biostudies-literatureChen MMinisterio de Ciencia, Tecnología e InnovaciónSwiss National Science FoundationGobierno de Aragón1458-1474https://www.ebi.ac.uk/biostudies/studies/S-EPMC12489286biostudies-literatureUnknown248(3)In symbiotic plant-microbe interactions, the host invests considerable amounts of resources in the microbial partner. If the microbe does not reciprocate with a comparable symbiotic benefit, it is regarded as a cheater. The host responds to cheaters with negative feedback mechanisms (sanctions) to prevent fitness deficits resulting from being exploited. We study sanctioning in the symbiosis between Medicago truncatula and the nitrogen-fixing rhizobium Sinorhizobium meliloti. We manipulated the exchange of resources between the partners in three ways: by using mutant rhizobia defective in nitrogenase; replacing nitrogen in the atmosphere with argon gas; and supplying rich nitrogen fertilizer to the host. We follow the consequences of simulated cheating by examining the metabolome and proteoThe New phytologistInhibition of rhizobial cheaters by the host Medicago truncatula involves repression of symbiotic functions and induction of defense.PMC12489286E35_23RMCIN/AEI/10.13039/501100011033310030200367310030_200367Raisin AYruela IAllard PMStumpe MReinhardt DChen MJudkins NDefossez EBecana MfalseInhibition of rhizobial cheaters by the host Medicago truncatula involves repression of symbiotic functions and induction of defense.In symbiotic plant-microbe interactions, the host invests considerable amounts of resources in the microbial partner. If the microbe does not reciprocate with a comparable symbiotic benefit, it is regarded as a cheater. The host responds to cheaters with negative feedback mechanisms (sanctions) to prevent fitness deficits resulting from being exploited. We study sanctioning in the symbiosis between Medicago truncatula and the nitrogen-fixing rhizobium Sinorhizobium meliloti. We manipulated the exchange of resources between the partners in three ways: by using mutant rhizobia defective in nitrogenase; replacing nitrogen in the atmosphere with argon gas; and supplying rich nitrogen fertilizer to the host. We follow the consequences of simulated cheating by examining the metabolome and proteo2025-01-01T00:00:00Z2025 Nov2026-06-04T01:54:05.717Z2026-05-04T03:14:08.254ZS-EPMC124892864091015310.1111/nph.70494