The largest mitochondrial genome from a fungal pathogen

Background

Mitochondria are organelles that perform critical functions in most eukaryotic cells. They are particularly important for fungi because mutations in the mtDNA are often associated with resistance to fungicides that block the electron transport chain. The mitochondrial genomes for many fungal species have been sequenced. However, there was a lack a mtDNA resources for powdery mildew fungi.

However, an unanswered question question was:

Major findings

By obtaining and comparing the mitochondrial genomes of four powdery mildew fungi, I found that they have a similar gene content but a large variation in size, from 109 kb in Blumeria graminis to 332 kb in Golovinomyces cichoracearum, which is the largest mitochondrial genome among fungal pathogens reported to date. The large size variation is mostly because of the presence of long introns. An extreme example is the gene cytochrome b (cob), which has a single intron in B. graminis, but an outstanding 13 introns in G. cichoracearum. The reason for such high variation in intron content is unknown. However, one explanation is that introns are rapid gain and lost

More details and other findings are described in Zaccaron and Stergiopoulos 2021.