Chu Xitong, Su Huanan, Hayashi Satomi, Gresshoff Peter M, Ferguson Brett J
Integrative Legume Research Group, School of Agriculture and Food Sciences, The University of Queensland, St Lucia, Brisbane, Qld, 4072, Australia.
National Navel Orange Engineering Research Center, Gannan Normal University, Ganzhou, China.
New Phytol. 2022 Apr;234(2):479-493. doi: 10.1111/nph.17902. Epub 2022 Jan 8.
The plant hormone gibberellin (GA) is required at different stages of legume nodule development, with its spatiotemporal distribution tightly regulated. Transcriptomic and bioinformatic analyses established that several key GA biosynthesis and catabolism enzyme encoding genes are critical to soybean (Glycine max) nodule formation. We examined the expression of several GA oxidase genes and used a Förster resonance energy transfer-based GA biosensor to determine the bioactive GA content of roots inoculated with DsRed-labelled Bradyrhizobium diazoefficiens. We manipulated the level of GA by genetically disrupting the expression of GA oxidase genes. Moreover, exogenous treatment of soybean roots with GA induced the expression of key nodulation genes and altered infection thread and nodule phenotypes. GmGA20ox1a, GmGA3ox1a, and GmGA2ox1a are upregulated in soybean roots inoculated with compatible B. diazoefficiens. GmGA20ox1a expression is predominately localized to the transient meristem of soybean nodules and coincides with the spatiotemporal distribution of bioactive GA occurring throughout nodule organogenesis. GmGA2ox1a exhibits a nodule vasculature-specific expression pattern, whereas GmGA3ox1a can be detected throughout the nodule and root. Disruptions in the level of GA resulted in aberrant rhizobia infection and reduced nodule numbers. Collectively, our results establish a central role for GAs in root hair infection by symbiotic rhizobia and in nodule organogenesis.
植物激素赤霉素（GA）在豆科植物根瘤发育的不同阶段发挥作用，其时空分布受到严格调控。转录组学和生物信息学分析表明，几个关键的GA生物合成和分解代谢酶编码基因对大豆（Glycine max）根瘤形成至关重要。我们检测了几个GA氧化酶基因的表达，并使用基于Förster共振能量转移的GA生物传感器来测定接种DsRed标记的慢生根瘤菌的根中生物活性GA的含量。我们通过基因干扰GA氧化酶基因的表达来调控GA水平。此外，用GA对大豆根进行外源处理可诱导关键结瘤基因的表达，并改变感染线和根瘤表型。在接种相容的慢生根瘤菌的大豆根中，GmGA20ox1a、GmGA3ox1a和GmGA2ox1a上调。GmGA20ox1a的表达主要定位于大豆根瘤的过渡分生组织，与整个根瘤器官发生过程中生物活性GA的时空分布一致。GmGA2ox1a表现出根瘤维管束特异性表达模式，而GmGA3ox1a在整个根瘤和根中均可检测到。GA水平的破坏导致异常的根瘤菌感染和根瘤数量减少。总之，我们的结果确立了GA在共生根瘤菌感染根毛和根瘤器官发生中的核心作用。
