The mitochondrial genome of the plant-pathogenic fungus Stemphylium lycopersici uncovers a dynamic structure due to repetitive and mobile elements.

Mario Emilio Ernesto Franco,Graciela Noemí Pastorino,Silvina Marianela Yanil López,Mario Carlos Nazareno Saparrat,Maria Inés Troncozo,César Gustavo Lucentini,Pedro Alberto Balatti,Rocio Medina,Marie-Joelle Virolle

doi:10.1371/journal.pone.0185545

Abstract

Stemphylium lycopersici (Pleosporales) is a plant-pathogenic fungus that has been associated with a broad range of plant-hosts worldwide. It is one of the causative agents of gray leaf spot disease in tomato and pepper. The aim of this work was to characterize the mitochondrial genome of S. lycopersici CIDEFI-216, to use it to trace taxonomic relationships with other fungal taxa and to get insights into the evolutionary history of this phytopathogen. The complete mitochondrial genome was assembled into a circular double-stranded DNA molecule of 75,911 bp that harbors a set of 37 protein-coding genes, 2 rRNA genes (rns and rnl) and 28 tRNA genes, which are transcribed from both sense and antisense strands. Remarkably, its gene repertoire lacks both atp8 and atp9, contains a free-standing gene for the ribosomal protein S3 (rps3) and includes 13 genes with homing endonuclease domains that are mostly located within its 15 group I introns. Strikingly, subunits 1 and 2 of cytochrome oxidase are encoded by a single continuous open reading frame (ORF). A comparative mitogenomic analysis revealed the large extent of structural rearrangements among representatives of Pleosporales, showing the plasticity of their mitochondrial genomes. Finally, an exhaustive phylogenetic analysis of the subphylum Pezizomycotina based on mitochondrial data reconstructed their relationships in concordance with several studies based on nuclear data. This is the first report of a mitochondrial genome belonging to a representative of the family Pleosporaceae.

Highlights

Stemphylium is a dematiaceous fungal genus belonging to the subphylum Pezizomycotina (Ascomycota)
The GC content of the protein-coding genes is quite similar to the overall GC content (29.1%), considerable deviations are found in the GC content of ribosomal RNA (rRNA) and transfer RNA (tRNA) genes, reaching 35% and 39%, respectively (Fig 1, Tables 1 and 2)
We found that the mitochondrial genome of S. lycopersici CIDEFI-216 lacks both atp8 and atp9 genes, which is in agreement with observations made in other representatives of Pleosporales

Summary

Introduction

Stemphylium (teleomorph: Pleospora) is a dematiaceous fungal genus belonging to the subphylum Pezizomycotina (Ascomycota). Species within this genus are widely distributed in nature, where they are found establishing pathogenic, saprotrophic or endophytic relationships with a broad range of plant hosts. Pathogenic representatives of this genus cause severe yield reductions and economic losses on several crops worldwide [1]. The whole-genome sequencing project of S. lycopersici CIDEFI-216 [11] might shed light on many of these issues and might contribute to a better understanding of the evolutionary history of Stemphylium

Objectives

Methods

Results

Conclusion