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Animal and plant microbial pathogens deploy effector proteins and virulence factors to manipulate host cell innate immunity, often using unconventional secretion routes that are poorly understood. Transfer RNA (tRNA) anticodon modifications occur across taxa, but few biological functions are known. Here, in the devastating blast fungus Magnaporthe oryzae, we find that unconventional protein secretion in living host rice cells depends on tRNA modification and codon usage. Using gene deletions, mass spectrometry and live-cell imaging, we characterized the M. oryzae Uba4-Urm1 sulfur relay system mediating tRNA anticodon wobble uridine 2-thiolation (s2U34), a conserved modification required for efficient decoding of AA-ending cognate codons. In M. oryzae, cytoplasmic effectors like Pwl2 and AVR-Pita are translocated into host cells via an unconventional secretion route; apoplastic effectors like Bas4 are secreted by the conventional ER-Golgi pathway. Loss of U34 thiolation abolished PWL2 and AVR-PITA (but not BAS4) mRNA translation in host cells. Paromomycin treatment, which increases near-cognate tRNA acceptance, restored Pwl2 and AVR-Pita production in U34 thiolation-deficient mutant strains. Synonymous AA- to ¬¬AG-ending codon changes remediated PWL2 mRNA translation in uba4; in UBA4+, expressing recoded PWL2 resulted in Pwl2 super-secretion that destabilized the microbe-host cell interface. Thus, wobble U34 tRNA thiolation and codon usage tune pathogen unconventional protein secretion in host cells.
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This content will become publicly available on March 31, 2026
A phytoalexin dismantles bacterial type III injectisome
Many Gram-negative bacterial pathogens rely on the secretion system to inject effectors into their host cells, thereby suppressing host immunity and subsequently leading to diseases. In a recent Science paper, Miao et al. identified a plant secondary metabolite that dismantles type III injectisome by targeting the conserved HrcC protein within the secretion apparatus.
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- Award ID(s):
- 2207677
- PAR ID:
- 10592788
- Publisher / Repository:
- Nature Publishing group
- Date Published:
- Journal Name:
- Cell Research
- ISSN:
- 1748-7838
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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