Gallagher Larbi J, Betz Stephanie K, Chase Christine D
Horticultural Sciences Department, University of Florida, Gainesville, FL 32611-0690, USA.
Curr Genet. 2002 Dec;42(3):179-84. doi: 10.1007/s00294-002-0344-5. Epub 2002 Nov 28.
Adjacent mitochondrial open reading frames orf355 and orf77 are associated with S cytoplasmic male sterility (CMS-S) in maize, but the mechanisms leading to collapse of developing CMS-S pollen are unknown. Sequence similarity between orf77 and the mitochondrial ATP synthase subunit 9 (atp9) locus led us to examine RNA editing in orf77 and atp9 transcripts of pre-collapse CMS-S microspores. Editing of atp9 was not influenced by the presence of orf77 transcripts. Sequence analysis of cDNA clones demonstrated that atp9 transcripts are fully edited in CMS-S microspores. Orf77 nucleotides corresponding to edited nucleotides in atp9 were either not edited or edited inefficiently within the context of orf77, perhaps due to limited conservation of flanking sequences between orf77 and atp9. However, eight of ten orf77 cDNA clones carried an unexpected terminating edit that truncated orf77 to predict a peptide of 17 amino acids (ORF17) sharing significant identity with the C-terminal transmembrane domain of the ATP9 protein.
相邻的线粒体开放阅读框orf355和orf77与玉米S型细胞质雄性不育（CMS-S）相关，但导致CMS-S花粉发育崩溃的机制尚不清楚。orf77与线粒体ATP合酶亚基9（atp9）基因座之间的序列相似性促使我们研究CMS-S小孢子崩溃前orf77和atp9转录本中的RNA编辑情况。atp9的编辑不受orf77转录本存在的影响。对cDNA克隆的序列分析表明，atp9转录本在CMS-S小孢子中完全被编辑。与atp9中编辑的核苷酸相对应的orf77核苷酸在orf77的背景下要么未被编辑，要么编辑效率低下，这可能是由于orf77和atp9之间侧翼序列的保守性有限。然而，十个orf77 cDNA克隆中有八个发生了意外的终止编辑，该编辑将orf77截短，预测出一个由17个氨基酸组成的肽（ORF17），该肽与ATP9蛋白的C端跨膜结构域具有显著的同源性。
