Abstract:

The differential expression of 58 open reading frames（ORFs）identified in the intergenic sequence of the mitochondrial genome was analyzed using a male sterile line and a maintainer line of onion（Allium cepa L.），through which，a differentially expressed fragment was obtained，designated as orf393. By quantitative real-time PCR，the temporal-spatial expression of orf393 was carried out in different tissues and organs，including roots，leaves，stalks，and the buds of different developmental stages （pollen mother cells，tetrad，mononuclear，and matured pollen grains）. The results showed that orf393 was only expressed in the samples of the male sterile line；its expression could be detected in all samples of the male sterile line，especially the buds during the tetrad stage，which had the highest expression of orf393. The expression level of orf393 returned to the same level as that during the vegetative stage. Our results suggest that orf393 is constitutively expressed and may associate with the male sterility of onion. Based on the sequence difference of orf393 between the male sterile line and its maintainer line，we developed a reliable molecular marker，namely GXX393，for the identification of cytoplasm types of onion.

Key words: onion, cytoplasmic male-sterility, orf393, gene expression, molecular marker