Intraspecific variations of the cytoplasmic male sterility genes orf108 and orf117 in Brassica maurorum and Moricandia arvensis, and the specificity of the mRNA processing

Abstract

The mitochondrial gene <i>orf108</i> co-transcribed with <i>atp1</i> and causes cytoplasmic male sterility in <i>Brassica</i> crops, is widely distributed across wild species and genera of <i>Brassicaceae</i>. However, intraspecific variations in the presence of <i>orf108</i> have not yet been studied, and the mechanisms for the wide distribution of the gene remain unclear. We analyzed the presence and sequence variations of <i>orf108</i> in two wild species, <i>Brassica maurorum</i> and <i>Moricandia arvensis</i>. After polymerase chain reaction amplification of the 5′ region of <i>atp1</i> and the coding sequence of <i>orf108</i>, we determined the DNA sequences. <i>B. maurorum</i> and <i>M. arvensis</i> showed variations for the presence of <i>orf108</i> or <i>orf117</i> (<i>orf108<sup>V117</sup></i>) both between and within accessions, and were not fixed to the mitochondrial type having the male sterile genes. Sequencing of the amplicons clarified that <i>B. maurorum</i> has <i>orf108<sup>V117</sup></i> instead of <i>orf108</i>. Sequencing also indicated mitochondrial heteroplasmy in the two species; particularly, in <i>B. maurorum</i>, one plant possessed both the <i>orf108</i> and <i>orf108<sup>V117</sup></i> sequences. The results suggested that substoichiometric shifting of the mitochondrial genomes leads to the acquisition or loss of <i>orf108</i>. Furthermore, fertility restorer genes of the two species were involved in the processing of the mRNA of the male sterility genes at different sites.

Identification and variation of a new restorer of fertility gene that induces cleavage in orf138 mRNA of Ogura male sterility in radish.

“…identi ed interspeci c mutations in the mitochondrial orf108 between Moricandia arvensis and Brassica oxyrrhina and observed that the Rf gene of M. arvensis that cleaved the orf108-atp1 transcript was rendered ineffective by the mutations. A similar effect of such mutations in orf108 on mRNA cleavage was also observed in Brassica maurorum(Yamagishi et al 2021b). However, the Rf gene against orf108 has not yet been identi ed, and thus, the molecular relationship between orf108 and the Rf genes is still unclear.…”

The mitochondrialorf117Shagene desynchronizes pollen development and causes pollen abortion in the Arabidopsis Sha CMS

“…Several features common to many, but not all, identified CMS-genes were drawn from the comparison of these genes (Hanson and Bentolila, 2004; Horn et al ., 2014; Chen et al ., 2017; Kitazaki et al ., 2023), and sometimes used to drive the search for mitochondrial CMS-causing genes: a chimeric sequence comprising identifiable parts of conserved mitochondrial genes and sequences of unknown origin; association and co-transcription with a conserved mitochondrial gene; expression profile modified by the action of nuclear Rf, most often at the RNA level; a predicted protein product containing hydrophobic transmembrane domain(s). While mitochondrial-CMS genes were first thought to be unique to a species or population, some were found to have evolved variants or related mitochondrial CMS genes within plant taxa, mainly in the Brassicaceae family (L’Homme et al ., 1997; Yamagishi and Terachi, 2001; Yamagishi et al ., 2021b, a ) and the rice genus (He et al ., 2020; Zhang et al ., 2022).…”