The Glyoxysomal Protease LON2 Is Involved in Fruiting-Body Development, Ascosporogenesis and Stress Resistance in Sordaria macrospora.

Antonia Werner,Leon M Hanke,Kolja Otte,Stefanie Pöggeler,Gertrud Stahlhut

doi:10.3390/jof7020082

Abstract

Microbodies, including peroxisomes, glyoxysomes and Woronin bodies, are ubiquitous dynamic organelles that play important roles in fungal development. The ATP-dependent chaperone and protease family Lon that maintain protein quality control within the organelle significantly regulate the functionality of microbodies. The filamentous ascomycete Sordaria macrospora is a model organism for studying fruiting-body development. The genome of S. macrospora encodes one Lon protease with the C-terminal peroxisomal targeting signal (PTS1) serine-arginine-leucine (SRL) for import into microbodies. Here, we investigated the function of the protease SmLON2 in sexual development and during growth under stress conditions. Localization studies revealed a predominant localization of SmLON2 in glyoxysomes. This localization depends on PTS1, since a variant without the C-terminal SRL motif was localized in the cytoplasm. A ΔSmlon2 mutant displayed a massive production of aerial hyphae, and produced a reduced number of fruiting bodies and ascospores. In addition, the growth of the ΔSmlon2 mutant was completely blocked under mild oxidative stress conditions. Most of the defects could be complemented with both variants of SmLON2, with and without PTS1, suggesting a dual function of SmLON2, not only in microbody, but also in cytosolic protein quality control.

Highlights

Published: 26 January 2021In fungi, microbodies comprise single membrane bound organelles, including peroxisomes, glyoxysomes and Woronin bodies, which play important roles during developmental processes [1,2]
We identified the Smlon2 gene coding for a glyoxysomal Lon protease with a C-terminal PTS1 targeting sequence in S. macrospora
We show that SmLON2 mainly localizes to microbodies and that this localization depends on the C-terminal PTS1

Summary

Introduction

Microbodies comprise single membrane bound organelles, including peroxisomes, glyoxysomes and Woronin bodies, which play important roles during developmental processes [1,2]. Woronin bodies are fungal specific organelles carrying mainly the HEX1 protein and are required for plugging of septal pores after wounding of hyphae [3,4]. Peroxisomes and glyoxysomes contain enzymes required for the catabolism of fatty acids (FA), biotin and secondary metabolite biosynthesis [2,5,6]. Folded proteins are imported into the lumen of microbodies when they possess a so-called peroxisomal targeting signal (PTS). These are short amino acid motifs found either at the C-terminus (PTS1), near the. PTS1 and PTS3 sequences are recognized by the cytoplasmic receptor Pex5p, while peroxisomal matrix proteins harboring PTS2 are recognized by the receptor Pex7p [5,6]

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