Transcript profiling of a dominant male sterile mutant (Ms-cd1) in cabbage during flower bud development

A spontaneous male-sterile mutation affecting anther development has been identified in cabbage line 79-399-3. The male sterility was associated with abnormal callose degeneration and failure of microspore separation during anther development. Three pairs near-isogenic lines (NILs) with or without the dominant male sterility allele (MS-cd1) were profiled by cDNA-AFLP to detect differentially expressed genes during flower bud development. Out of 6500 transcript derived fragments (TDFs) inspected, 27 were differentially expressed between fertile and male sterile plants in all three sets of NILs. All 27 TDFs were sequenced and BLAST searching revealed that 14 out of 27 fragments were highly homologous to genes with known or predicted function in Arabidopsis. Moreover, three of these TDFs were homologous to genes involved in cell wall formation and degradation, including plant invertase/pectin methylesterase inhibitor (PMEI) and polysaccharide lyase. RT-PCR experiments revealed that PMEI was expressed strongly in the anther and filament. Analysis of a set of NILs with different male sterility types showed that PMEI was also not expressed in a Nigra CMS NIL, a recessive male sterile NIL and an Ogura CMS NIL compared to their corresponding fertile NILs. Based on both cytological and transcriptional data we suggest that the dominant MS-cd1 mutant gene may disrupts proper separation of pollens from tetrads, which leads to the suppressed expression of a number of genes including BoPMEI1, a gene likely involved in the degradation of pectin