The expression of pectin methylesterase in onion flower buds is associated with the dominant male-fertility restoration allele

With 6 figures and 2 tablesAbstract In this study, we investigated differential gene expression in the flower buds of male-fertile and male-sterile pools by using the cDNA-sequence-related amplified polymorphism (SRAP) method and discovered a fragment that was specifically expressed in male-fertile pool. Cloning and sequence analysis revealed that this differentially expressed sequence corresponded to a pectin methylesterase gene in Allium cepa (AcPME). This sequence was deposited in GenBank (GU384209). In male-fertility-restored line, AcPME was specifically expressed in tiny buds but not in roots, leaves and bulbs. In male-sterile line and maintainer line, AcPME was not expressed in roots, leaves, bulbs or tiny buds. AcPME was differentially expressed during different flowering stages (I, II, III, IV and V). We developed a PCR-based marker (WHR240) associated with the expression of AcPME. This marker was validated in six other onion lines; in each case, the male-fertility-restored onion was reliably identified. WHR240 therefore permits the efficient marker-assisted selection of maintainer individuals in onion breeding programmes.