Altered Transcript Reveals an Orf507 Sterility-Related Gene in Chili Pepper (Capsicum annuum L.)

Abstract

A previously reported cytoplasmic male sterilityassociated fragment was detected in chili pepper (Capsicum annuum L.) and sequenced in the mitochondria of a sterile plant. This fragment, 16 kb in size, contains two common mitochondrial genes, coxII and atp6-2, and the newly detected gene orf456, which appears to be a strong candidate gene for the male sterile phenotype. The data show that one nucleotide (Cytosine) at the +449 position is missing compared with the original sequence data of orf456. By translation to the amino acid sequence, the termination codon was found 49 nt downstream from the original site. This hypothetical extension was confirmed by RT-PCR, which showed a sequence size of 507 bp. Since pollen fertility can be restored by a nuclear restorer of fertility gene (Rf), the transcription of orf507 was checked in four stages of flower development. The RT-PCR resulted in a fragment in stage III in the restorer line, indicating a possible role in microspore development.

Mitochondrial Cytochrome c Oxidase and F1Fo-ATPase Dysfunction in Peppers (Capsicum annuum L.) with Cytoplasmic Male Sterility and Its Association with orf507 and Ψatp6-2 Genes

“…Kim et al [35] and Gulyas et al [6] found that orf507 and the Ψatp6-2 [36] are associated with pollen formation in the pepper CMS line. Within the CMS line, orf507 , which is a novel ORF at the 3′-end of the cox II gene, is co-transcribed with cox II, and Ψatp6-2 is a pseudogene that is truncated at the C -terminal coding region when compared with the normal atp6-2 from the maintainer line.…”

“…In many cases, this characteristic is a consequence of intermolecular rearrangements in the mitochondrial DNA, which produce many novel open reading frames (ORFs) that are co-transcribed with conventional mitochondrial genes [2]. Many ORFs that are associated with CMS have been identified, such as orf239 in the common bean [3], pcf in petunia [4], orf507 in pepper [5,6], orfB in Brassica juncea [7], orfH522 in sunflower [8], orfH79 [9] and orfZ79 [10] in rice, to name a few. CMS phenotypes can also be induced by the differential expression of mitochondrial genes under the influence of various nuclear backgrounds [11] or due to the absence of RNA editing, as in atp9 of wheat [12], and a substoichiometric copy number of a chimeric gene.…”

“…In pepper, the CMS cytoplasm was first isolated from an Indian C. annuum accession (PI164835) [34]. The candidate genes orf456 or orf507 and Ψatp6-2 have been identified in CMS pepper [5,6,35]. The orf456 gene, which is co-transcribed with the coxII gene that encodes a subunit of cytochrome c oxidase in mitochondria, can induce male sterility in Arabidopsis thaliana , at least when it is over-expressed [35].…”

“…The orf456 gene, which is co-transcribed with the coxII gene that encodes a subunit of cytochrome c oxidase in mitochondria, can induce male sterility in Arabidopsis thaliana , at least when it is over-expressed [35]. Gulyas [6] found that because of the deletion (cytosine, C), the original stop codon of orf456 changed to asparagine (N), so the translated fragment was extended, ending with a new termination codon, giving a total length of 507 bp, named orf507 . The Ψatp6-2 is a 3′-truncated form of wild-type atp6-2 , which encodes a subunit of F 1 F o -ATP synthase in normal cytoplasm [36].…”

Plant Mitochondrial Genome Evolution and Cytoplasmic Male Sterility

“…Novel and chimeric mitochondrial sequences are a frequent result of this recombination (Wise et al, 1987;Kennell and Pring, 1989;Wen and Chase, 1999;Gallagher et al, 2002;Okazaki et al, 2013;Yamagishi and Bhat, 2014;Tang et al, 2017), in which recombination sometimes leads to the creation of transcripts that interfere with normal male gametophyte development (Kitazaki and Kubo, 2010) via the generation of toxic and/or disruptive transmembrane proteins (Korth et al, 1991;Kim et al, 2007;Wan et al, 2007;Zhang et al, 2007;Yang et al, 2009;Gulyas et al, 2010;Jing et al, 2012;Flores-Renteria et al, 2013;Ji et al, 2013;Luo et al, 2013;Okazaki et al, 2013;Park et al, 2013;Hu et al, 2014). Surprisingly, such genes are not only abundant in many fertile plants, such as Arabidopsis thaliana Unseld et al, 1997), Beta vulgaris (Kubo et al, 2000), Oryza sativa (Notsu et al, 2002), Brassica napus (Handa, 2003), Zea mays (Clifton et al, 2004), Triticum aestivum (Ogihara et al, 2005), and Nicotiana tabacum (Sugiyama et al, 2005), but are also constitutively expressed.…”