Kniskern Joel M, Traw M Brian, Bergelson Joy
Department of Ecology and Evolution, University of Chicago, 60637, USA.
Mol Plant Microbe Interact. 2007 Dec;20(12):1512-22. doi: 10.1094/MPMI-20-12-1512.
Terrestrial plants serve as large and diverse habitats for a wide range of pathogenic and nonpathogenic microbes, yet these communities are not well described and little is known about the effects of plant defense on microbial communities in nature. We designed a field experiment to determine how variation in two plant defense signaling pathways affects the size, diversity, and composition of the natural endophytic and epiphytic bacterial communities of Arabidopsis thaliana. To do this, we provide an initial characterization of these bacterial communities in one population in southwestern Michigan, United States, and we compare these two communities among A. thaliana mutants deficient in salicylic acid (SA) and jasmonic acid (JA) signaling defense pathways, controls, and plants with artificially elevated levels of defense. We identified 30 distinct bacterial groups on A. thaliana that differ in colony morphology and 16S rRNA sequence. We show that induction of SA-mediated defenses reduced endophytic bacterial community diversity, whereas plants deficient in JA-mediated defenses experienced greater epiphytic bacterial diversity. Furthermore, there was a positive relationship between total community size and diversity, indicating that relatively susceptible plants should, in general, harbor higher bacterial diversity. This experiment provides novel information about the ecology of bacteria on A. thaliana and demonstrates that variation in two specific plant-signaling defense pathways can influence bacterial diversity on plants.
陆生植物为各种各样的致病和非致病微生物提供了广阔多样的栖息地，但这些群落尚未得到充分描述，人们对植物防御对自然界微生物群落的影响也知之甚少。我们设计了一项田间试验，以确定两种植物防御信号通路的变异如何影响拟南芥自然内生和附生细菌群落的大小、多样性和组成。为此，我们对美国密歇根州西南部一个种群中的这些细菌群落进行了初步表征，并在缺乏水杨酸（SA）和茉莉酸（JA）信号防御通路的拟南芥突变体、对照植株以及防御水平人工提高的植株之间比较了这两个群落。我们在拟南芥上鉴定出30个在菌落形态和16S rRNA序列上不同的独特细菌类群。我们发现，SA介导的防御诱导降低了内生细菌群落的多样性，而缺乏JA介导防御的植株则具有更高的附生细菌多样性。此外，群落总大小与多样性之间存在正相关关系，这表明一般来说，相对易感的植物应该拥有更高的细菌多样性。该实验提供了有关拟南芥上细菌生态学的新信息，并证明两种特定植物信号防御通路的变异会影响植物上的细菌多样性。
