Post‐translational mechanisms are associated with fertility restoration of cytoplasmic male sterility in sugar beet (Beta vulgaris)

Abstract

SUMMARYGenetic conflict between cytoplasmically inherited elements and nuclear genes arising from their different transmission patterns can be seen in cytoplasmic male sterility (CMS), the mitochondrion-encoded inability to shed functional pollen. CMS is associated with a mitochondrial open reading frame (ORF) that is absent from non-sterility inducing mitochondria (S-orf). Nuclear genes that suppress CMS are called restorer-of-fertility (Rf) genes. Post-transcriptional and translational repression of S-orf mediates the molecular action of Rf that encodes a class of RNA-binding proteins with pentatricopeptide repeat (PPR) motifs. Besides the PPR-type of Rfs, there are also non-PPR Rfs, but the molecular interactions between non-PPR Rf and S-orf have not been described. In this study, we investigated the interaction of bvORF20, a non-PPR Rf from sugar beet (Beta vulgaris), with preSatp6, the S-orf from sugar beet. Anthers expressing bvORF20 contained a protein that interacted with preSATP6 protein. Analysis of anthers and transgenic calli expressing a FLAGtagged bvORF20 suggested the binding of preSATP6 to bvORF20. To see the effect of bvORF20 on pre-SATP6, which exists as a 250-kDa protein complex in CMS plants, signal bands of preSATP6 in bvORF20-expressing and non-expressing anthers were compared by immunoblotting combined with Blue Native polyacrylamide gel electrophoresis. The signal intensity of the 250-kDa band decreased significantly, and 200-and 150-kDa bands appeared in bvORF20-expressing anthers. Transgenic callus expressing bvORF20 also generated the 200-and 150-kDa bands. The 200-kDa complex is likely to include both preSATP6 and bvORF20. Post-translational interaction between preSATP6 and bvORF20 appears to alter the higher order structure of preSATP6 that may lead to fertility restoration in sugar beet.

In-silicoidentification of candidate genes for fertility restoration in cytoplasmic male sterile perennial ryegrass (Lolium perenneL.)

“…Exceptions are the CMS-T restoration in maize (Cui et al. 1996), the restorer of fertility ( Rf ) gene bvORF20 in sugar beet (Kitazaki et al. 2015) as well as other RNA-binding proteins that have been implicated in fertility restoration (Itabashi et al.…”

Efficient callus formation and plant regeneration are heritable characters in sugar beet (Beta vulgaris L.)

“…These attributes enabled us to develop an Agrobacterium -mediated transformation system for sugar beet [3, 4]. Using this system, molecular analyses of several genes have been completed [5–7]. On the other hand, the shortcomings of NK-219mm-O include its vernalization requirement, i.e.…”

Plant Mitochondrial Genome Evolution and Cytoplasmic Male Sterility

“…These are encoded not by the mitochondria, but by sequences in the nuclear genome. That is, sterility is reversed through synergistic cytonuclear interactions and antero/retrograde signaling between the mitochondrial and nuclear genomes (Rhoads and Subbaiah, 2007;Chen and Liu, 2014;Kitazaki et al, 2015;Liu et al, 2016). The exact nature of many of these RF loci, however, remains unknown.…”

“…Remarkably, many of the properties of the RF loci remain unknown. However, the coding capacity for those that are known (or can be predicted) are quite diverse, from an aldehyde dehydrogenase in maize (the first isolated plant restorer gene, Cui et al, 1996;Liu et al, 2001) to a putative peptidase in sugar beet (Matsuhira et al, 2012) to a suite of PPR proteins in diverse species (Brown et al, 2003;Kazama and Toriyama, 2003;Koizuka et al, 2003;Akagi et al, 2004;Komori et al, 2004;Klein et al, 2005;Wang et al, 2006;Uyttewaal et al, 2008;Jordan et al, 2010;Hu et al, 2012;Wang et al, 2013c;Kitazaki et al, 2015;Liu et al, 2016).…”