中间型无花果夏果与秋果单性结实差异的赤霉素代谢与响应途径的转录组解析

San Pedro type (Ficus carica var. Intermedia Shinn) is one of the four types of figs (F. carica L.), the varieties produce two crops a year, the breba and the main crop grow on the same tree sequentially. Breba of San Pedro type cultivars are parthenocarpic, while the main crop requires pollination to complete fruit development. The main crop production of San Pedro type figs has not achieved in China as lacking of species specific wasp to carry out the pollination. The present proposal is submitted to elucidate the mechanism underlying the parthenocarpic difference of breba and main crop of San Pedro type figs. Following the parthenocarpic character changes after braba received gibberellin synthesis inhibition treatments and main crop received exogenous gibberellin applications, high throughout and in-depth transcriptomic analysis will be carried out by RNA-sequencing based technology. On the identical genetic background of the breba and main crop materials, multiple comparisons will be carried out on fruit development process and transcriptomic changes of the inflorescent tissues after gibberellin interference treatments which will be applied around the physiological mature stage of female flowers. Differentially expressed genes from transcriptomic comparisons will be analyzed with special focus on gibberellin synthesis and metabolism, gibberellin signaling and transduction pathways, and cross-talks among signal pathways and cellular processes. Expression model cluster grouping, gene ontology (GO) function and metabolism pathway gathering, protein-protein interaction network analysis will be carried out for in-depth analysis, in addition with the full sequence and promoter clone and validation of key genes of differential expression, the dominate/central regulatory pathways and the important control points will be highlighted to judge the role of gibberellin regulation pathways in fig parthenocarpy realization. The expected results of this proposal will primarily reveal the mechanism underlying the parthenocarpic character of San Prdro type figs, and lay ground for applied research on cultivation measure establishment to successfully induce parthenocarpic main crop of San Pedro type figs.

中间型无花果是无花果的四个品种类型之一，同株生长夏、秋两种果实类型。夏果具有单性结实能力，而秋果需授粉才能完成发育。我国没有无花果专性授粉黄蜂，限制了中间型无花果栽培品种秋果的生产。本申请针对中间型无花果夏、秋果的单性结实生理差异，通过夏果赤霉素合成抑制与秋果外源赤霉素处理诱导夏、秋果单性结实能力变化，开展以RNA深度测序技术为依托的转录组学研究，多重对比相同遗传背景下夏、秋果发育过程和雌花生理成熟期赤霉素干预前后花序组织转录组学差异，以赤霉素合成、代谢与响应途径和相关细胞信号途径交互串话变化为核心切入点，展开转录组表达模式聚类、GO功能与代谢途径显著性富集和蛋白质互作网络分析，结合重要差异基因功能与启动子转录模式验证，探查无花果单性结实的主控途径和重要网络节点，判读赤霉素调控途径的地位和作用，初步解析中间型无花果单性结实的调控机理，为秋果单性结实控制与应用研究奠定基础。

中间型无花果的夏果具有单性结实能力，而秋果为非单性结实，需要授粉才能完成生长发育，但我国没有无花果专性授粉小黄蜂，造成秋果脱落无法正常成熟，严重制约其在我国的生产与推广。为解析中间型无花果夏秋果单性结实差异的机理，本项目依托转录组学研究，辅以生理生化指标的测定，对比分析了第一快速生长阶段不同时期的中间型无花果夏、秋果中植物激素合成、分解与信号转导途径的表达，并与夏、秋果均可单性结实的普通型无花果相比较，结合不同生长调节剂处理，实现对无花果单性结实机理的初步解析。结果发现，与夏果相比，中间型秋果中GA和IAA合成以及GA和ABA响应途径受抑制、ABA合成和ETH响应增强，具体表现为IAA氨基酸水解酶基因和GA20ox显著下调，GA2ox、CKX、NCED和ACS显著上调；在信号通路中，AUX/IAA、DELLA、PP2C 和ERF显著上调。普通型无花果秋果中ABA和ETH的合成及响应基因NCED、ACS、PP2C 和ERF也均上调。初步推测IAA、GA和CTK合成与响应途径转录水平上的抑制是导致中间型无花果秋果脱落的主要原因。植物生长调节剂处理发现采用25mg/l的GA3或CPPU处理盛花期果实（直径为20-25mm）均可诱导中间型秋果的单性结实。对处理后2、4和10天的花托与雌花分析显示处理后植物激素水平和基因表达模式表现出时空的差异。随着果实发育，花托与雌花中由激素处理引起的差异表达基因逐渐趋于一致。GA3和CPPU处理均引起NCED表达下调，ABA合成受抑制；促进活性GA的产生，不同的是前者是通过抑制GA2ox表达，即GA失活受阻，后者是通过提高GA20ox和GA3ox的表达，促进合成来实现的。本项目探索了无花果在早期果实发育期植物激素代谢与信号转导途径基因的表达模式，解析了植物激素的作用机制，并进一步解析和判读了赤霉素和细胞分裂素在无花果单性结实的多层面调控中所处地位和所起作用，为植物生长调节剂在单性结实无花果的诱导提供理论依据。已发表第一标注SCI论文3篇，已投稿第一标注SCI论文1篇，正在准备第一标注SCI论文2篇，一发表第一标注国内核心期刊论文1篇，获国家植物新品种权1项。