究较少。我们发现，有腺体棉合成大量挥发性单萜和倍半萜，而无腺体棉则几乎不含有挥发性萜类成分。以有腺体棉和无腺体棉近等基因系为材料进行挥发性萜类化合物分析，并通过高通量测序技术对两者转录组进行比较分析，初步筛选和鉴定了单萜和倍半萜合酶以及调控萜类化合物代谢的关键转录因子。本项目将对这些萜类合酶以及转录因子进行深入分析，阐明棉花挥发性萜类代谢过程与调控方式及其与棉酚代谢途径的关系，为进一步分析无腺体棉的形成机制提供线索，并为通过代谢工程方法调控棉花萜类化合物生物合成提供基因资源和技术路线。

萜类化合物在植物与环境的互作中具有重要作用，介导了植物与外界的信息交流，也是植物防御体系的重要组成成分。棉花是世界广泛种植的经济作物，是纺织工业中天然纤维的主要来源。但人们对棉花的次生代谢，尤其是萜类化合物代谢了解很少。本项目利用植株表面富含色素腺体、积累大量倍半萜醛类化合物的有腺体棉品种“CCRI12-G”和植株表面无腺体、不积累倍半萜醛类化合物的无腺体棉品种“CCRI12-GL”，通过比较其代谢组和转录组差异，获得以下成果：（1）分离、鉴定了3个负责棉花大部分挥发性萜类化合物合成的萜类合酶（Terpene synthase，TPS）；（2）通过分析两种棉花材料的转录组数据，结合病毒诱导的基因沉默（VIGS）技术，筛选出一批可能调控萜类化合物代谢的转录因子；（3）分析NAC类转录因子GhNAC1和MYB类转录因子MYBA1的调控功能。本项目为深入研究棉花等植物萜类化合物的代谢调控机制奠定了坚实的基础，同时对于认识植物表面色素腺体发育机制提供了重要线索。