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Eukaryotic filamentous plant pathogens with biotrophic growth stages like the devastating hemibiotrophic rice blast fungus Magnaporthe oryzae grow for extended periods in living host plant cells without eliciting defense responses. M. oryzae elaborates invasive hyphae (IH) that grow in and between living rice cells while separated from host cytoplasm by plant-derived membrane interfaces. However, although critical to the plant infection process, the molecular mechanisms and metabolic strategies underpinning this intracellular growth phase are poorly understood. Eukaryotic cell growth depends on activated target-of-rapamycin (TOR) kinase signaling, which inhibits autophagy. Here, using live-cell imaging coupled with plate growth tests and RNAseq, proteomic, quantitative phosphoproteomics and metabolic approaches, we show how cycles of autophagy in IH modulate TOR reactivation via α-ketoglutarate to sustain biotrophic growth and maintain biotrophic interfacial membrane integrity in host rice cells. Deleting the M. oryzae serine-threonine protein kinase Rim15-encoding gene attenuated biotrophic growth, disrupted interfacial membrane integrity and abolished the in planta autophagic cycling we observe here for the first time in wild type. Δrim15 was also impaired for glutaminolysis and depleted for α-ketoglutarate. α-ketoglutarate treatment of Δrim15-infected leaf sheaths remediated Δrim15 biotrophic growth. In WT, α-ketoglutarate treatment suppressed autophagy. α-ketoglutarate signaling is amino acid prototrophy- and GS-GOGAT cycle-dependent. We conclude that, following initial IH elaboration, cycles of Rim15- dependent autophagic flux liberate α-ketoglutarate – via the GS-GOGAT cycle – as an amino acid-sufficiency signal to trigger TOR reactivation and promote fungal biotrophic growth in nutrient-restricted host rice cells.
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This content will become publicly available on November 25, 2025
Membrane fluidity control by the Magnaporthe oryzae acyl-CoA binding protein sets the thermal range for host rice cell colonization
Following leaf cuticle penetration by specialized appressorial cells, the devastating blast fungusMagnaporthe oryzaegrows as invasive hyphae (IH) in living rice cells. IH are separated from host cytoplasm by plant-derived membranes forming an apoplastic compartment and a punctate biotrophic interfacial complex (BIC) that mediate the molecular host-pathogen interaction. What molecular and cellular processes determine the temperature range for this biotrophic growth stage is an unanswered question pertinent to a broader understanding of how phytopathogens may cope with environmental stresses arising under climate change. Here, we shed light on thermal adaptation inM.oryzaeby disrupting theACB1gene encoding the single acyl-CoA-binding protein, an intracellular transporter of long-chain acyl-CoA esters. Loss ofACB1affected fatty acid desaturation levels and abolished pathogenicity at optimal (26°C) and low (22°C) but not elevated (29°C) infection temperatures (the latter following post-penetration shifts from 26°C). Relative to wild type, the Δacb1mutant strain exhibited poor vegetative growth and impaired membrane trafficking at 22°C and 26°C, but not at 29°C.In planta, Δacb1biotrophic growth was inhibited at 26°C–which was accompanied by a multi-BIC phenotype—but not at 29°C, where BIC formation was normal. Underpinning the Δacb1phenotype was impaired membrane fluidity at 22°C and 26°C but not at elevated temperatures, indicating Acb1 suppresses membrane rigidity at optimal- and suboptimal- but not supraoptimal temperatures. Deducing a temperature-dependent role for Acb1 in maintaining membrane fluidity homeostasis reveals how the thermal range for rice blast disease is both mechanistically determined and wider than hitherto appreciated.
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- Award ID(s):
- 2106153
- PAR ID:
- 10596502
- Editor(s):
- Thomma, Bart PHJ
- Publisher / Repository:
- Public Library of Science
- Date Published:
- Journal Name:
- PLOS Pathogens
- Volume:
- 20
- Issue:
- 11
- ISSN:
- 1553-7374
- Page Range / eLocation ID:
- e1012738
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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