Two KTR Mannosyltransferases Are Responsible for the Biosynthesis of Cell Wall Mannans and Control Polarized Growth in <italic toggle="yes">Aspergillus fumigatus</italic>

ABSTRACT Fungal cell wall mannans are complex carbohydrate polysaccharides with different structures in yeasts and molds. In contrast to yeasts, their biosynthetic pathway has been poorly investigated in filamentous fungi. In Aspergillus fumigatus, the major mannan structure is a galactomannan that...

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Autores principales:	Christine Henry, Jizhou Li, François Danion, Laura Alcazar-Fuoli, Emilia Mellado, Rémi Beau, Grégory Jouvion, Jean-Paul Latgé, Thierry Fontaine
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2019
Materias:	Aspergillus fumigatus galactomannan KTR mannosyltransferase biosynthesis cell wall Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/037df80d565e4077a0e1b1dff7e14e81
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spelling	oai:doaj.org-article:037df80d565e4077a0e1b1dff7e14e812021-11-15T15:55:14ZTwo KTR Mannosyltransferases Are Responsible for the Biosynthesis of Cell Wall Mannans and Control Polarized Growth in <italic toggle="yes">Aspergillus fumigatus</italic>10.1128/mBio.02647-182150-7511https://doaj.org/article/037df80d565e4077a0e1b1dff7e14e812019-02-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.02647-18https://doaj.org/toc/2150-7511ABSTRACT Fungal cell wall mannans are complex carbohydrate polysaccharides with different structures in yeasts and molds. In contrast to yeasts, their biosynthetic pathway has been poorly investigated in filamentous fungi. In Aspergillus fumigatus, the major mannan structure is a galactomannan that is cross-linked to the β-1,3-glucan-chitin cell wall core. This polymer is composed of a linear mannan with a repeating unit composed of four α1,6-linked and α1,2-linked mannoses with side chains of galactofuran. Despite its use as a biomarker to diagnose invasive aspergillosis, its biosynthesis and biological function were unknown. Here, we have investigated the function of three members of the Ktr (also named Kre2/Mnt1) family (Ktr1, Ktr4, and Ktr7) in A. fumigatus and show that two of them are required for the biosynthesis of galactomannan. In particular, we describe a newly discovered form of α-1,2-mannosyltransferase activity encoded by the KTR4 gene. Biochemical analyses showed that deletion of the KTR4 gene or the KTR7 gene leads to the absence of cell wall galactomannan. In comparison to parental strains, the Δktr4 and Δktr7 mutants showed a severe growth phenotype with defects in polarized growth and in conidiation, marked alteration of the conidial viability, and reduced virulence in a mouse model of invasive aspergillosis. In yeast, the KTR proteins are involved in protein 0- and N-glycosylation. This study provided another confirmation that orthologous genes can code for proteins that have very different biological functions in yeasts and filamentous fungi. Moreover, in A. fumigatus, cell wall mannans are as important structurally as β-glucans and chitin. IMPORTANCE The fungal cell wall is a complex and dynamic entity essential for the development of fungi. It allows fungal pathogens to survive environmental challenge posed by nutrient stress and host defenses, and it also is central to polarized growth. The cell wall is mainly composed of polysaccharides organized in a three-dimensional network. Aspergillus fumigatus produces a cell wall galactomannan whose biosynthetic pathway and biological functions remain poorly defined. Here, we described two new mannosyltransferases essential to the synthesis of the cell wall galactomannan. Their absence leads to a growth defect with misregulation of polarization and altered conidiation, with conidia which are bigger and more permeable than the conidia of the parental strain. This study showed that in spite of its low concentration in the cell wall, this polysaccharide is absolutely required for cell wall stability, for apical growth, and for the full virulence of A. fumigatus.Christine HenryJizhou LiFrançois DanionLaura Alcazar-FuoliEmilia MelladoRémi BeauGrégory JouvionJean-Paul LatgéThierry FontaineAmerican Society for MicrobiologyarticleAspergillus fumigatusgalactomannanKTRmannosyltransferasebiosynthesiscell wallMicrobiologyQR1-502ENmBio, Vol 10, Iss 1 (2019)
institution	DOAJ
collection	DOAJ
language	EN
topic	Aspergillus fumigatus galactomannan KTR mannosyltransferase biosynthesis cell wall Microbiology QR1-502
