大小年毛竹叶对昆虫取食差异响应的分子机制

Moso Bamboo (Phyllostachys heterocycla) was well known for its strong fertility, rapid growth and high economic value, furthermore, it plays an important role in national wood security in China. Development of moso bamboo strict to On-Off year rhyme, it always keeps a reasonable ratio for On- and Off-year individuals. But in commercialize forests, On-year ones are dominating, leads to a more serious pests damage situation. What caused this difference of pest out breaking situation between On- and Off-year moso bamboo? It is well documented that differences from bamboo leaves themselves affected pest species on developments, therefore, the entire communities were reordered on their distributions. These evidences are crucial for forest management and pest control, however, the underlying molecular mechanism still remains unknown. Some conducted researches shown that: PhSPL17 expression level was changing according to On-Off year rhyme, and led to downstream insect resistant genes variations which involved in JA pathway. It is highly possible that, PhSPL17 can negatively regulate PhJAZ1 expression level in transcription level. This hypnosis may perfect explain why On-Off year leaves can response to same insect feeding differently, by connecting aging-related and JA pathway. In this project, we will further explore the aging-related and JA-related functions of PhSPL17 and PhJAZ1 in both Arabidopsis and moso bamboo, also the possible connections between PhSPL17 and PhJAZ1, to find out PhSPL17 -PhJAZ1 based molecular mechanism of different responses to insect herbivores between On and Off year moso bamboo leaves.

毛竹是我国重要的林业经济作物，其生长恪守大小年现象。与大小年比例均衡的花年竹林相比，大年竹占绝对比例的生产用林虫害发生更为严重。是何种差异导致大小年毛竹间虫害发生的差异呢？生态学证据表明竹叶在大小年的差异导致食叶害虫种群的变化，进而影响整个节肢动物群落在林间分布的差异，这些发现对竹林的经营管理以及害虫的防控都至关重要，然而其分子机理尚不明确。申请者前期研究结果显示：毛竹PhSPL17表达水平在大小年交替过程中存在规律性变化，并且极有可能在转录水平负调节JA信号通路重要基因PhJAZ1的表达量，引起下游抗虫基因表达量差异，从而表现出大、小年竹叶对昆虫取食的差异响应。本项目拟通过对毛竹PhSPL17及PhJAZ1在植物年龄（大小年）相关JA信号通路中的功能进行研究，探究PhSPL17-PhJAZ1为基础的毛竹抗虫机制，从而揭示大、小年毛竹叶对昆虫取食差异响应的分子机理。

高强度的经营致使竹林中小大年毛竹的比例失衡，降低了毛竹林节肢动物的多样性，从而降低了竹林对虫害（如刚竹毒蛾）的防御能力，然而其机理依然不明晰。在本项目的支持下，团队从分子生态学角度阐述毛竹大、小年叶部节肢动物多样性的差异来源，也在毛竹大小年（年龄）与食叶害虫互作的分子基础方面实现了突破。通过生物信息学分析得知毛竹中有37个SPL家族蛋白且可以细分为4大类，其中PhSPL17为拟南芥AtSPL9的同源基因且为毛竹PhmiR156的靶基因；通过对不同组织和时间尺度上的定量分析得知，PhSPL17在种子、叶部和地下茎中表达量较高，且叶片中的表达量在年龄尺度上随着换叶节律而波动上升，表明PhSPL17在大小年（年龄层面）影响毛竹自身抗虫性的过程中起重要作用。通过构建突变体、转录组测序和昆虫饲喂实验发现，毛竹PhSPL17表达水平在大小年交替过程中存在规律性变化，并在在转录水平负调节JA信号通路重要基因PhJAZ1的表达量（与模式植物拟南芥不同），引起下游抗虫基因表达量差异，从而表现出大、小年竹叶对昆虫取食的差异响应。以上研究成果表明了:毛竹中，年龄信号途径通过PhSPL17-PhJAZ1为核心的基因与蛋白组学层面的变化去塑造生态学层面的林间节肢动物多样性。该发现也是首次证实林木中生理学上的“大小年”在抗虫中的不同作用，为全面揭示刚竹毒蛾以及其他林木害虫的成灾机理提供了崭新的思路。