无芒隐子草闭花授粉机制研究

In China, the 90% of total grasslands are degraded under a very degree. The native grasses, such as Cleistogenes songorica, which adapt the local environment very well, are important foundation for reclamation of degraded grasslands and improvement of environment. Our previous research results showed that the cleistogamous (CL) and chasmogamous (CH) are existed contemporarily in C. songorica. The seed yield in CL are contribute of 82% of total seed yield in C. songorica. Up to now, the mechanism of CL is still unclear. Further research will concentrate on morphology and cytology of the spikelet and floral organs in both CL and CH. For the first time, transcription Unigenes will be released in C. songorica based on intergrating genomic DNA sequencing, RNA transcriptome and Small RNA sequecing of floret. Meanwhile, more than 10 novel cDNA genes and Small RNAs related with CL should be functionly identified and reveal the correlationship between CL and drought stress among these Unigenes. The results will illuminate the reproductive allocation between CL and CH in C. songorica, also the cytology and molecular mechanism of CL. These work will provide the technical support for the seed production and extension of C. songorica cultivar, will also increase the understanding of CL in angiosperm.

我国90% 的草地已不同程度退化，充分利用能适应当地环境的的乡土草资源（如旱生性无芒隐子草），是改良退化草地、改善生态环境的有效之途。我们的前期研究发现，无芒隐子草同时存在闭花授粉（CL）和开花授粉（CH），CL小穗的种子产量约占总产量的82%，但造成这种差异的机制尚未阐明。本项目拟进一步研究CL和CH小穗、花器官的形态学、细胞学基础；首次以CL家族植物无芒隐子草整合基因组DNA测序、RNA转录组和Small RNA测序研究其CL的分子动态，验证10个以上CL相关cDNA和Small RNA的生物学功能以及CL与抗旱基因的关联性；从而揭示无芒隐子草CL和CH繁殖分配，CL的细胞和分子机理。为无芒隐子草新品种的种子生产和推广利用提供技术支撑，也为被子植物CL机制奠定理论基础。

研究发现无芒隐子草具有闭花授粉(CL)和开花授粉(CH)小花及由此产生的种子差异是其适应荒漠逆境的重要策略。无芒隐子草茎杆不同部位产生的种子产量和质量存在显著差异(P< 0.05)；不同部位小花在花器构造、形态和不同发育阶段均存在差异；显微观察表明，CL和CH浆片、花粉粒外观及表面纹饰均存在差异。通过Illumina、PacBio和Hi-C测序及组装得到异源四倍体无芒隐子草高质量的染色体水平基因组，大小为543Mb，共54383个蛋白编码基因。整合全基因组DNA、mRNA和miRNA对CL和CH花器官进行分析，共鉴定出5类miRNA及71个可能调控花发育的基因，并在全基因组水平鉴定出63个ABCDE模型基因和87个bZIP转录因子，其中两个FD基因(属于bZIP家族)可能同时调控无芒隐子草的抗旱和闭花特性。miR172的靶基因AP2可抑制开花整合调控基因AP1的表达，从而调控植株的开花；而AP2主要通过抑制FT-FD途径影响AP1的表达。无芒隐子草miR172和其靶基因AP2分别超表达水稻后，引起了转基因植株花器官发育变异。研究结果丰富了被子植物闭花授粉的形态和分子基础，为无芒隐子草新品种的种子生产和推广利用提供技术支撑。