GELLIN PROTEINS: FLOW INDUCED CYTOPLASMIC CLOTTING IN WOUNDED FUNGAL HYPHAE

Abstract

Bulk transport of nutrients and signalling molecules through interconnected networks enables long-range communication and labour division, which are key features of multicellular organisms. To minimize the loss of valuable resources following injuries, animals, plants and fungi have evolved different strategies to conditionally restrict this interconnectivity. Wound response in septate filamentous fungi involves septal pore plugging by membrane-bound organelles. In the Mucorales, actively growing hyphae are aseptate and their response to mechanical injuries is unclear. We showed that wounding in the Mucorales results in explosive cytoplasmic discharge and clotting within milliseconds. We identified Mucorales-specific Gellin proteins as effectors of this response. Gellins encode an N-terminal array of ten Gll domains, some of which bind and crosslink membranous organelles, while others are sensitive to flow stress and have low mechanical stability. In cell-free reconstitution, concatenated Gll domains form large aggregates that incorporate membranous organelles when subject to flow stress. Taken together, these data identify the clotting effectors and define a mechanistic basis for cytoplasmic clotting, which is a key adaptation in the evolution of the filamentous Mucorales.