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Description

Polarized growth in filamentous fungi requires precise spatial and temporal coordination of kinase signaling. In the rice blast fungus Magnaporthe oryzae, the Nuclear Dbf2-related (NDR) kinase Cot1 is essential for hyphal polarity, appressorium morphogenesis, and normal invasive growth. However, the spatial and temporal regulation of Cot1 activity during polarized growth remains unclear. Using a fluorescence microscopy-based forward genetic screen, we identified mutant M41, which exhibits severe defects in polarized growth and malformed appressoria. Whole-genome sequencing revealed a missense mutation in COT1, encoding a conserved AGC-family kinase. Complementation with wild-type COT1 restored normal morphology and pathogenic development. Live-cell imaging demonstrates that Cot1 traffics bidirectionally along microtubules in a Hook1-dependent manner, consistent with localization to motile early endosomes that function as signaling platforms. In Cot1-deficient cells, the RNA-binding protein Gul1 fails to associate with early endosomes and instead accumulates in P-body-like inclusions, suggesting a role for Cot1 in coordinating kinase signaling with RNA transport and polarized growth.

To dissect Cot1 function with temporal precision, we are developing an analog-sensitive Cot1 allele by mutating the conserved gatekeeper residue within the ATP-binding pocket to render the kinase selectively susceptible to inhibition by the ATP analog 1-Naphthyl PP1. This chemical genetic approach will enable rapid and reversible control of Cot1 activity, allowing acute dissection of the spatial and dynamic requirements of NDR kinase signaling during fungal morphogenesis and pathogenicity.

Publication Date

4-30-2026

Keywords

Chemical Biology, Genetics, NDR Kinase Signaling, Fungus

Chemical Genetic Dissection of NDR Kinase Signaling During Polarized Growth in Magnaporthe oryzae

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