College of Sciences, Henan Agricultural University, Key Laboratory of Enzyme Engineering of Agricultural Microbiology, Ministry of Agriculture, Zhengzhou, 450002, China.
Mol Plant Microbe Interact. 2019 Jun;32(6):750-759. doi: 10.1094/MPMI-11-18-0317-R. Epub 2019 Apr 29.
Plant growth-promoting rhizobacteria (PGPR) and fungi-bacterial biofilms are both important biofertilizer inoculants for sustainable agriculture. However, the strongest chemoattractant for bacteria to colonize the rhizosphere and mycelia is not clear. Coincidentally, almost all the PGPRs possess 1-aminocyclopropane-1-carboxylate (ACC) deaminase (AcdS) and can utilize ACC as the sole nitrogen source. Here, we found that ACC was a novel, metabolic dependent and methyl-accepting chemoreceptor-involved chemoattractant for UW4. The chemotactic response of UW4 to ACC is significantly greater than that to the amino acids and organic acids identified in the plant root and fungal hyphal exudates. The colonization counts of the UW4 or deletion mutants in the wheat rhizosphere and on mycelia were reduced one magnitude compared with those of UW4. The colonization counts of UW4 on antisense ACC oxidase mycelia with a high ACC production significantly increased compared with , followed by the UW4 complementary strain and the ethylene chemoreceptor gene-deletion mutant. The colonization counts of the UW4 strains on mycelia with a low ACC production decreased significantly compared with wild type. These results suggested that ACC and not ethylene should be the strongest chemoattractant for the PGPR that contain AcdS.
植物促生根际细菌（PGPR）和真菌-细菌生物膜都是可持续农业的重要生物肥料接种剂。然而，对于细菌在根际和菌丝体上定殖的最强化学引诱剂尚不清楚。巧合的是，几乎所有的 PGPR 都具有 1-氨基环丙烷-1-羧酸（ACC）脱氨酶（AcdS），并可以将 ACC 用作唯一的氮源。在这里，我们发现 ACC 是 UW4 的一种新型、代谢依赖性和甲基接受型化学感受受体参与的化学引诱剂。UW4 对 ACC 的趋化反应明显大于对植物根系和真菌菌丝分泌物中鉴定出的氨基酸和有机酸的趋化反应。与 UW4 相比，UW4 或 缺失突变体在小麦根际和菌丝上的定殖计数减少了一个数量级。与 UW4 相比，UW4 对 ACC 氧化酶菌丝体（高 ACC 产量）的定殖计数显著增加，其次是 UW4 互补菌株和乙烯化学感受受体基因缺失突变体。与野生型相比，UW4 菌株在 ACC 产量低的菌丝体上的定殖计数显著减少。这些结果表明，对于含有 AcdS 的 PGPR，ACC 而不是乙烯应该是最强的化学引诱剂。
