茜草科花粉发育、内壁加厚突出的功能及其演化

Great advance has been made in pollen morphology of Rubiaceae in the past three decades, a few peculiar palynological features have been identified, e.g., protruding oncus, which has important value in phylogenetic analysis in the family. So far,developmental ultrastructure of pollen wall was studied on limited rubiaceae taxa. The evolutionary pattern of the pollen wall, how the protruding onci behave during pollen germation are still unknown. Molecular study on pollen wall development is becoming a new hot area of palynological research. Dozens of genes that controls the pollen wall development have been reported in model plants e.g.,Arabidopsis, a few genes such like MS1, FLA3 controls the intine formation are also isolated and characterized. .This proposal aims to: (1) study the developmental ultrastructure of pollen wall of the representative taxa from the phylogenetic tree of Rubiaceae, analysis the evolutionary pattern of the pollen wall structure and development in Rubiaceae, (2)study the chemical composition of the protruding oncus, and its behavior and biological funtion during pollen gemination,(3)clone the gene(s) that controls the protruding intine, the expression pattern of the gene(s) during the wall development and how the gene(s) evolve in the family， so as to build a scientific foundation for constructing the evo-devo pattern of pollen wall in the family.

茜草科孢粉形态在过去三十年内得到了较为全面的研究，表明茜草科花粉发育及其花粉壁超微结构性状的演化值得进一步的探讨。茜草科花粉内壁在萌发孔沟区域形成的加厚突起结构在茜草科族级水平具有重要的系统学价值。花粉发育过程中涉及近万种特异基因的表达,迄今在拟南芥、烟草等模式植物中发现了几十种花粉发育特异基因，其中包括几种调节花粉内壁发育的特异基因。因此本课题拟在被子植物系统发育框架下，结合多学科手段方法对茜草科的花粉发育及花粉壁结构开展进一步的研究，旨在探讨（1）花粉壁发育在茜草科中的演化式样（2）内壁加厚突出结构的化学本质、生物学功能（3）内壁加厚突出结构发生过程中的关键基因，从细胞水平和分子水平诠释花粉内壁加厚突出结构的起源、发生发育和生物学功能，从而从形态、个体发育到功能基因的分子发育相统一的角度构建茜草科花粉壁的进化发育（Evo-devo）式样，为研究茜草科植物孢粉学的分子进化积累科学资料。

茜草科孢粉形态学研究表明，该科的花粉发育及其花粉壁超微结构性状的演化值得进一步的探讨。本课题在茜草科系统发育框架下，结合细胞生物学、发育生物学和分子生物学等多学科方法对茜草科的花粉发育及花粉壁结构开展了进一步的研究，（1）观察了代表茜草科分支类群的6种植物的花粉发育的超微结构变化，包括茜草亚科的鸡屎藤、丰花草、五星花，龙船花亚科的龙船花和栀子花，以及金鸡纳亚科的希茉莉，其中栀子花的花粉代表四合花粉类型的发育过程，其余5种为单粒花粉。（2）对茜草科花粉内壁加厚突出的功能进行了探讨。（3）构建了希茉莉的花药转录组，以及小孢子母细胞阶段、四分体阶段、单核小孢子和双核小孢子时期等4个不同发育阶段的表达谱。基于生物信息学的方法筛选到了243个差异表达基因和108个阶段特异表达基因是与绒毡层发育、孢粉素合成和花粉壁发育相关的候选基因，为进一步研究希茉莉花药和花粉发育的功能基因打下了基础。本项目的研究结果为被子植物花粉演化的分子机制积累了科学资料。