Rehman Hafiz Mamoon, Cheung Wai-Lun, Wong Kwong-Sen, Xie Min, Luk Ching-Yee, Wong Fuk-Ling, Li Man-Wah, Tsai Sau-Na, To Wing-Ting, Chan Lok-Yi, Lam Hon-Ming
Center for Soybean Research of the State Key Laboratory of Agrobiotechnology and School of Life Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong.
Front Microbiol. 2019 Nov 12;10:2569. doi: 10.3389/fmicb.2019.02569. eCollection 2019.
is a dominant rhizobium on alkaline-saline land that can induce nitrogen-fixing symbiotic root nodules in soybean. Two strains, CCBAU25509 and CCBAU45436, were used in this study to facilitate in-depth analyses of this species and its interactions with soybean. We have previously completed the full assembly of the genomes and detailed transcriptomic analyses for these two strains, CCBAU25509 and CCBAU45436, that exhibit differential compatibility toward some soybean hosts. In this work, we performed high-throughput Orbitrap analyses of the whole proteomes and secretomes of CCBAU25509 and CCBAU45436 at different growth stages. Our proteomic data cover coding sequences in the chromosome, chromid, symbiotic plasmid, and other accessory plasmids. In general, we found higher levels of protein expression by genes in the chromosomal genome, whereas proteins encoded by the symbiotic plasmid were differentially accumulated in bacteroids. We identified secreted proteins from the extracellular medium, including seven and eight Nodulation Outer Proteins (Nops) encoded by the symbiotic plasmid of CCBAU25509 and CCBAU45436, respectively. Differential host restriction of CCBAU25509 and CCBAU45436 is regulated by the allelic type of the soybean Rj2(Rfg1) protein. Using sequencing data from this work and available in public databases, our analysis confirmed that the soybean Rj2(Rfg1) protein has three major allelic types (Rj2/rfg1, rj2/Rfg1, rj2/rfg1) that determine the host restriction of some and strains. A mutant defective in the type 3 protein secretion system (T3SS) in CCBAU25509 allowed this strain to nodulate otherwise-incompatible soybeans carrying the rj2/Rfg1 allelic type, probably by disrupting Nops secretion. The allelic forms of NopP and NopI in might be associated with the restriction imposed by Rfg1. By swapping the NopP between CCBAU25509 and CCBAU45436, we found that only the strains carrying NopP from CCBAU45436 could nodulate soybeans carrying the rj2/Rfg1 allelic type. However, no direct interaction between either forms of NopP and Rfg1 could be observed.
是盐碱地上的优势根瘤菌，能够在大豆中诱导形成固氮共生根瘤。本研究使用了两株菌株CCBAU25509和CCBAU45436，以促进对该物种及其与大豆相互作用的深入分析。我们之前已经完成了这两株菌株CCBAU25509和CCBAU45436的基因组全组装及详细的转录组分析，这两株菌株对某些大豆宿主表现出不同的兼容性。在这项工作中，我们对CCBAU25509和CCBAU45436在不同生长阶段的全蛋白质组和分泌蛋白质组进行了高通量的Orbitrap分析。我们的蛋白质组数据涵盖了染色体、染色体外基因座、共生质粒和其他辅助质粒中的编码序列。总体而言，我们发现染色体基因组中的基因具有较高水平的蛋白质表达，而共生质粒编码的蛋白质在类菌体中差异积累。我们从细胞外培养基中鉴定出分泌蛋白，包括分别由CCBAU25509和CCBAU45436的共生质粒编码的7种和8种结瘤外蛋白（Nops）。CCBAU25509和CCBAU45436对宿主的不同限制受大豆Rj2（Rfg1）蛋白等位基因类型调控。利用本研究的测序数据和公共数据库中的可用数据，我们的分析证实大豆Rj2（Rfg1）蛋白有三种主要等位基因类型（Rj2/rfg1、rj2/Rfg1、rj2/rfg1），它们决定了某些菌株对宿主的限制。CCBAU25509中III型蛋白质分泌系统（T3SS）缺陷的突变体使该菌株能够与携带rj2/Rfg1等位基因类型的原本不兼容的大豆结瘤，可能是通过破坏Nops分泌实现的。CCBAU45436中NopP和NopI的等位基因形式可能与Rfg1施加的限制有关。通过在CCBAU25509和CCBAU45436之间交换NopP，我们发现只有携带来自CCBAU45436的NopP的菌株能够与携带rj2/Rfg1等位基因类型的大豆结瘤。然而，未观察到任何一种形式的NopP与Rfg1之间的直接相互作用。
