The Medicago truncatula nodule-specific cysteine-rich peptides, NCR343 and NCR-new35 are required for the maintenance of rhizobia in nitrogen-fixing nodules.

Horvath, B.; Gungor, B.; Toth, M.; Domonkos, A.; Ayaydin, F.; Saifi, F.; Chen, Y.; Biro, J. B.; Bourge, M.; Szabo, Z.; Toth, Z.; Chen, R.; Kalo, P.

doi:10.1101/2023.01.23.523609

bioRxiv · 10.1101/2023.01.23.523609

The Medicago truncatula nodule-specific cysteine-rich peptides, NCR343 and NCR-new35 are required for the maintenance of rhizobia in nitrogen-fixing nodules.

Horvath, B.·Gungor, B.·Toth, M.·Domonkos, A.·Ayaydin, F.·Saifi, F.·Chen, Y.·Biro, J. B.·Bourge, M.·Szabo, Z.·Toth, Z.·Chen, R.·Kalo, P.

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Abstract

In the nodules of Inverted Repeat-Lacking Clade legumes, including M. truncatula, nitrogen-fixing rhizobia undergo terminal differentiation resulting in elongated and endoreduplicated bacteroids specialised for nitrogen fixation. This irreversible transition of rhizobia is mediated by host produced nodule-specific cysteine-rich (NCR) peptides, of which about 700 are encoded in the M. truncatula genome. Some of these NCR peptides, NCR169, NCR211 and NCR247, are essential for nitrogen-fixing symbiosis. The analysis of bacteroid and symbiotic host cell differentiation revealed that the symbiotic phenotype of M. truncatula mutants, Mtsym19, Mtsym20 and NF-FN9363, were defective likewise in the formerly studied ncr mutants, Mtdnf4-1 and Mtdnf7-2. The incomplete differentiation of bacteroids triggered premature senescence of rhizobia in the nitrogen fixation zones of mutant nodules. Mtsym19 and Mtsym20 mutants are defective in the same peptide NCR-new35 and the lack of NCR343 is responsible for the ineffective symbiosis of NF-FN9363. The activity of NCR-new35 is significantly lower and limited to the transition zone of the nodule compared with other crucial NCRs. The fluorescent protein-tagged version of NCR343 and NCR-new35 localize to the symbiotic compartment. Our discovery added two additional members to the group of NCR genes essential for nitrogen-fixing symbiosis in M. truncatula.

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Horvath, B., Gungor, B., Toth, M., Domonkos, A., Ayaydin, F., Saifi, F., Chen, Y., Biro, J. B., Bourge, M., Szabo, Z., Toth, Z., Chen, R., Kalo, P.. 2023-01-23. The Medicago truncatula nodule-specific cysteine-rich peptides, NCR343 and NCR-new35 are required for the maintenance of rhizobia in nitrogen-fixing nodules.. https://doi.org/10.1101/2023.01.23.523609

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