Deletion of the sex-determining gene SXI1\u03b1 enhances the spread of mitochondrial introns in Cryptococcus neoformans

Zhun Yan,Zhimin Li,Xiangping Sun,Yi Cheng,Yongting Yu,Li Yan,Jianping Xu,Chunsheng Gao,Yunyun Liu,Litao Guo,Jia Chen,Liangbin Zeng

doi:10.1186/s13100-018-0129-0

Zhun Yan, Zhimin Li + Show 10 more

Open Access

https://doi.org/10.1186/s13100-018-0129-0

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Abstract

BackgroundHoming endonuclease genes (HEGs) are widely distributed genetic elements in the mitochondrial genomes of a diversity of eukaryotes. Due to their ability to self-propagate within and between genomes, these elements can spread rapidly in populations. Whether and how such elements are controlled in genomes remains largely unknown.ResultsHere we report that the HEG-containing introns in the mitochondrial COX1 gene in Cryptococcus neoformans are mobile and that their spread in sexual crosses is influenced by mating type (MAT) α-specific homeodomain gene SXI1α. C. neoformans has two mating types, MATa and MATα. In typical crosses between strains of the two mating types, only a small portion (< 7%) of diploid fusants inherited the HEGs from the MATα parent. However, disruption of the SXI1α gene resulted in the majority (> 95%) of the diploid fusants inheriting the HEG-containing introns from the MATα parent, a frequency significantly higher than those of intronless mitochondrial genes.ConclusionsOur results suggest that SXI1α not only determines uniparental mitochondrial inheritance but also inhibits the spread of HEG-containing introns in the mitochondrial genome in C. neoformans.

Highlights

Homing endonuclease genes (HEGs) are widely distributed genetic elements in the mitochondrial genomes of a diversity of eukaryotes
The distribution of mitochondrial HEGs and their associated introns among the five parental strains Based on the published mitochondrial genome sequences, we synthesized primers to confirm the presence/absence of all mitochondrial introns in the five parental strains used in this study (Table 2)
Our analyses indicated that strains CHY618, CHY620, CHY647 and CHY648 had all the 10 introns described for the sequenced strains JEC21 and IFM5844, including five introns in the Cytochrome c oxidase I (COX1) gene, two each in the Cytochrome b (COB1) and large subunit of ribosomal RNA (LsrRNA) genes, and one in the

Summary

Introduction

Homing endonuclease genes (HEGs) are widely distributed genetic elements in the mitochondrial genomes of a diversity of eukaryotes. Due to their ability to self-propagate within and between genomes, these elements can spread rapidly in populations. HEGs are typically located in introns and are broadly distributed in all three Domains of life, including in both the nuclear and organelle genomes of all major groups of eukaryotes [1]. Despite their broad distribution, HEGs are not known to have any positive contribution to host fitness and function. The rapid spread of HEGs is achieved by a process termed “homing” which involves recognition and cutting of the HEG− allele by the HEG-encoded

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