Extended Hopanoid Loss Reduces Bacterial Motility and Surface Attachment and Leads to Heterogeneity in Root Nodule Growth Kinetics in a Bradyrhizobium-Aeschynomene Symbiosis.
Extended Hopanoid Loss Reduces Bacterial Motility and Surface Attachment and Leads to Heterogeneity in Root Nodule Growth Kinetics in a Bradyrhizobium-Aeschynomene Symbiosis.
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长时间的 Hopanoid 损失会降低细菌的活力和表面附着，并导致慢生根瘤菌-Aeschynomene 共生中根瘤生长动力学的异质性。
DOI：
10.1094/mpmi-04-19-0111-r
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Newman,DianneK
中科院分区：
文献类型：
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作者：
Belin,BrittanyJ;Tookmanian,EliseM;deAnda,Jaime;Wong,GerardCL;Newman,DianneK
Hopanoids是类固醇样细菌脂质，其增强膜刚性并促进细菌在不同应力下的生长。Hopanoid生物合成基因在固氮植物共生体中是保守的，我们以前发现，在热带豆科植物Aeschynomene afraspera中，Bradyrhizobium diazoefficiens中的扩展（C35）类Hopanoid是高效共生固氮所必需的。在这里，我们表明，固氮缺陷所赋予的延长hopanoid损失可以完全解释根瘤大小的减少，而不是每类细菌固氮水平。使用单结节跟踪方法定量A. afrasperanoprotein的发展，我们提供了一个定量模型的根瘤发育在这个主机，揭示了野生型结节的基线生长参数和一个令人惊讶的异质性扩展hopanoid突变体发育表型。这些表型包括根瘤启动延迟和存在生长速率缓慢和最终体积低的根瘤亚群，这分别与体外运动性和表面附着力降低和植物中类菌体密度降低相关。这项工作提供了一个定量的参考点，了解表型多样性的无效共生体在A。afrasperaand确定了受扩展的hopanoid损失影响的特定发育阶段，用于未来的机制工作。
Hopanoids are steroid-like bacterial lipids that enhance membrane rigidity and promote bacterial growth under diverse stresses. Hopanoid biosynthesis genes are conserved in nitrogen-fixing plant symbionts, and we previously found that the extended (C35) class of hopanoids inBradyrhizobium diazoefficiensare required for efficient symbiotic nitrogen fixation in the tropical legume hostAeschynomene afraspera. Here, we demonstrate that the nitrogen-fixation defect conferred by extended hopanoid loss can be fully explained by a reduction in root nodule sizes rather than per-bacteroid nitrogen-fixation levels. Using a single-nodule tracking approach to quantifyA. afrasperanodule development, we provide a quantitative model of root nodule development in this host, uncovering both the baseline growth parameters for wild-type nodules and a surprising heterogeneity of extended hopanoid mutant developmental phenotypes. These phenotypes include a delay in root nodule initiation and the presence of a subpopulation of nodules with slow growth rates and low final volumes, which are correlated with reduced motility and surface attachment in vitro and lower bacteroid densities in planta, respectively. This work provides a quantitative reference point for understanding the phenotypic diversity of ineffective symbionts inA. afrasperaand identifies specific developmental stages affected by extended hopanoid loss for future mechanistic work.