Fungal Mitogenomes: Relevant Features to Planning Plant Disease Management

Abstract

Mitochondrial genomes (mt-genomes) are characterized by a distinct codon usage and their autonomous replication. Mt-genomes encode highly conserved genes (mt-genes), like proteins involved in electron transport and oxidative phosphorylation but they also carry highly variable regions that are in part responsible for their high plasticity. The degree of conservation of their genes is such that they allow the establishment of phylogenetic relationships even across distantly related species. Here, we describe the mechanisms that generate changes along mt-genomes, which play key roles at enlarging the ability of fungi to adapt to changing environments. Within mt-genomes of fungal pathogens, there are dispensable as well as indispensable genes for survival, virulence and/or pathogenicity. We also describe the different complexes or mechanisms targeted by fungicides, thus addressing a relevant issue regarding disease management. Despite the controversial origin and evolution of fungal mt-genomes, the intrinsic mechanisms and molecular biology involved in their evolution will help to understand, at the molecular level, the strategies for fungal disease management.

Keywords: fungal interactions; fungal mitogenome; mobile elements; pathogenesis; pathogens; plant disease management; virulence.

FIGURE 1

Mitochondrial components and the main features. I, II, and III (in red) schematic processes that lead to the size reduction of mitochondrial genome by gene loss.

FIGURE 2

Array and orientation of core genes, the untranslated genes of small and large ribosomal RNA subunits, and the AT/GC content of the circular mt-genome of Phlebia radiata (NC_020148, Basidiomycota) and the linear mt-genome of Synchytrium endobioticum (NC_042370, Chytridiomycota). Figure was made using OrganellarGenomeDRAW (OGDRAW) version 1.3.1 (Greiner et al., 2019).

FIGURE 3

Rhizoctonia solani mitochondrial genome and the type and number of introns present. The complete mt-genome is 235,849 bp long and encodes 15 conserved genes (showed in yellow). Group I introns are in red whereas group II are in blue. NCBI Reference Sequence: NC_021436.1. Figure was made using OrganellarGenomeDRAW (OGDRAW) version 1.3.1 (Greiner et al., 2019).

FIGURE 4

Scheme of gene conversion through intron invasion and mobility and diversification adapted from Wu and Hao (2019). SAE mechanisms, known as intronless homing is compared with intron homing mechanism (HEG). Intron homing is facilitated by intron-encoded endonuclease and occurs into homologous intron-minus genes. SAE occurs in adjacent intron-lacking genes and facilitate gene conversion of their neighboring genes. The horizontal lines indicate endonuclease site.