Microbial enhancement of plant nutrient acquisition | SpringerLink

摘要

养分有效性是作物产量和质量的决定因素。虽然施肥是改善植物营养的主要途径，但其效果可能有限，肥料的生产和应用经常给环境带来问题。大量的土壤微生物能够增强植物营养的获取，从而提供环境友好的解决方案，以满足植物营养的要求。在此，我们总结了有益微生物如何促进植物获取大量营养素和微量营养素。我们还回顾了最近关于营养依赖性植物-微生物相互作用的研究，这些研究突出了植物在建立或阻止植物-微生物关联方面的主动性。通过剖析根微生物组内微生物之间的复杂信号相互作用，将有可能更好地了解特定生物和非生物胁迫下微生物增强的植物营养。

Fig.1 Microbe-enhanced plant acquisition of macronutrients and micronutrients. Beneficial microbes enhance plant nutrient acquisition via multiple mechanisms, including but not limited to [a] N2 fixation by rhizobia in nodules or by non-nodulating diazotrophs; [b] Nutrient uptake and delivery through mycorrhizal mycelia that reaches additional soil beyond the root; [c] Mobilization of soil-fixed nutrients through ion exchange or chelation by bacterial or fungal secretions, such as organic acids and siderophores; [d] Microbe-induced transcriptional regulation of plant genes involved in nutrient uptake, such as Arabidopsis Fe deficiency responses that are induced by bacteria volatile organic compounds (VOCs). Microbes may also enhance plant S nutrition via certain S-containing VOCs, such as dimethyl disulfite, which can be assimilated by the aerial portion of plants.

图1  微生物促进植物获取大量和微量营养元素。有益微生物通过多种机制促进植物养分的获取，包括但不限于[a] 结瘤或非结瘤固氮菌对氮的固定；[b] 通过菌根菌丝体吸收和输送养分，使其到达根部以外的额外土壤；[c] 通过细菌或真菌分泌物（如有机酸和铁载体）的离子交换或螯合来动员土壤固定养分；[d] 微生物诱导的参与营养吸收的植物基因的转录调节，例如由细菌挥发性有机化合物（VOCs）诱导的拟南芥缺铁反应。微生物还可以通过某些含S的VOCs（如二甲基二硫醚）增强植物的S营养，这些VOCs可以被植物的空中部分吸收。

Fig.2 Nutrition-dependent plant-microbe association highlights plant’s initiative in determining the relationships. a Low N availability increases root production of flavonoids, which induce rhizobial production of nodulation factors that in turn provoke nodule formation for N2 fixation. By contrast, high N availability transcriptionally induces CLE35, which suppresses rhizobia infection and consequently nodulation (Moreau et al. 2021). b Under P sufficient conditions, Arabidopsis plants respond to the GB03-released volatile compound diacetyl with decreases in the microbe-induced ROS burst, thereby providing a permissive environment for the bacterial association; whereas under P deficient conditions, the plants respond to diacetyl with strong activation of salicylic acid (SA)- and jasmonic acid (JA)-mediated defense, thereby deterring the bacterial association (Morcillo et al. 2020). By contrast, Arabidopsis deploy a different strategy for determining the relation with C. tofieldiae, an endophytic fungus that can transfer phosphate to its host. The plants allow the symbiosis with C. tofieldiae only under P deficient conditions; whereas under P sufficient conditions, the plants deploy Trp-derived antifungal metabolites to deter the endophytic colonization of C. tofieldiae (Hiruma et al. 2016)

图2 营养依赖的植物-微生物联合强调了植物在确定关系方面的主动性。a 低氮有效性增加了根的黄酮类化合物产量，这会诱导根瘤菌产生结瘤因子，进而促使根瘤形成以固定N2。相比之下，高氮利用率转录诱导CLE35，从而抑制根瘤菌感染，从而抑制结瘤（Moreau等人，2021）。b 在P充足的条件下，拟南芥植株响应GB03释放的挥发性化合物二乙酰，减少微生物诱导的ROS爆发，从而为细菌结合提供了一个允许的环境；而在缺磷条件下，植物对二乙酰的反应是强烈激活水杨酸（SA）和茉莉酸（JA）介导的防御，从而阻止细菌的结合（Morcillo等人，2020）。相比之下，拟南芥采用了一种不同的策略来确定与C.tofieldiae的关系，C.tofieldia是一种内生真菌，可以将磷酸盐转移到宿主。只有在缺磷条件下，植物才允许与C.tofieldiae共生；而在P充足的条件下，植物部署Trp衍生的抗真菌代谢物，以阻止C.tofieldiae的内生定植（Hiruma等人，2016）