Identification of Bradyrhizobium elkanii USDA61 Type III Effectors Determining Symbiosis with Vigna mungo

Nguyen, Hien P.; Ratu, Safirah T. N.; Yasuda, Michiko; Teaumroong, Neung; Okazaki, Shin

doi:10.3390/genes11050474

Open AccessArticle

Identification of Bradyrhizobium elkanii USDA61 Type III Effectors Determining Symbiosis with Vigna mungo

by

Hien P. Nguyen

^1,†

,

Safirah T. N. Ratu

²,

Michiko Yasuda

³,

Neung Teaumroong

⁴

and

Shin Okazaki

^2,3,*

¹

Institute of Global Innovation Research (IGIR), Tokyo University of Agriculture and Technology (TUAT), Fuchu, Tokyo 183-8538, Japan

²

United Graduate School of Agricultural Science, TUAT, Fuchu, Tokyo 183-8509, Japan

³

Graduate School of Agriculture, TUAT, Fuchu, Tokyo 183-8509, Japan

⁴

School of Biotechnology, Institute of Agricultural Technology, Suranaree University of Technology (SUT), Ratchasima 30000, Thailand

^*

Author to whom correspondence should be addressed.

^†

Present address: Beltsville Agricultural Research Center (BARC), Agricultural Research Service (ARS), the U.S. Department of Agriculture (USDA), Beltsville, MD 20705, USA.

Genes 2020, 11(5), 474; https://doi.org/10.3390/genes11050474

Submission received: 11 March 2020 / Revised: 20 April 2020 / Accepted: 24 April 2020 / Published: 27 April 2020

(This article belongs to the Special Issue Genetic Evolution of Root Nodule Symbioses)

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Abstract

Bradyrhizobium elkanii USDA61 possesses a functional type III secretion system (T3SS) that controls host-specific symbioses with legumes. Here, we demonstrated that B. elkanii T3SS is essential for the nodulation of several southern Asiatic Vigna mungo cultivars. Strikingly, inactivation of either Nod factor synthesis or T3SS in B. elkanii abolished nodulation of the V. mungo plants. Among the effectors, NopL was identified as a key determinant for T3SS-dependent symbiosis. Mutations of other effector genes, such as innB, nopP2, and bel2-5, also impacted symbiotic effectiveness, depending on host genotypes. The nopL deletion mutant formed no nodules on V. mungo, but infection thread formation was still maintained, thereby suggesting its pivotal role in nodule organogenesis. Phylogenetic analyses revealed that NopL was exclusively conserved among Bradyrhizobium and Sinorhizobium (Ensifer) species and showed a different phylogenetic lineage from T3SS. These findings suggest that V. mungo evolved a unique symbiotic signaling cascade that requires both NFs and T3Es (NopL).

Keywords: symbiosis; T3SS; effectors; NopL; Vigna mungo; Bradyrhizobium elkanii

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MDPI and ACS Style

Nguyen, H.P.; Ratu, S.T.N.; Yasuda, M.; Teaumroong, N.; Okazaki, S. Identification of Bradyrhizobium elkanii USDA61 Type III Effectors Determining Symbiosis with Vigna mungo. Genes 2020, 11, 474. https://doi.org/10.3390/genes11050474

AMA Style

Nguyen HP, Ratu STN, Yasuda M, Teaumroong N, Okazaki S. Identification of Bradyrhizobium elkanii USDA61 Type III Effectors Determining Symbiosis with Vigna mungo. Genes. 2020; 11(5):474. https://doi.org/10.3390/genes11050474

Chicago/Turabian Style

Nguyen, Hien P., Safirah T. N. Ratu, Michiko Yasuda, Neung Teaumroong, and Shin Okazaki. 2020. "Identification of Bradyrhizobium elkanii USDA61 Type III Effectors Determining Symbiosis with Vigna mungo" Genes 11, no. 5: 474. https://doi.org/10.3390/genes11050474

APA Style

Nguyen, H. P., Ratu, S. T. N., Yasuda, M., Teaumroong, N., & Okazaki, S. (2020). Identification of Bradyrhizobium elkanii USDA61 Type III Effectors Determining Symbiosis with Vigna mungo. Genes, 11(5), 474. https://doi.org/10.3390/genes11050474

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Identification of Bradyrhizobium elkanii USDA61 Type III Effectors Determining Symbiosis with Vigna mungo

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