Abstract: In an effort to study the molecular mechanism of genic male sterility in plants, BcMF3 gene
that encodes a pectin methylesterase ( PME) was isolated from the fertile B line of Chinese cabbage-pak-choi
(Brassica campestris ssp. chinensis var. communis, syn. B. rapa ssp. chinensis var. communis) previously.
In the present paper, primerswere designed based on the cDNA sequence of B cM F3, and a 458 bp fragment
and a 538 bp fragmentwere amp lified from the cDNA of flower buds of Chinese cabbage-pak-choi. These two
fragmentswere introduced into binary vector pB I121 in antisense orientation and sense orientation respectively,
and the generated RNA interference (RNAi) vector was then mobilized into Agrobacterium tum efaciens strain
LBA4404. The A. tum efaciens harboring the BcMF3 fragment was transformed to flowering Chinese cabbage
(B. campestris ssp. chinensis var. parachinensis) via tissue culture. The pollen grains from app roximately
50% of RNAi plants exhibited abnormal shapes, and only 32.3% of pollens from RNAi plants germinated nor
mally. The PME activity of the anther from RNAi plants with abnormal pollens decreased by 13.5%. These
results showed that functional interruption of BcMF3 by RNAi resulted in pollen abortion in flowering Chinese
cabbage, which p robably caused by the decrease of PME activity. The study suggests that the product of
BcMF3 gene plays an important role during pollen development in Cruciferae crop s such as flowering Chinese
cabbage and Chinese cabbage-pak-choi.

Key words: Chinese cabbage-pak-choi, Brassica campestris, Flowering Chinese cabbage, Pollen