Department of Plant Pathology and Microbiology, National Taiwan University, Taipei, 10617, Taiwan.
Department of Entomology and Plant Pathology, Auburn University, Auburn, AL, 36849, USA.
Plant J. 2021 Jun;106(6):1588-1604. doi: 10.1111/tpj.15257. Epub 2021 May 18.
The rhizosphere is a multitrophic environment, and for soilborne pathogens such as Fusarium oxysporum, microbial competition in the rhizosphere is inevitable before reaching and infecting roots. This study established a tritrophic interaction among the plant growth-promoting rhizobacterium Burkholderia ambifaria, F. oxysporum and Glycine max (soybean) to study the effects of F. oxysporum genes on shaping the soybean microbiota. Although B. ambifaria inhibited mycelial growth and increased bacterial propagation in the presence of F. oxysporum, F. oxysporum still managed to infect soybean in the presence of B. ambifaria. RNA-Seq identified a putative F. oxysporum secretory β-lactamase-coding gene, FOXG_18438 (abbreviated as Fo18438), that is upregulated during soybean infection in the presence of B. ambifaria. The ∆Fo18438 mutants displayed reduced mycelial growth towards B. ambifaria, and the complementation of full Fo18438 and the Fo18438 β-lactamase domain restored mycelial growth. Using the F. oxysporum wild type, ∆Fo18438 mutants and complemented strains with full Fo18438, Fo18438 β-lactamase domain or Fo18438 RTA1-like domain for soil inoculation, 16S rRNA amplicon sequencing revealed that the abundance of a Burkholderia operational taxonomic unit (OTU) was increased in the rhizosphere microbiota infested by the strains with Fo18438 β-lactamase domain. Non-metric multidimensional scaling and PICRUSt2 functional analysis revealed differential abundance for the bacterial β-lactam-related functions when contrasting the genotypes of F. oxysporum. These results indicated that the Fo18438 β-lactamase domain provides F. oxysporum with the advantage of growing into the soybean rhizosphere, where β-lactam antibiosis is involved in microbial competition. Accordingly, this study highlights the capability of an F. oxysporum gene for altering the soybean rhizosphere and taproot microbiota.
根际是一个多营养环境，对于土壤病原菌如尖孢镰刀菌，在到达并感染根部之前，根际中的微生物竞争是不可避免的。本研究在植物促生菌伯克霍尔德氏菌和尖孢镰刀菌与大豆（Glycine max）之间建立了一个三营养层相互作用，以研究尖孢镰刀菌基因对塑造大豆微生物组的影响。尽管伯克霍尔德氏菌在存在尖孢镰刀菌的情况下抑制菌丝生长并增加细菌繁殖，但尖孢镰刀菌仍然设法在存在伯克霍尔德氏菌的情况下感染大豆。RNA-Seq 鉴定出一个假定的尖孢镰刀菌分泌β-内酰胺酶编码基因，FOXG_18438（简称 Fo18438），该基因在存在伯克霍尔德氏菌时在大豆感染过程中上调。∆Fo18438 突变体对伯克霍尔德氏菌的菌丝生长显示出减少，而完全 Fo18438 和 Fo18438 β-内酰胺酶结构域的互补恢复了菌丝生长。使用尖孢镰刀菌野生型、∆Fo18438 突变体和用完整 Fo18438、Fo18438 β-内酰胺酶结构域或 Fo18438 RTA1 样结构域互补的菌株进行土壤接种，16S rRNA 扩增子测序显示，在 Fo18438 β-内酰胺酶结构域存在的菌株感染的根际微生物群中，伯克霍尔德氏菌操作分类单元（OTU）的丰度增加。非度量多维尺度和 PICRUSt2 功能分析表明，当对比尖孢镰刀菌基因型时，细菌β-内酰胺相关功能的丰度存在差异。这些结果表明，Fo18438 β-内酰胺酶结构域为尖孢镰刀菌提供了进入大豆根际的优势，其中β-内酰胺抗生性参与了微生物竞争。因此，本研究强调了尖孢镰刀菌基因改变大豆根际和主根微生物组的能力。
