||Post-translational mechanisms are associated with fertility restoration of cytoplasmic male sterility in sugar beet
Kitazaki, Kazuyoshi ,
Arakawa, Takumi ,
Matsunaga, Muneyuki ,
Yui-Kurino, Rika ,
Matsuhira, Hiroaki Mikami, Tetsuo ,
299 , 2015-07-04 , Wiley-blackwell
Genetic conflict between cytoplasmically inherited elements and nuclear genes due to 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 ORF 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 having 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 sugar beet bvORF20, a non-PPR Rf, with preSatp6, the sugar beet S-orf. Anthers expressing bvORF20 contained a protein that interacted with preSATP6 protein. Analysis of anthers and transgenic calli expressing a FLAG-tagged bvORF20 suggested binding of preSATP6 to bvORF20. To see the effect of bvORF20 on preSATP6, 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 likely includes 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.