The GUL-1 Protein Binds Multiple RNAs Involved in Cell Wall Remodeling and Affects the MAK-1 Pathway in Neurospora crassa.

Inbal Herold,Zheng Wang,Avihai Zolti,Francesc López-Giráldez,Rosa R Mouriño-Pérez,Jeffrey P Townsend,Igor Ulitsky,Marisela Garduño-Rosales,Oded Yarden

doi:10.3389/ffunb.2021.672696

Abstract

The Neurospora crassa GUL-1 is part of the COT-1 pathway, which plays key roles in regulating polar hyphal growth and cell wall remodeling. We show that GUL-1 is a bona fide RNA-binding protein (RBP) that can associate with 828 "core" mRNA species. When cell wall integrity (CWI) is challenged, expression of over 25% of genomic RNA species are modulated (2,628 mRNAs, including the GUL-1 mRNA). GUL-1 binds mRNAs of genes related to translation, cell wall remodeling, circadian clock, endoplasmic reticulum (ER), as well as CWI and MAPK pathway components. GUL-1 interacts with over 100 different proteins, including stress-granule and P-body proteins, ER components and components of the MAPK, COT-1, and STRIPAK complexes. Several additional RBPs were also shown to physically interact with GUL-1. Under stress conditions, GUL-1 can localize to the ER and affect the CWI pathway-evident via altered phosphorylation levels of MAK-1, interaction with mak-1 transcript, and involvement in the expression level of the transcription factor adv-1. We conclude that GUL-1 functions in multiple cellular processes, including the regulation of cell wall remodeling, via a mechanism associated with the MAK-1 pathway and stress-response.

Highlights

The Neurospora crassa GUL-1 protein (NCU01197) is a component of the COT-1 (Colonial Temperature sensitive 1; NCU07296.7) NDR-kinase pathway (Herold et al, 2019)
To identify potential GUL-1-interacting transcripts, we scanned the N. crassa transcriptome with a 5′-UTR motif, A[G/U]UCAUUCCUU, identified in some of the S. cerevisiae mRNAs that interact with Ssd1 (Hogan et al, 2008; Wanless et al, 2014)
In the presence of Nikkomycin Z, we found that 46 of the 81 proteins bound to GUL-1 had corresponding mRNAs that were identified as associated with the RNA-binding protein (RBP)

Summary

Introduction

The Neurospora crassa GUL-1 protein (NCU01197) is a component of the COT-1 (Colonial Temperature sensitive 1; NCU07296.7) NDR-kinase pathway (Herold et al, 2019). The components of this pathway play key roles in regulating cell wall remodeling and polar growth, fundamental processes of filamentous fungi (Yarden et al, 1992; Gorovits et al, 2000; Gorovits and Yarden, 2003; Maerz and Seiler, 2010; Ziv et al, 2013; Herold and Yarden, 2017). Overexpression of ssdA increases chitin levels; loss and overexpression of ssdA alter the localization of the A. fumigatus chitin-synthase CsmA (Thammahong et al, 2019)

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Conclusion