粳稻亚种内杂种劣势相关基因克隆及其互作分析

Hybrid vigor is a universal phenomenon existed in nature, yet hybrid weakness phenomenon was also uncovered occasionally in the practice with applying hybrid plant breeding. As a form of post-zygotic reproductive barriers, hybrid weakness in interspecific, intersubspecific as well as intrasubspecific of plant hybrids, perform a vital role in reproductive isolation and potentially hinder the full utilization of heterosis. Nevertheless, only a few genes conferring hybrid weakness has been cloned in Arabdopsis in dicots, while our understanding of the molecular mechanisms underlying of hybrid weakness in rice and monocots is still limited to date. Fortunately, we discovered three japonica rice cultivars (Aranghyangchalbyeo, Shinseonchalbyeo and Sanghaehyangheolua) which caused hybrid weakness in the hybrids derived from crosses by any two of them as parents. Previously, we identified the phenotypic performances, genetic bases and genetic inheritance of hybrid weakness genes Hwc1, Hwc2 and Hwc3(t) harboring in those japonica rice cultivars. Owing to biological and evolutionary significance, this study will be aimed to further cloning and complementation test of hybrid weakness genes Hwc1, Hwc2 and Hwc3(t), analyze gene expression and interaction ,molecular regulatory network and reveal the molecular mechanisms underlying of hybrid weakness in japonica intrasubspecific hybrids, by map-based cloning, fusion protein expression, in situ hybridization, Microarray, Whole genome resequencing etc. Therefore, the findings of this study would bring new insights into our understanding of speciation and hybrid weakness in rice and monocots and may benefit japonica hybrid rice breeding.

杂种优势是自然界的普遍现象，但在植物杂交育种实践中也时常发现杂种劣势现象。植物种间、亚种间或品种间的杂种劣势作为一种合子后生殖隔离形式，在生殖隔离中扮演重要角色，它阻碍了人们对杂种优势的充分利用。然而迄今只有少数拟南芥等双子叶植物的杂种劣势基因被克隆，我们对水稻及单子叶植物杂种劣势分子机制的认识还十分有限。申请人有幸发现三个粳稻品种两两杂交均表现劣势现象，初步探明该劣势的表型、类别、相关候选基因分布及遗传模式等。鉴于杂种劣势在生物学和进化上的重要意义，本研究旨在利用图位克隆、遗传转化、原位杂交、基因芯片、全基因组重测序等技术，克隆和验证粳稻劣势相关基因Hwc1、Hwc2和Hwc3(t)，分析其时空表达模式及基因互作分子调控网络，解析粳稻亚种内杂种劣势的分子机制。该分子机制的阐明将为完善杂交育种理论、突破粳稻杂种优势瓶颈提供新思路，并可能在水稻及单子叶植物杂种劣势及物种分化理论上取得新突破。

杂种劣势是自然种群之间重要的合子后生殖屏障。相对于杂种优势，杂种劣势现象无论在产量、生物量以及其他经济性状都表现极差。杂种劣势在杂交水稻中会造成植株矮化生长，根形成异常，会阻碍营养吸收并且降低产量。目前在种间、种内乃至品种间、品种内均有杂种劣势相关报道。在两个遗传背景差异较大的亲本杂交过程中，杂种劣势现象会造成潜在的阻碍作用。目前，已有大量关于水稻杂种优势遗传基础的研究报道，反观目前关于杂种劣势现象的分子机制研究却很少，缺乏对杂种劣势的分子基础解析便难以在杂交育种中充分利用杂种优势。因此，解析诸如水稻等重要作物中的杂种劣势现象的分子机制则十分必要。.本研究报道了三个粳稻品种Aranghyangchalbyeo (CH7)、Sanghaehyangheolua(CH8) 、Shinseonchalbyeo (CH9)，两两杂交 F1 代均表现出劣势现象，首次探讨了粳稻亚种内杂交杂种劣势的遗传和生理过程，克隆了水稻杂种劣势基因Hwc1、Hwc3，验证了Hwc2基因位点。本研究创新性地发现了由逆转录转座子驱动的粳稻杂种劣势现象，并通过水稻遗传转化对其进行了验证，揭示了Hwc1和Hwc3互作导致杂种劣势形成的分子机制。全基因组重测序结果表明，所选粳稻植株中存在大量的多态性，当两个基因组杂交时，基因组水平多态性可能不能很好地互补，这可能最终导致在F1后代中表现出发育缺陷。基因表达谱芯片研究的结果表明，亲本和两两杂交 F1杂交种之间基因表达谱变化显著，粳亚种内的某种生殖屏障可能是新基因表达的结果。.本研究在水稻乃至单子叶植物杂种劣势形成机制方面取得了新的突破，为我们更好的探索杂种优势理论提供了新的视角，同时为完善杂交育种理论及突破粳稻杂种优势瓶颈提供了新思路。