Institute of Plant Science and Resources, Okayama University, Kurashiki, Japan.
Faculty of Agriculture, Mulawarman University, Samarinda, Indonesia.
J Exp Bot. 2019 Mar 11;70(5):1683-1696. doi: 10.1093/jxb/erz041.
Feeding of sucking insects, such as the rice brown planthopper (Nilaparvata lugens; BPH), causes only limited mechanical damage on plants that is otherwise essential for injury-triggered defense responses against herbivores. In pursuit of complementary BPH elicitors perceived by plants, we examined the potential effects of BPH honeydew secretions on the BPH monocot host, rice (Oryza sativa). We found that BPH honeydew strongly elicits direct and putative indirect defenses in rice, namely accumulation of phytoalexins in the leaves, and release of volatile organic compounds from the leaves that serve to attract natural enemies of herbivores, respectively. We then examined the elicitor active components in the honeydew and found that bacteria in the secretions are responsible for the activation of plant defense. Corroborating the importance of honeydew-associated microbiota for induced plant resistance, BPHs partially devoid of their microbiota via prolonged antibiotics ingestion induced significantly less defense in rice relative to antibiotic-free insects applied to similar groups of plants. Our data suggest that rice plants may additionally perceive herbivores via their honeydew-associated microbes, allowing them to discriminate between incompatible herbivores-that do not produce honeydew-and those that are compatible and therefore dangerous.
取食会引起植物机械损伤，但这种损伤对触发植物防御反应以抵御草食性昆虫是必不可少的。为了寻找植物感知的、与 BPH 相关的补充激发子，我们检测了 BPH 蜜露分泌物对 BPH 单子叶宿主水稻（Oryza sativa）可能产生的影响。我们发现，BPH 蜜露能强烈激发水稻的直接和间接防御反应，即在叶片中积累植保素，以及叶片释放挥发性有机化合物，从而分别吸引草食性昆虫的天敌。然后，我们检测了蜜露中的激发子活性成分，发现分泌物中的细菌是激活植物防御的原因。蜜露相关微生物对诱导植物抗性的重要性得到了印证，与未摄入抗生素的昆虫相比，长时间摄入抗生素的 BPH 体内的微生物部分缺失，从而导致水稻防御反应明显减弱，而这些昆虫被施加于类似的植物组群。我们的数据表明，水稻植株可能通过其与蜜露相关的微生物额外感知到草食性昆虫，使它们能够区分不产生蜜露的不兼容草食性昆虫和那些产生蜜露且因此危险的草食性昆虫。