spellingShingle	Aspergillus fumigatus galactomannan KTR mannosyltransferase biosynthesis cell wall Microbiology QR1-502 Christine Henry Jizhou Li François Danion Laura Alcazar-Fuoli Emilia Mellado Rémi Beau Grégory Jouvion Jean-Paul Latgé Thierry Fontaine Two KTR Mannosyltransferases Are Responsible for the Biosynthesis of Cell Wall Mannans and Control Polarized Growth in <italic toggle="yes">Aspergillus fumigatus</italic>
description	ABSTRACT Fungal cell wall mannans are complex carbohydrate polysaccharides with different structures in yeasts and molds. In contrast to yeasts, their biosynthetic pathway has been poorly investigated in filamentous fungi. In Aspergillus fumigatus, the major mannan structure is a galactomannan that is cross-linked to the β-1,3-glucan-chitin cell wall core. This polymer is composed of a linear mannan with a repeating unit composed of four α1,6-linked and α1,2-linked mannoses with side chains of galactofuran. Despite its use as a biomarker to diagnose invasive aspergillosis, its biosynthesis and biological function were unknown. Here, we have investigated the function of three members of the Ktr (also named Kre2/Mnt1) family (Ktr1, Ktr4, and Ktr7) in A. fumigatus and show that two of them are required for the biosynthesis of galactomannan. In particular, we describe a newly discovered form of α-1,2-mannosyltransferase activity encoded by the KTR4 gene. Biochemical analyses showed that deletion of the KTR4 gene or the KTR7 gene leads to the absence of cell wall galactomannan. In comparison to parental strains, the Δktr4 and Δktr7 mutants showed a severe growth phenotype with defects in polarized growth and in conidiation, marked alteration of the conidial viability, and reduced virulence in a mouse model of invasive aspergillosis. In yeast, the KTR proteins are involved in protein 0- and N-glycosylation. This study provided another confirmation that orthologous genes can code for proteins that have very different biological functions in yeasts and filamentous fungi. Moreover, in A. fumigatus, cell wall mannans are as important structurally as β-glucans and chitin. IMPORTANCE The fungal cell wall is a complex and dynamic entity essential for the development of fungi. It allows fungal pathogens to survive environmental challenge posed by nutrient stress and host defenses, and it also is central to polarized growth. The cell wall is mainly composed of polysaccharides organized in a three-dimensional network. Aspergillus fumigatus produces a cell wall galactomannan whose biosynthetic pathway and biological functions remain poorly defined. Here, we described two new mannosyltransferases essential to the synthesis of the cell wall galactomannan. Their absence leads to a growth defect with misregulation of polarization and altered conidiation, with conidia which are bigger and more permeable than the conidia of the parental strain. This study showed that in spite of its low concentration in the cell wall, this polysaccharide is absolutely required for cell wall stability, for apical growth, and for the full virulence of A. fumigatus.
format	article
author	Christine Henry Jizhou Li François Danion Laura Alcazar-Fuoli Emilia Mellado Rémi Beau Grégory Jouvion Jean-Paul Latgé Thierry Fontaine
author_facet	Christine Henry Jizhou Li François Danion Laura Alcazar-Fuoli Emilia Mellado Rémi Beau Grégory Jouvion Jean-Paul Latgé Thierry Fontaine
author_sort	Christine Henry
title	Two KTR Mannosyltransferases Are Responsible for the Biosynthesis of Cell Wall Mannans and Control Polarized Growth in <italic toggle="yes">Aspergillus fumigatus</italic>
title_short	Two KTR Mannosyltransferases Are Responsible for the Biosynthesis of Cell Wall Mannans and Control Polarized Growth in <italic toggle="yes">Aspergillus fumigatus</italic>
title_full	Two KTR Mannosyltransferases Are Responsible for the Biosynthesis of Cell Wall Mannans and Control Polarized Growth in <italic toggle="yes">Aspergillus fumigatus</italic>
title_fullStr	Two KTR Mannosyltransferases Are Responsible for the Biosynthesis of Cell Wall Mannans and Control Polarized Growth in <italic toggle="yes">Aspergillus fumigatus</italic>
title_full_unstemmed	Two KTR Mannosyltransferases Are Responsible for the Biosynthesis of Cell Wall Mannans and Control Polarized Growth in <italic toggle="yes">Aspergillus fumigatus</italic>
title_sort	two ktr mannosyltransferases are responsible for the biosynthesis of cell wall mannans and control polarized growth in <italic toggle="yes">aspergillus fumigatus</italic>
publisher	American Society for Microbiology
publishDate	2019
url	https://doaj.org/article/037df80d565e4077a0e1b1dff7e14e81
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Two KTR Mannosyltransferases Are Responsible for the Biosynthesis of Cell Wall Mannans and Control Polarized Growth in <italic toggle="yes">Aspergillus fumigatus</italic>

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