Jiangsu Provincial Key Lab of Solid Organic Waste Utilization, Jiangsu Collaborative Innovation Center of Solid Organic Wastes, Nanjing Agricultural University, Nanjing, Jiangsu, China.
J Basic Microbiol. 2021 Jun;61(6):569-575. doi: 10.1002/jobm.202100098. Epub 2021 Apr 29.
The phytohormone indole-3-acetic acid (IAA) has been demonstrated to contribute to the plant growth-promoting effect of rhizobacteria, but the IAA biosynthesis pathway in rhizobacteria remains unclear. The ysnE gene, encoding a putative tryptophan acetyltransferase, has been demonstrated to be involved in and strongly contribute to IAA production in Bacillus, but the mechanism is unknown. In this study, to investigate how ysnE participates in IAA biosynthesis in the plant growth-promoting rhizobacterium Bacillus amyloliquefaciens SQR9, differences in the produced IAA biosynthesis intermediates between wild-type SQR9 and ΔysnE were analyzed and compared, and the effects of different intermediate compounds on the production of IAA and the accumulation of other intermediates were also investigated. The results showed that the mutant ΔysnE produced more indole-3-lactic acid (ILA) and tryptamine (TAM) than the SQR9 wild-type strain (nearly 1.6- and 2.1-fold), while the production of tryptophol (TOL) was significantly decreased by 46%. When indole-3-pyruvic acid (IPA) served as the substrate, the concentration of ILA in the ΔysnE fermentation broth was much higher than that of the wild type, while IAA and TOL were significantly lower, and ΔysnE was lower than SQR9 in IAA and TOL with the addition of TAM. The TOL content in the ΔysnE fermentation broth was much lower than that in the wild-type SQR9 with the addition of ILA. We suggest that ysnE may be involved in the IPA and TAM pathways and play roles in indole acetaldehyde (IAAld) synthesis from IPA and TAM and in the conversion of ILA to TOL.
植物激素吲哚-3-乙酸（IAA）已被证明有助于根际细菌的植物生长促进作用，但根际细菌中的 IAA 生物合成途径尚不清楚。已证明编码色氨酸乙酰转移酶的 ysnE 基因参与并强烈促进芽孢杆菌中 IAA 的产生，但机制尚不清楚。在这项研究中，为了研究 ysnE 如何参与植物促生根际细菌解淀粉芽孢杆菌 SQR9 中的 IAA 生物合成，分析并比较了野生型 SQR9 和ΔysnE 之间产生的 IAA 生物合成中间产物的差异，还研究了不同中间化合物对 IAA 产生和其他中间产物积累的影响。结果表明，突变体ΔysnE 比 SQR9 野生型菌株产生更多的吲哚-3-乳酸（ILA）和色胺（TAM）（近 1.6-和 2.1 倍），而色醇（TOL）的产量则显著降低了 46%。当吲哚-3-丙酮酸（IPA）作为底物时，ΔysnE 发酵液中 ILA 的浓度远高于野生型，而 IAA 和 TOL 的浓度则显著降低，并且添加 TAM 时，ΔysnE 的 IAA 和 TOL 含量均低于 SQR9。添加 ILA 时，ΔysnE 发酵液中的 TOL 含量远低于野生型 SQR9。我们认为，ysnE 可能参与 IPA 和 TAM 途径，并在 IPA 和 TAM 合成吲哚乙醛（IAAld）以及 ILA 转化为 TOL 中发挥作用。
