Molecular Mechanism of Cytoplasmic Male Sterility in Sugarbeet (Beta vulgaris L.)

为了研究甜菜细胞质雄性不育的分子基础，我们对甜菜两个品系的线粒体基因组进行了详细的比较，其中一个品系含有可育(N)细胞质，另一个品系含有雄性不育细胞质。这两个基因组有大约330kb的共同序列，但在序列组织上有相当大的差异，这可以通过基因组重排来解释。将已知的线粒体基因的转录本和两个甜菜基因组的已知重排区域在雄性可育、CMS和核恢复甜菜基因型之间进行了比较。在大多数情况下，观察到所有三个mtRNAs(从叶或花蕾制备)的转录模式相同，表明在转录单位内没有发生重排事件。但发现Coxi、CoxII、atpa、rps 3、orf324和orf1等6个基因的转录本发生了变化。有趣的是，Coxi的转录本受到核背景的显著影响，而背景不清对其他5个基因的转录本没有影响。结果表明，核恢复基因S对Coxi的转录谱有影响，并与Coxi有关。

To study the molecular basis of cytoplasmic male sterility (CMS) in sugarbeet, we have conducted a detailed comparison of the mitochondrial genomes of two sugarbeet lines, one containing a fertile (N) cytoplasm and the other a male sterile one. The two genomes have approximately 330kb of common sequences but there is considerable variation in sequence organization which can be accounted for by genome rearrangements.Transcripts for known mitochondrial genes and regions of the two sugarbeet genomes known to be rearranged relative to one another were compared among male-fertile, CMS and nuclear-restored sugarbeet genotypes. In most instances, identical transcript patterns were observed for all three, mtRNAs (prepared from leaves or flower buds), indicating that rearrangement events did not occur within transcriptional units. Altered transcript patterns were, however, identified for six genes, coxI,coxII,atpA,rps3, orf324, and orf1.Interestingly, the coxI transcripts were found to be significantly affected by nuclear background, whereas unclear background has no effect on the transcripts of other five genes.The results suggest that nuclear-restorer gene (s) have an effect on coxI transcript patterns and implicate coxI in sugarbeet male sterility.