UMass Chan Medical School Faculty Publications

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Department of Biochemistry and Molecular Pharmacology

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Article Preprint


Cell and Developmental Biology | Fungi | Microbiology


The exocyst is a conserved multimeric complex that participates in the final steps of the secretion of vesicles. In the filamentous fungus Neurospora crassa, the exocyst is crucial for polar growth, morphology, and the organization of the Spitzenkörper (Spk), the apical body where secretory vesicles accumulate before being delivered to the plasma membrane. In the highly polarized cells of N. crassa, the exocyst subunits SEC-3, SEC-5, SEC-6, SEC-8, and SEC-15 were previously found localized at the plasma membrane of the cells’ apices, while EXO-70 and EXO-84 occupied the frontal outer layer of the Spk, occupied by vesicles. The localization of SEC-10 had remained so far elusive. In this work, SEC-10 was tagged with the green fluorescent protein (GFP) either at its N- or C-terminus and found localized at the plasma membrane of growing hyphal tips, similar to what was previously observed for some exocyst subunits. While expression of an N-terminally tagged version of SEC-10 at its native locus was fully viable, expression of a C-terminally tagged version at its native locus resulted in severe hyphal growth and polarity defects. Additionally, a sec-10 knockout mutant in a heterokaryotic state (with genetically different nuclei) was viable but showed a strongly aberrant phenotype, confirming that this subunit is essential to maintain hyphal morphogenesis. Transmission electron microscopy analysis revealed the lack of a Spk in the SEC-10-GFP strain, suggesting a critical role of the exocyst in the vesicular organization at the Spk. Mass spectrometry analysis revealed fewer peptides of exocyst subunits interacting with SEC-10-GFP than with GFP-SEC-10, suggesting an essential role of the C-terminus of SEC-10 in exocyst assembly and/or stability. Altogether, our data suggest that an unobstructed C-terminus of SEC-10 is indispensable for the exocyst complex function and that a GFP tag could be blocking important subunit-subunit interactions.


Exocyst, Neurospora crassa, mass spectrometry, SEC-10, Spitzenkörper

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bioRxiv 2022.01.14.475644; doi: Link to preprint on bioRxiv.


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Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.