Establishment of symbiosis between plants and arbuscular mycorrhizal (AM) fungi depends on fungal chitooligosaccharides (COs) and lipo‐chitooligosaccharides (LCOs). The latter are also produced by nitrogen‐fixing rhizobia to induce nodules on leguminous roots. However, host enzymes regulating structure and levels of these signals remain largely unknown. Here, we analyzed the expression of a β‐ We found that expression of In conclusion, we identified an enzyme, which inactivates COs and promotes the AM symbiosis. We hypothesize that GlcNAc produced by MtHEXO2 may function as a secondary symbiotic signal.
Ecological interactions range from purely specialized to extremely generalized in nature. Recent research has showed very high levels of specialization in the cyanolichens involving Here, we characterized interactions between After splitting the interaction matrix into modules of preferentially interacting partners, we evaluated how module membership might have evolved along the mycobionts’ phylogeny. We also teased apart the contributions of geographical overlap vs phylogeny in driving interaction establishment between Module affiliation rarely evolves through the splitting of large ancestral modules. Instead, new modules appear to emerge independently, which is often associated with a fungal speciation event. We also found strong phylogenetic signal in these interactions, which suggests that partner switching is constrained by conserved traits. Therefore, it seems that a high rate of fungal diversification following a switch to a new cyanobiont can lead to the formation of large modules, with cyanobionts associating with multiple closely retated Finally, when restricting our analyses to
- PAR ID:
- 10461140
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Journal of Ecology
- Volume:
- 107
- Issue:
- 4
- ISSN:
- 0022-0477
- Page Range / eLocation ID:
- p. 1645-1661
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Summary N ‐acetylhexosaminidase gene ofMedicago truncatula (MtHEXO2 ) and biochemically characterized the enzyme. Mutant analysis was performed to study the role ofMtHEXO2 during symbiosis.MtHEXO2 is associated with AM symbiosis and nodulation.MtHEXO2 expression in the rhizodermis was upregulated in response to applied chitotetraose, chitoheptaose, and LCOs.M. truncatula mutants deficient in symbiotic signaling did not show induction ofMtHEXO2 . Subcellular localization analysis indicated that MtHEXO2 is an extracellular protein. Biochemical analysis showed that recombinant MtHEXO2 does not cleave LCOs but can degrade COs intoN ‐acetylglucosamine (GlcNAc).Hexo2 mutants exhibited reduced colonization by AM fungi; however, nodulation was not affected inhexo2 mutants. -
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