Characterization and functional analysis of a novel PCP gene BcMF5 from Chinese cabbage (Brassica campestris L. ssp. chinensis Makino)

Brassica campestris Male Fertile 5 (BcMF5), a novel member of the pollen coat protein class A (PCP-A) gene family, was identified from Brassica campestris L. ssp. chinensis Makino (Chinese cabbage-pak-choi). Temporal and spatial expression analysis showed that BcMF5 is a late-expressed PCP gene related to the process of determining pollen fertility. Functional analysis by hairpin RNA (hpRNA)-mediated RNA interference also showed that the expression of BcMF5 is inhibited, which resulted in the low germination ability of the pollen and also in an abnormality of the pollen exemplified by a collapsed germination furrow. This demonstrates that the expression of BcMF5 is closely related to the tapetum. Further, the expression profile of the BcMF5 promoter in Arabidopsis was also analyzed. This analysis indicated that the BcMF5 promoter began expression in the early stage of anther development and drove high levels of glucuronidase (GUS) expression in anthers, pollen, and the pollen tube in the late stage of pollen development, but did not drive any expression in petals, sepals, or pistils. Together with the functional analysis, the hypothesis that BcMF5 may have a sporophytic or gametophytic expression pattern is presented.