The Key Laboratory of Plant Development and Environmental Adaptation Biology, Ministry of Education, School of Life Sciences, Shandong University, Qingdao, China.
Peking University Institute of Advanced Agricultural Sciences, Weifang, China.
J Exp Bot. 2022 Jun 2;73(11):3711-3725. doi: 10.1093/jxb/erac074.
Plant growth promoting rhizobacteria (PGPR) refer to bacteria that colonize the rhizosphere and contribute to plant growth or stress tolerance. To further understand the molecular mechanism by which PGPR exhibit symbiosis with plants, we performed a high-throughput single colony screening from the rhizosphere, and uncovered a bacterium (named promoting lateral root, PLR) that significantly promotes Arabidopsis lateral root formation. By 16S rDNA sequencing, PLR was identified as a novel sub-species of Serratia marcescens. RNA-seq analysis of Arabidopsis integrated with phenotypic verification of auxin signalling mutants demonstrated that the promoting effect of PLR on lateral root formation is dependent on auxin signalling. Furthermore, PLR enhanced tryptophan-dependent indole-3-acetic acid (IAA) synthesis by inducing multiple auxin biosynthesis genes in Arabidopsis. Genome-wide sequencing of PLR integrated with the identification of IAA and its precursors in PLR exudates showed that tryptophan treatment significantly enhanced the ability of PLR to produce IAA and its precursors. Interestingly, PLR induced the expression of multiple nutrient (N, P, K, S) transporter genes in Arabidopsis in an auxin-independent manner. This study provides evidence of how PLR enhances plant growth through fine-tuning auxin biosynthesis and signalling in Arabidopsis, implying a potential application of PLR in crop yield improvement through accelerating root development.
植物促生根际细菌（PGPR）是指定殖于根际并促进植物生长或增强植物抗逆性的细菌。为了进一步了解 PGPR 与植物共生的分子机制，我们对根际进行了高通量单菌落筛选，发现了一种能显著促进拟南芥侧根形成的细菌（命名为促侧根形成菌，PLR）。通过 16S rDNA 测序，PLR 被鉴定为新的粘质沙雷氏菌亚种。对拟南芥进行 RNA-seq 分析并结合对生长素信号突变体的表型验证表明，PLR 对侧根形成的促进作用依赖于生长素信号。此外，PLR 通过诱导拟南芥中多个生长素生物合成基因的表达，增强了色氨酸依赖的吲哚-3-乙酸（IAA）合成。将 PLR 的全基因组测序与 PLR 分泌物中 IAA 及其前体的鉴定相结合表明，色氨酸处理显著增强了 PLR 产生 IAA 及其前体的能力。有趣的是，PLR 以生长素非依赖的方式诱导拟南芥中多个养分（N、P、K、S）转运基因的表达。本研究为 PLR 通过精细调控拟南芥生长素生物合成和信号转导来增强植物生长提供了证据，暗示了 PLR 在通过加速根系发育来提高作物产量方面的潜在应用。
