植物激素与克隆整合对入侵植物抗病的生态效应及调控

Invasive plants were attacked by few pathogens in its invaded habitats, but the intrinsic reasons were little known. Our previous studies on a notorious invasive clonal plant Wedelia trilobata showed that its populations in invaded habitats were attacked by few pathogens, the endogenous gibberellins content in W. trilobata was very high and gibberellins promoted its clonal growth significantly. And various plant hormones signal could response to the pathogen attack. The ability of resistance to pathogen of W. trilobata was also greater than its native congener W. chinensis. We hypothesize that the invasive plant could regulate clonal integration through plant hormones, and conversely, clonal integration could transport plant hormones to connected ramets and affect the resistance ability to pathogen of the whole plant. To test the hypothesis, we will combine the methods of molecular biology, biochemistry, plant physiology and ecology to study the effects of plant hormone in the clonal integration and the mechanism of plant hormone response to the pathogen attack in invasive plants. This project combines plant hormone and clonal integration these two new insights to investigate the intrinsic reasons of invasive plant attacking by few pathogens. And the results will better explain the invasion mechanism and control invasive clonal plants.

成功的外来植物在入侵地较少受害于病原天敌，其中原因仍知之甚少。基于我们前期关于恶性入侵克隆植物南美蟛蜞菊(Wedelia trilobata)的研究发现：其野外种群很少受到病原菌侵染、其内源赤霉素含量很高并能促进克隆生长、其体内多种激素信号功能响应病原侵染、其抗病性高于本地近缘种蟛蜞菊(W. chinensis)，我们推测入侵克隆植物可能通过激素调控克隆整合，并利用克隆整合转运激素到相连分株，从而影响分株的整体抗病性。为验证我们的假设，本项目拟综合利用分子生物学、生物化学、植物生理学及比较生态学等方法，以入侵克隆植物南美蟛蜞菊为例，探讨激素对入侵克隆植物克隆分株生长、克隆整合作用的影响及其在克隆分株间响应病原的作用机理。项目创新性地结合植物激素与克隆整合作用这一新视角探讨入侵植物较少受害于病原天敌的内在原因，研究结果有助于更好地阐释外来克隆植物的入侵机制及未来对入侵克隆植物的防治。

外来植物入侵严重影响全球生态系统的稳定，我们前期研究表明，外来入侵植物南美蟛蜞菊(Wedelia trilobata)在野外很少受到病虫害的侵染，本项目通过探究植物激素及克隆整合作用在入侵植物抗病性中的重要作用，以解释入侵植物的强抗病性。研究发现入侵植物南美蟛蜞菊内源赤霉素的含量显著高于本地植物蟛蜞菊，且赤霉素显著促进南美蟛蜞菊根及茎的伸长。而赤霉素合成抑制剂多效唑则显著抑制南美蟛蜞菊根及茎的伸长。赤霉素含量与茎的伸长有显著相关性。而本地同属植物蟛蜞菊(W. chinensis)根及茎的生长与赤霉素含量没有显著相关性。入侵植物南美蟛蜞菊的抗病虫能力显著高于本地植物蟛蜞菊。南美蟛蜞菊的叶片水提液也显著抑制病原真菌及植食性昆虫幼虫的生长。丛枝菌根真菌显著促进南美蟛蜞菊在低磷营养中的生长及竞争力，丛枝菌根真菌也能显著提高南美蟛蜞菊的抗病性，同时克隆整合作用也能提高相连茎段的抗病原真菌能力。入侵植物空心莲子草(Alternanthera philoxeroides)的抗病原真菌能力显著高于本地同属植物莲子草(A. sessilis)。克隆整合作用显著提高相连茎段的抗病性，通过基因表达发现，接种病原真菌后，空心莲子草和莲子草的水杨酸，茉莉酸和乙烯的6个相关基因（PAL, PR3, LOX, JAR1, PR6, 和 EIN3）的表达量有显著的差异；在外源施加植物激素水杨酸、茉莉酸、乙烯后，相关基因的表达量在两个物种间也有显著差异。本研究结果表明植物激素、丛枝菌根真菌显著促进入侵植物的生长，也能促进入侵植物的抗病能力，且入侵植物的化感作用及克隆整合作用也能显著提高入侵植物的抗病虫能力。研究结果为解释外来植物的成功入侵提供新思路，可为下一步利用微生物防控入侵克隆杂草的实践提供理论基础。