Abstract
Powdery mildews are notorious fungal plant pathogens but only limited information exists on their genomes. Here we present the mitochondrial genome of the grape powdery mildew fungus Erysiphe necator and a high-quality mitochondrial gene annotation generated through cloning and Sanger sequencing of full-length cDNA clones. The E. necator mitochondrial genome consists of a circular DNA sequence of 188,577 bp that harbors a core set of 14 protein-coding genes that are typically present in fungal mitochondrial genomes, along with genes encoding the small and large ribosomal subunits, a ribosomal protein S3, and 25 mitochondrial-encoded transfer RNAs (mt-tRNAs). Interestingly, it also exhibits a distinct gene organization with atypical bicistronic-like expression of the nad4L/nad5 and atp6/nad3 gene pairs, and contains a large number of 70 introns, making it one of the richest in introns mitochondrial genomes among fungi. Sixty-four intronic ORFs were also found, most of which encoded homing endonucleases of the LAGLIDADG or GIY-YIG families. Further comparative analysis of five E. necator isolates revealed 203 polymorphic sites, but only five were located within exons of the core mitochondrial genes. These results provide insights into the organization of mitochondrial genomes of powdery mildews and represent valuable resources for population genetic and evolutionary studies.
Highlights
Powdery mildews are notorious fungal plant pathogens but only limited information exists on their genomes
We present a high-quality mt genome for E. necator, an economically important powdery mildew pathogen, and provide further insights into the mt genome organization of members of the Erysiphales
Our analysis showed that the mt genome of E. necator is large but compact with dozens of group I introns encoding mostly homing endonucleases (HEs) from the LAGLIDADG and GIY-YIG families
Summary
Powdery mildews are notorious fungal plant pathogens but only limited information exists on their genomes. The E. necator mitochondrial genome consists of a circular DNA sequence of 188,577 bp that harbors a core set of 14 protein-coding genes that are typically present in fungal mitochondrial genomes, along with genes encoding the small and large ribosomal subunits, a ribosomal protein S3, and 25 mitochondrial-encoded transfer RNAs (mt-tRNAs). Mt genomes contain a standard set of 14 core genes (i.e., atp, atp, atp, nad, nad, nad, nad, nad4L, nad, nad, cob, cox, cox, and cox3) that encode proteins involved in the electron transport chain (ETC) and oxidative p hosphorylation9 They harbor two genes encoding the small and large ribosomal subunits (rns and rnl, respectively) and a set of mt-encoded transfer RNAs (mt-tRNAs). Some commonalities in gene arrangements exist as well, as for example is the case for the gene pairs nad4L/nad and nad2/nad, which appear next to each other in the mt genomes of most fungal species
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