PDF(Pubmed)
Abstract：
The symbioses between leguminous plants and nitrogen-fixing bacteria known as rhizobia are well known for promoting plant growth and sustainably increasing soil nitrogen. Recent evidence indicates that hopanoids, a family of steroid-like lipids, promote Bradyrhizobium symbioses with tropical legumes. To characterize hopanoids in Bradyrhizobium symbiosis with soybean, we validated a recently published cumate-inducible hopanoid mutant of Bradyrhizobium diazoefficiens USDA110, Pcu-shc::∆shc. GC-MS analysis showed that this strain does not produce hopanoids without cumate induction, and under this condition, is impaired in growth in rich medium and under osmotic, temperature, and pH stress. In planta, Pcu-shc::∆shc is an inefficient soybean symbiont with significantly lower rates of nitrogen fixation and low survival within the host tissue. RNA-seq revealed that hopanoid loss reduces the expression of flagellar motility and chemotaxis-related genes, further confirmed by swim plate assays, and enhances the expression of genes related to nitrogen metabolism and protein secretion. These results suggest that hopanoids provide a significant fitness advantage to B. diazoefficiens in legume hosts and provide a foundation for future mechanistic studies of hopanoid function in protein secretion and motility.
A major problem for global sustainability is feeding our exponentially growing human population while available arable land decreases. Harnessing the power of plant-beneficial microbes is a potential solution, including increasing our reliance on the symbioses of leguminous plants and nitrogen-fixing rhizobia. This study examines the role of hopanoid lipids in the symbiosis between Bradyrhizobium diazoefficiens USDA110, an important commercial inoculant strain, and its economically significant host soybean. Our research extends our knowledge of the functions of bacterial lipids in symbiosis to an agricultural context, which may one day help improve the practical applications of plant-beneficial microbes in agriculture.
A major problem for global sustainability is feeding our exponentially growing human population while available arable land decreases. Harnessing the power of plant-beneficial microbes is a potential solution, including increasing our reliance on the symbioses of leguminous plants and nitrogen-fixing rhizobia. This study examines the role of hopanoid lipids in the symbiosis between Bradyrhizobium diazoefficiens USDA110, an important commercial inoculant strain, and its economically significant host soybean. Our research extends our knowledge of the functions of bacterial lipids in symbiosis to an agricultural context, which may one day help improve the practical applications of plant-beneficial microbes in agriculture.
摘要：
豆科植物和固氮细菌之间的共生关系被称为根瘤菌，以促进植物生长和持续增加土壤氮而闻名。最近的证据表明类大麻，一类类固醇类脂,促进缓生根瘤菌与热带豆类共生。为了表征缓生根瘤菌与大豆共生的类hopanoid，我们验证了最近发表的一种累积诱导的大豆根瘤菌突变体USDA110，Pcu-shc::Δshc。GC-MS分析表明，该菌株在没有累积诱导的情况下不产生类大麻素，在这种情况下,在丰富的培养基和渗透条件下生长受损，温度,和pH胁迫。在植物中,Pcu-shc::Δshc是一种低效的大豆共生体，固氮率明显较低，宿主组织内存活率低。RNA-seq显示，类胡萝卜素的丢失会降低鞭毛运动和趋化性相关基因的表达，通过游泳板测定进一步证实，并增强与氮代谢和蛋白质分泌相关的基因的表达。这些结果表明，类大麻为豆科植物宿主中的B.diazoefficens提供了显着的适应性优势，并为未来类大麻在蛋白质分泌和运动中的功能机理研究奠定了基础。
全球可持续发展的一个主要问题是养活我们指数增长的人口，而可用耕地减少。利用植物有益微生物的力量是一个潜在的解决方案，包括增加我们对豆科植物和固氮根瘤菌共生的依赖。这项研究检查了类hopanoid脂质在重氮根瘤菌USDA110之间的共生关系中的作用，该菌株是一种重要的商业接种菌株，及其具有经济意义的寄主大豆。我们的研究将我们对共生中细菌脂质功能的了解扩展到农业环境，这可能有一天有助于改善植物有益微生物在农业中的实际应用。
全球可持续发展的一个主要问题是养活我们指数增长的人口，而可用耕地减少。利用植物有益微生物的力量是一个潜在的解决方案，包括增加我们对豆科植物和固氮根瘤菌共生的依赖。这项研究检查了类hopanoid脂质在重氮根瘤菌USDA110之间的共生关系中的作用，该菌株是一种重要的商业接种菌株，及其具有经济意义的寄主大豆。我们的研究将我们对共生中细菌脂质功能的了解扩展到农业环境，这可能有一天有助于改善植物有益微生物在农业中的实际应用。
