Rhizobial peptidase HrrP cleaves host-encoded signaling peptides and mediates symbiotic compatibility
Name
Price-2015-Rhizobial peptidase.pdf
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Author(s)
Price, Paul A.
Tanner, Houston R.
Dillon, Brett A.
Griffitts, Joel S.
Shabab, Mohammed
Walker, Graham C.
Date Issued
September 2015
Journal
Proceedings of the National Academy of Sciences
Publisher
National Academy of Sciences (U.S.)
Citation
Price, Paul A.; Tanner, Houston R.; Dillon, Brett A.; Shabab, Mohammed; Walker, Graham C. and Griffitts, Joel S. “Rhizobial Peptidase HrrP Cleaves Host-Encoded Signaling Peptides and Mediates Symbiotic Compatibility.” Proceedings of the National Academy of Sciences 112, no. 49 (September 2015): 15244–15249 © 2015 National Academy of Sciences
Version
Final published version
Abstract
Legume–rhizobium pairs are often observed that produce symbiotic root nodules but fail to fix nitrogen. Using the Sinorhizobium meliloti and Medicago truncatula symbiotic system, we previously described several naturally occurring accessory plasmids capable of disrupting the late stages of nodule development while enhancing bacterial proliferation within the nodule. We report here that host range restriction peptidase (hrrP), a gene found on one of these plasmids, is capable of conferring both these properties. hrrP encodes an M16A family metallopeptidase whose catalytic activity is required for these symbiotic effects. The ability of hrrP to suppress nitrogen fixation is conditioned upon the genotypes of both the host plant and the hrrP-expressing rhizobial strain, suggesting its involvement in symbiotic communication. Purified HrrP protein is capable of degrading a range of nodule-specific cysteine-rich (NCR) peptides encoded by M. truncatula. NCR peptides are crucial signals used by M. truncatula for inducing and maintaining rhizobial differentiation within nodules, as demonstrated in the accompanying article [Horváth B, et al. (2015) Proc Natl Acad Sci USA, 10.1073/pnas.1500777112]. The expression pattern of hrrP and its effects on rhizobial morphology are consistent with the NCR peptide cleavage model. This work points to a symbiotic dialogue involving a complex ensemble of host-derived signaling peptides and bacterial modifier enzymes capable of adjusting signal strength, sometimes with exploitative outcomes.
MIT Department
Massachusetts Institute of Technology. Department of Biology
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DOI of Published Version
https://doi.org/10.1073/pnas.1417797112
