共生匹配性与共生不匹配性，植物的免疫系统对根瘤菌的作用

陈文峰

2018年10月21日

共生固氮体系的建立，需要根瘤菌与豆科植物双方的分子互作与交流；而对于豆科植物来说，是否能容纳根瘤菌与自己共生，还决定于豆科植物的免疫系统。2018年9月我们发表在Microbiological Research杂志上的论文——高效固氮慢生根瘤菌USDA 110突变体与苦参和大豆的共生特征[Symbiotic characteristics of Bradyrhizobium diazoefficiens USDA 110 mutants associated with shrubby sophora (Sophora flavescens) and soybean (Glycine max)]，通过构建根瘤菌的突变体库，从中筛选到了本来只能刺激苦参形成小凸起的假根瘤，瘤内并没有根瘤菌，而突变体却可以进行根瘤内，并形成有一定固氮活性的根瘤。这显然是突变体的一些基因被突变后，不再产生特殊的蛋白，因此，不再刺激植物的免疫系统，根瘤菌最终得以进入到根瘤内部，并与植物建立共生关系。

论文摘要：

Site-specific insertion plasmid pVO155 was used to knockout the genes involved in the alternation of host range of strain Bradyrhizobium diazoefficiens USDA 110 from its original determinate-nodule-forming host soybean (Glycine max), to promiscuous and indeterminate-nodule-forming shrubby legume sophora (Sophora flavescens). Symbiotic phenotypes of these mutants inoculated to these two legumes, were compared to those infected by wild-type strain USDA 110. Six genes of the total fourteen Tn5 transposon mutated genes were broken using the pVO155 plasmid. Both Tn5 and pVO155-inserted mutants could nodulate S. flavescenswith different morphologies of low-efficient indeterminate nodules. One to several rod or irregular bacteroids, containing different contents of poly-β-hydroxybutyrate or polyphosphate were found within the symbiosomes in nodulated cells of S. flavescens infected by the pVO155-inserted mutants. Moreover, none of bacteroids were observed in the pseudonodules of S. flavescens, infected by wild-type strain USDA 110. These mutants had the nodulation ability with soybean but the symbiotic efficiency reduced to diverse extents. These findings enlighten the complicated interactions between rhizobia and legumes, i. e., mutation of genes involved in metabolic pathways, transporters, chemotaxis and mobility could alter the rhizobial entry and development of the bacteroid inside the nodules of a new host legume.

上图：野生型的USDA110(WT)及各种突变体(BDT-2, ..., -28)接种于苦参后的共生表型。

上图：野生型的USDA110及各种pvo155插入突变体(BDT-2pvo, ..., ...BDT-28pvo)接种于苦参后的共生表型。

上图：被Tn5或pvo155插入突变的基因的位置。

下表：被Tn5插入的基因的特征：

论文还对根瘤菌的运动性、对镁离子的利用情况进行了研究，见论文的附件部分。

全文见这里：

https://www.sciencedirect.com/science/article/pii/S0944501317311400 

或点击下面下载全文：

刘元辉突变体论文RM最终版-包括附件.pdf

以下内容来自于PubMed数据库：

Microbiol Res. 2018 Sep;214:19-27. doi: 10.1016/j.micres.2018.05.012. Epub 2018 May 21.

Symbiotic characteristics of Bradyrhizobium diazoefficiens USDA 110 mutants associated with shrubby sophora (Sophora flavescens) and soybean (Glycine max).

Liu YH1, Wang ET2, Jiao YS1, Tian CF1, Wang L1, Wang ZJ1, Guan JJ1, Singh RP3, Chen WX1, Chen WF4.

Author information

• 1 State Key Laboratory of Agrobiotechnology, Beijing 100193, China; College of Biological Sciences and Rhizobium Research Center, China Agricultural University, Beijing 100193, China.

• 2 Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, México D. F. 11340, México.

• 3 Microbial Genomics Laboratory, National Bureau of Agriculturally Important Microorganisms, Maunath Bhanjan, Uttar Pradesh 275101, India.

• 4 State Key Laboratory of Agrobiotechnology, Beijing 100193, China; College of Biological Sciences and Rhizobium Research Center, China Agricultural University, Beijing 100193, China. Electronic address: chenwf@cau.edu.cn.

Abstract

Site-specific insertion plasmid pVO155 was used to knockout the genes involved in the alternation of host range of strain Bradyrhizobiumdiazoefficiens USDA 110 from its original determinate-nodule-forming host soybean (Glycine max), to promiscuous and indeterminate-nodule-forming shrubby legume sophora (Sophora flavescens). Symbiotic phenotypes of these mutants inoculated to these two legumes, were compared to those infected by wild-type strain USDA 110. Six genes of the total fourteen Tn5 transposon mutated genes were broken using the pVO155 plasmid. Both Tn5 and pVO155-inserted mutants could nodulate S. flavescens with different morphologies of low-efficient indeterminate nodules. One to several rod or irregular bacteroids, containing different contents of poly-β-hydroxybutyrate or polyphosphate were found within the symbiosomes in nodulated cells of S. flavescens infected by the pVO155-inserted mutants. Moreover, none of bacteroids were observed in the pseudonodules of S. flavescens, infected by wild-type strain USDA 110. These mutants had the nodulation ability with soybean but the symbiotic efficiency reduced to diverse extents. These findings enlighten the complicated interactions between rhizobia and legumes, i. e., mutation of genes involved in metabolic pathways, transporters, chemotaxis and mobility could alter the rhizobial entry and development of the bacteroid inside the nodules of a new host legume.

KEYWORDS:

Bradyrhizobium diazoefficiens USDA 110; Nodulation; Sophora flavescens; Soybean (Glycine max); Symbiotic characterization; Tn5 mutation

• PMID: 30031478

•  

• DOI: 10.1016/j.micres.2018.05.012