节律基因表达调控白蜡属种间杂种抗旱优势的机制研究

Heterosis is revealed based on the biological clock (circadian gene), which is a new way of thinking. The circadian gene is a new type of functional genes (transcription factors), which could regulate target gene expression with large-scale from the point of view of the circadian rhythm. Transcriptome studies of Arabidopsis interspecific hybrids have revealed that two-thirds of the upregulated genes are associated with circadian gene regulation. This study selected parents and superior interspecific hybrid F1 (which show drought tolerance, fast growth and strong adaptability) as materials based on the preliminary results. The transcriptome of the materials treated by drought will be analyzed. Then the similarities and differences of circadian gene and stress-tolerant related gene expression, photosynthetic efficiency, soluble sugar, protein content and starch accumulation will be studied. Based of these results, we analyze some important factors (epigenetic modification and signaling molecules MJ of NO and ABA) influencing circadian gene expression and the effect on the drought tolerance. We study relations between endogenous ABA content, stomatal movement , Ca2 + content and circadian gene expression under stress. The study will reveal the mechanism of the heterosis of drought tolerance in interspecific hybrids of Fraxinus. So far ,Function of rhythm gene in the mechanism of the tree heterosis has not been reported. The results of this study will provide forest tree genetic improvement with new ideas and enrich the heterosis theory.

基于生物钟(节律基因)揭示杂种优势一个全新的思考和尝试。节律基因是一类新型的功能基因（转录因子），能从昼夜节律的角度大范围调控靶基因的表达。拟南芥种间杂种转录组研究揭示，三分之二的上调表达基因都与节律基因的调控相关。本研究拟通过对前期工作选出的抗旱、生长快、适应性强白蜡属种间优良杂种F1及其亲本进行干旱胁迫下转录物组分析、在此基础上比较F1与亲本间在节律基因及抗逆相关基因表达、光合效率、可溶性糖、蛋白含量及淀粉积累等方面的异同，分析影响节律基因表达因素（表观修饰和信号分子MJ、NO和ABA）对其表达及对抗旱优势的影响，结合內源ABA与节律基因表达的关系，综合揭示白蜡属种间杂种的抗旱优势。节律基因在树木杂种优势形成机制中的作用研究还未见报道，本研究的结果将为林木遗传改良提供新的思路，开拓并丰富杂种优势理论。

节律基因能从昼夜节律的角度大范围调控靶基因的表达,其对杂种优势的调控仅在拟南芥种间杂种得到揭示,而且节律基因能参与对植物非生物胁迫抗性的形成。本研究通过对前期工作选出的抗旱、生长快、适应性强白蜡属种间优良杂种F1及其亲本进行干旱等胁迫下转录物组、蛋白组分析和甲基化分析，杂交种基因组甲基化水平低于亲本基因组甲基化水平，且亲本幼苗基因组以内侧胞嘧啶的甲基化为主，F1的则以外侧为主。其F1代DNA甲基化水平较低和甲基化模式经历了较大的调整与杂种优势产生密切相关。转录组和蛋白质组分析也证实 Fl与亲本材料对干旱胁迫表现出不同代谢途径差异。在此基础上发现F1相对于亲本保持着较高的光合参数、抗氧化酶的活性、内源激素的含量以及节律基因（LHY、TOC1）和干旱相关基因的表达量，明确了节律基因表达F1和亲本间没有明显的周期性差异，但在表达幅度上F1显著大于亲本，这可能是杂种优势形成的主要原因；进一步分析影响节律基因表达因素（干旱胁迫、MJ、NO和ABA）对其表达及对抗旱优势的影响，结果表明，这些因素均能显著诱导节律基因和抗逆和信号通路相关基因的表达，F1表达幅度大于亲本，这种综合调控结果也是杂种抗旱优势的来源；最后根据本研究获得一系列节律调控相关基因（FmWRKYs,FmCB1与FmTCPs等基因）表达的相关性及其启动子序列元件的联合分析, 提出节律基因与下游抗逆相关基因调控网络工作模型。总之，白蜡属种间杂种抗逆优势的分子机制产生于：相对于亲本较低的甲基化水平，在逆境下杂交种的节律基因表达幅度高于于亲本，促进下游信号通路相关基因的表达，进而调控下游胁迫响应基因在杂交种与亲本间的差异表达，通过生理响应上的差异，形成杂交种抗逆性优势。节律基因在树木杂种优势形成机制中的作用研究还未见报道，本研究的结果将为林木遗传改良提供新的思路，开拓并丰富杂种优势理论。