Abstract
Peroxisomes are present ubiquitously and make important contributions to cellular metabolism in eukaryotes. They play crucial roles in pathogenicity of plant fungal pathogens. The peroxisomal matrix proteins and peroxisomal membrane proteins (PMPs) are synthesized in the cytosol and imported post-translationally. Although the peroxisomal import machineries are generally conserved, some species-specific features were found in different types of organisms. In phytopathogenic fungi, the pathways of the matrix proteins have been elucidated, while the import machinery of PMPs remains obscure. Here, we report that MoPEX19, an ortholog of ScPEX19, was required for PMPs import and peroxisomal maintenance, and played crucial roles in metabolism and pathogenicity of the rice blast fungus Magnaporthe oryzae. MoPEX19 was expressed in a low level and Mopex19p was distributed in the cytoplasm and newly formed peroxisomes. MoPEX19 deletion led to mislocalization of peroxisomal membrane proteins (PMPs), as well peroxisomal matrix proteins. Peroxisomal structures were totally absent in Δmopex19 mutants and woronin bodies also vanished. Δmopex19 exhibited metabolic deficiency typical in peroxisomal disorders and also abnormality in glyoxylate cycle which was undetected in the known mopex mutants. The Δmopex19 mutants performed multiple disorders in fungal development and pathogenicity-related morphogenesis, and lost completely the pathogenicity on its hosts. These data demonstrate that MoPEX19 plays crucial roles in maintenance of peroxisomal and peroxisome-derived structures and makes more contributions to fungal development and pathogenicity than the known MoPEX genes in the rice blast fungus.
Highlights
Peroxisomes are ubiquitously present in eukaryotic cells, and typically consist of a protein-rich matrix surrounded by a single membrane
We characterized MoPEX19, an essential factor in peroxisomal biogenesis, and demonstrated that Mopex19p was indispensable for peroxisomal membrane proteins (PMPs) targeting and maintenance of the peroxisomes, and was required in the pathogenicity and multiple developmental processes of the rice blast fungus M. oryzae
Role of MoPEX19 in peroxisomal membrane biogenesis the involvement of PEX19 in peroxisomal membranes biogenesis was well demonstrated in mammalian and yeast models [21,47], the functions of PEX19 are poorly understood in filamentous fungi
Summary
Peroxisomes are ubiquitously present in eukaryotic cells, and typically consist of a protein-rich matrix surrounded by a single membrane. They are involved in various metabolic processes, such as H2O2 metabolism and fatty acid b-oxidation, and some organism-specific biochemical reactions, such as the synthesis of cholesterol, bile acids and plasminogen in mammals, the glyoxylate cycle in plants, and methanol oxidation in yeast [1]. The biogenesis of peroxisomes originates in the endoplasmic reticulum (ER) and consists of: (i) formation of the peroxisome membrane including acquisition of integral peroxisomal membrane proteins (PMPs); (ii) import of peroxisomal matrix proteins; and (iii) peroxisome proliferation [4]. The proteins involved in peroxisomal import are designated as peroxins and their encoding genes are written as PEX [6]. Homologues of most PEX genes are present in filamentous fungi [7,8,9,10]
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