Poster: Reproductive Development
Abs #
494: Identification and Transgenic Analysis of the Petunia Restorer of Fertility Locus
Petunia plants containing mitochondria encoding cytoplasmic male sterility (CMS) are fertile if they carry a single dominant nuclear gene (Rf, restorer of fertility). Rf alters the RNA- and protein-level expression of the CMS-associated mitochondrial pcf gene. The Rf locus was identified by positional cloning. Molecular markers linked to Rf were found by bulk segregant analysis, fine mapping, and physical mapping (Bentolila et al., Theor. Appl. Genet. 96:980-988, 1998). A petunia BIBAC library was constructed and screened with an Rf-linked AFLP marker, resulting in the identification of a 37.5 kb BIBAC clone that co-segregates with Rf (Bentolila and Hanson, Mol. Gen. Genet. 266:223-230, 2001). Shotgun sequencing of this clone revealed two highly similar candidate Rf genes, Rf-PPR592 and Rf-PPR591, both of which carry pentatricopeptide repeat (PPR) motifs. Several PPR-containing genes in maize and fungi are known to be involved in RNA processing and/or translation. An RF-PPR592 transit peptide-GFP fusion was localized to mitochondria in transient assays. Rf-PPR592 restored fertility in transgenic petunia plants (Bentolila et al., PNAS 99:10887-10892, 2002). Rf-PPR591 did not restore fertility, despite 93% protein-level similarity to Rf-PPR592. A homolog of Rf-PPR592 in the rf/rf line has a 94% similar coding region but exhibits a 530 nt deletion in the promoter region with respect to the Rf allele and is expressed in roots but not in floral tissues. A construct carrying the Rf promoter region and the rf coding region did not restore fertility. Expression of the Rf-PPR592 coding region under the control of a double 35S promoter resulted in abnormal vegetative and floral phenotypes. Supported by USDA NRI Plant Genome grants (98-35300-6171 and 01-35301-10565) to M.R.H.
