College of Life Sciences, Henan Agricultural University, Key Laboratory of Enzyme Engineering of Agricultural Microbiology, Ministry of Agriculture and Rural Affairs, Zhengzhou, China.
College of Sciences, Henan Agricultural University, Zhengzhou, China.
Mol Plant Pathol. 2024 Nov;25(11):e70026. doi: 10.1111/mpp.70026.
Plant root border cells (RBCs) prevent the colonization of plant growth-promoting rhizobacteria (PGPR) at the root tip, rendering the PGPR unable to effectively control pathogens infecting the root tip. In this study, we engineered four strains of Pseudomonas sp. UW4, a typical PGPR strain, each carrying an enhanced green fluorescent protein (EGFP)-expressing plasmid. The UW4E strain harboured only the plasmid, whereas the UW4E-flg22 strain expressed a secreted EGFP-Flg22 fusion protein, the UW4E-Flg(flg22) strain expressed a non-secreted Flg22, and the UW4E-flg22-D strain expressed a secreted Flg22-DNase fusion protein. UW4E-flg22 and UW4E-flg22-D, which secreted Flg22, induced an immune response in wheat RBCs and colonized wheat root tips, whereas the other strains, which did not secrete Flg22, failed to elicit this response and did not colonize wheat root tips. The immune response revealed that wheat RBCs synthesized mucilage, extracellular DNA, and reactive oxygen species. Furthermore, the Flg22-secreting strains showed a 33.8%-93.8% higher colonization of wheat root tips and reduced the root rot incidence caused by Rhizoctonia solani and Fusarium pseudograminearum by 24.6%-35.7% compared to the non-Flg22-secreting strains in pot trials. There was a negative correlation between the incidence of wheat root rot and colonization of wheat root tips by these strains. In contrast, wheat root length and dry weight were positively correlated with the colonization of wheat root tips by these strains. These results demonstrate that engineered secretion of Flg22 by PGPR is an effective strategy for controlling root rot and improving plant growth.
植物根边缘细胞（RBC）阻止植物促生根际细菌（PGPR）在根尖处定殖，使 PGPR 无法有效控制感染根尖的病原体。在本研究中，我们构建了四株假单胞菌 UW4 的工程菌株，UW4 是一种典型的 PGPR 菌株，每个菌株都携带一个增强型绿色荧光蛋白（EGFP）表达质粒。UW4E 菌株仅携带质粒，而 UW4E-flg22 菌株表达分泌型 EGFP-Flg22 融合蛋白，UW4E-Flg(flg22)菌株表达非分泌型 Flg22，UW4E-flg22-D 菌株表达分泌型 Flg22-DNase 融合蛋白。分泌 Flg22 的 UW4E-flg22 和 UW4E-flg22-D 诱导小麦 RBC 产生免疫反应并定殖小麦根尖，而其他不分泌 Flg22 的菌株则无法引起这种反应，也无法定殖小麦根尖。免疫反应表明，小麦 RBC 合成了黏液、细胞外 DNA 和活性氧。此外，与不分泌 Flg22 的菌株相比，在盆栽试验中，分泌 Flg22 的菌株对小麦根尖的定殖率提高了 33.8%-93.8%，对 Rhizoctonia solani 和 Fusarium pseudograminearum 引起的根腐病的发病率降低了 24.6%-35.7%。小麦根腐病的发病率与这些菌株对小麦根尖的定殖呈负相关。相比之下，小麦根长和干重与这些菌株对小麦根尖的定殖呈正相关。这些结果表明，工程菌通过分泌 Flg22 来控制根腐病和促进植物生长是一种有效的策略。
