Ecology and Evolution of Rhizobia by En Tao Wang & Wen Feng Chen & Chang Fu Tian & J. Peter W. Young & Wen Xin Chen

Author:En Tao Wang & Wen Feng Chen & Chang Fu Tian & J. Peter W. Young & Wen Xin Chen
Language: eng
Format: epub
ISBN: 9789813295551
Publisher: Springer Singapore

Sophora and Its Rhizobia

Comparably, the promiscuous legumes S. flavescens and S. alopecuroides can be nodulated by more than five genera of rhizobia (Jiao et al. 2015a; Zhao et al. 2010) (detailed discussion can be found in Chaps. 7 and 8 of this book). Various rhizobia bearing dissimilar nodC gene sequences and originating from different cross-nodulation groups can effectively nodulate S. flavescens (Fig. 5.7) (Jiao et al. 2015a). Mutants of the nodC gene in different representative rhizobial species failed to nodulate either S. flavescens or their usual host plants, demonstrating the indispensability of the nodC gene or the Nod factor in launching root nodule formation (Liu et al. 2018a). Furthermore, abolition of Nod factor-decorative genes did not change nodulation activity, although it did decrease or increase N2-fixing efficiency (Liu et al. 2018a).

Surprisingly, although identical Nod factors were produced by S. fredii CCBAU 45436 and B. diazoefficiens USDA 110 and they had common host range, the latter could not nodulate S. flavescens (Jiao et al. 2015a). Several mutants were selected from a Tn5 library of USDA 110, and they altered the host range from soybean to S. flavescens (Liu et al. 2018a, b). However, these mutated genes were not related directly to the structural genes of Nod factor synthesis but were involved in metabolic pathways, transporters, chemotaxis and mobility (Liu et al. 2018b). These mutants may have lost their immunostimulation of the S. flavescens plant, so that they were allowed to enter the nodule cells and form functional nodules.

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