ARS | Publication request: Pentatricopeptide Repeat Genes in Onion (Allium cepa L.)

Submitted to: Plant and Animal Genome Conference
Publication Type: Abstract Only
Publication Acceptance Date: November 15, 2007
Publication Date: January 20, 2008
Citation: Melgar, S.A., Havey, M.J. 2008. Pentatricopeptide Repeat Genes in Onion (Allium cepa L.)[abstract]. Plant and Animal Genome Conference. p. 37.

Technical Abstract: Production of hybrid-onion seed depends on cytoplasmic-genic male sterility (CMS). The most commonly used CMS in onion requires the presence of male-sterile (S) cytoplasm and recessive alleles at one nuclear male-fertility restoration (Ms) locus. Male-sterile lines are seed propagated using maintainer lines, which possess normal (N) male-fertile cytoplasm and the homozygous recessive genotype at Ms. Because onion is a biennial, it takes at least 4 years of crossing to identify maintainers. Molecular markers have been identified that distinguish S and N cytoplasms and a single nucleotide polymorphism (AOB272) has been identified 0.9 cM from the Ms locus. Our goal is to clone Ms and develop a marker that can be scored without regard to recombination. Nuclear restorers cloned from other plants often carry pentatricopeptide repeats (PPRs), which are 35 degenerated amino-acid motifs tandemly arranged in proteins. There are three types of PPRs, the classical “P” motif, and less commonly the “L” and the “S” motifs. There are 466 PPR proteins in Arabidopsis with either the “P” or a combination of “PLS” motifs. Some “PLS” proteins have the “E”, “E+” and “DYW” motifs at their carboxy terminus. We evaluated EST and genomic sequences of onion and identified 39 different PPR genes. Nine belong to the “PLS” subfamily and 30 to the “P” subfamily. There were no significance differences for the number of proteins with PPRs, “E” and “DYW” motifs in onion, Arabidopsis, and rice (p=0.1714).