Comparative Analysis of Four Calypogeia Species Revealed Unexpected Change in Evolutionarily-Stable Liverwort Mitogenomes.

Monika Ślipiko,Katarzyna Buczkowska-Chmielewska,Alina Bączkiewicz,Monika Szczecińska,Kamil Myszczyński,Jakub Sawicki

doi:10.3390/genes8120395

Monika Ślipiko, Katarzyna Buczkowska-Chmielewska + Show 4 more

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https://doi.org/10.3390/genes8120395

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Abstract

Liverwort mitogenomes are considered to be evolutionarily stable. A comparative analysis of four Calypogeia species revealed differences compared to previously sequenced liverwort mitogenomes. Such differences involve unexpected structural changes in the two genes, cox1 and atp1, which have lost three and two introns, respectively. The group I introns in the cox1 gene are proposed to have been lost by two-step localized retroprocessing, whereas one-step retroprocessing could be responsible for the disappearance of the group II introns in the atp1 gene. These cases represent the first identified losses of introns in mitogenomes of leafy liverworts (Jungermanniopsida) contrasting the stability of mitochondrial gene order with certain changes in the gene content and intron set in liverworts.

Highlights

Group I and group II introns, next to spliceosomal and transfer RNA introns, belong to four main types of introns divided on the basis of splicing mechanism [1]. two transesterification reactions are used by group I and group II introns for their splicing, the reaction mechanisms are different
The structure of the Calypogeia mitogenome is in line with reports of the stability of mitochondrial genomes in bryophyte lineages
The gene order is identical to other liverworts, while gene content fits the patterns that emerged in liverwort evolution

Summary

Introduction

Group I and group II introns, next to spliceosomal and transfer RNA (tRNA) introns, belong to four main types of introns divided on the basis of splicing mechanism [1]. two transesterification reactions are used by group I and group II introns for their splicing, the reaction mechanisms are different. Group I introns are removed in a linear form, and some of them can circularize, whereas group II introns are released as a lariat [2]. Both discussed intron groups are known as mobile elements. Their mobility is possible thanks to internal encoded enzymes, but the movement mechanism in each of the groups is different. Group I introns can proliferate by a DNA-mediated homing mechanism, where intron-encoded endonucleases play a key role. Retrohoming (RNA-mediated mechanism) is used by group II introns for propagation [3]. Internal encoded enzymes of this intron class, maturase, reverse transcriptase and endonuclease, enable retrohoming [4]

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