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

为了研究甜菜细胞质雄性不育（CMS）的分子基础，我们对含有可育细胞质和雄性不育细胞质的两个甜菜品系的线粒体基因组进行了详细的比较。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。在雄性可育、CMS和核恢复的甜菜基因型中，比较了已知线粒体基因的转录本和两个已知相对重排的甜菜基因组区域。在大多数情况下，对所有三种mtrna（从叶子或花蕾制备）观察到相同的转录模式，表明重排事件没有发生在转录单位内。然而，六个基因，coxI,coxII,atpA,rps3， orf324和orf1的转录模式发生了改变。有趣的是，coxI转录本受到核背景的显著影响，而背景不清楚对其他五个基因的转录本没有影响。结果表明，核恢复基因对coxI转录模式有影响，并与coxI在甜菜雄性不育中的表达有关。

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.