Unique aspects of cytoplasmic male sterility and fertility restoration in Brassica napus

Authors
Citation
Gg. Brown, Unique aspects of cytoplasmic male sterility and fertility restoration in Brassica napus, J HEREDITY, 90(3), 1999, pp. 351-356
Citations number
29
Categorie Soggetti
Biology,"Molecular Biology & Genetics
Journal title
JOURNAL OF HEREDITY
ISSN journal
00221503 → ACNP
Volume
90
Issue
3
Year of publication
1999
Pages
351 - 356
Database
ISI
SICI code
0022-1503(199905/06)90:3<351:UAOCMS>2.0.ZU;2-M
Abstract
Two male sterile cytoplasms, nap and pol, are found in the oilseed rape spe cies Brassica napus. As with many other forms of cytoplasmic male sterility (CMS), the mtDNA regions implicated in specifying the two forms of male st erility contain novel open reading frames (ORFs). Unlike other CMS-associat ed ORFs, however, a high level of sequence similarity extends over the enti re length of the nap and pol CMS-associated ORFs. Moreover, in other plant species where more than one form of CMS is found, the nuclear genes that re store fertility to various male sterile cytoplasms represent distinct genes that map to different nuclear loci. The restorers for the nap and pol cyto plasms (Rfn and Rfp, respectively), however, represent different alleles or haplotypes of a single nuclear locus. Both alleles specify factors that in fluence mtRNA processing events, but the specific processing events conditi oned by the two alleles are different, suggesting that the factors encoded by these genes recognize distinct RNA structural features. Finally, unlike other nuclear genes that affect mitochondrial gene expression, Rfn is capab le of modifying the expression of multiple mtDNA regions, some of which are not associated with CMS. Findings made based on this observation are consi stent with the view that new alleles of a restorer locus arise in response to natural selective pressures generated by the appearance of new male ster ile cytoplasms.