Alloplasmic male-sterile Brassica lines containing B. tournefortii mitochondria express an ORF 3? of the atp6 gene and a 32 kDa protein

Abstract

Analyses of mitochondrial transcription and in organello translation were performed with the Brassica tournefortii cytoplasm. This cytoplasm causes alloplasmic male sterility when combined with the nuclear genomes of B. napus and B. juncea. Mitochondrial RNA and protein banding patterns were compared between the fertile wild species B. tournefortii, an alloplasmic male-sterile B. juncea line, an alloplasmic male-sterile B. napus line and an alloplasmic B. napus line with restored fertility. The analyses were carried out to identify differences in gene expression and to investigate whether alterations in gene expression accompanied male sterility. A difference in transcription patterns between the fertile B. tournefortii and the alloplasmic lines was found for the atp6 gene. The atp6 region was investigated further, since a similar alteration in atp6 transcription has been observed in two other Brassica cytoplasms which are associated with cytoplasmic male sterility (CMS). The additional longer atp6 transcript detected in the alloplasmic lines in the present study was found to contain an open reading frame (ORF) located downstream of the atp6 gene. DNA sequencing revealed that the ORF, orf263, could encode a protein with a predicted molecular weight of about 29 kDa. In organello analysis detected two proteins of 29 and 32 kDa respectively, which were found only in the alloplasmic lines. Furthermore, the 32 kDa protein accompanied male sterility since it was absent in alloplasmic plants restored to fertility. The protein analysis might indicate that orf263 is translated and causes CMS.

Interactions of Mitochondrial and Nuclear Genes That Affect Male Gametophyte Development

“…Sequencing of the region near atp6 revealed a 263-codon orf gene containing 90 codons similar to nad5 exon a, followed by a 45-codon segment with similarity to a portion of the atp6 coding region (Figure 1). A 32-kD protein was observed in CMS but not in restored lines upon in organello protein synthesis (Landgren et al, 1996). Whether the orf263 gene encodes the 32-kD protein is not known.…”

“…When Brassica tournefortii cytoplasm is introgressed into either B. napus or B. juncea, the lines become CMS. Probing of RNA gel blots from B. napus (tour) CMS versus restored lines with 17 gene-specific probes revealed a longer atp6-hybridizing transcript in CMS versus restored lines (Landgren et al, 1996). Sequencing of the region near atp6 revealed a 263-codon orf gene containing 90 codons similar to nad5 exon a, followed by a 45-codon segment with similarity to a portion of the atp6 coding region (Figure 1).…”

Plant Mitochondrial Genome Evolution and Cytoplasmic Male Sterility

“…That is, in many CMS systems, RF genes do not affect accumulation of the CMS transcript; rather, restored lines are characterized by a marked decrease in toxic CMS protein accumulation (Chen and Liu, 2014). Reduced protein accumulation (without similar transcript reduction) has been observed in maize (Dewey et al, 1991), common bean (Sarria et al, 1998), Brassica (Landgren et al, 1996), radish (Uyttewaal et al, 2008), and rice (Itabashi et al, 2011), among others. Many of these suggest that restoration of fertility occurs via reduction in the production of toxic proteins; however, in at least one maize CMS system, there is evidence that fertility is restored via the degradation of toxic products (versus proteins; Liu et al, 2001).…”

Interspecific incompatibility in wide hybridization of plants and ways to overcome

“…Теоретически для образования алло-плазматических линий должны происходить два основных события: 1) замещение материнского ядерного генома на отцовский ядерный геном в процессе последовательных возвратных скрещиваний гибридов с отцовским видом; 2) эволюционно закрепленная передача органельных геномов по материнской линии (Tsunewaki, 1996). Алло-плазматические линии получены у разных видов Triticum (Tsunewaki, 1996), Allium cepa (Vu et al, 2011), Brassica napus (Landgren et al, 1996;Shinada et al, 2006), Nicotiana tabacum (Farbos et al, 2001) и других растений. В зависи-мости от ядерно-цитоплазматических комбинаций у ал-лоплазматических линий могут происходить нарушения клеточного развития, связанные с высокой частотой хро-мосомных аномалий в соматических клетках, приводящих к гибели клеток, подавлению роста и развития растений (Бадаева и др., 2006).…”