A polygalacturonase inhibitory protein gene (BcMF19) expressed during pollen development in Chinese cabbage-pak-choi

The level of polygalacturonase inhibitory protein (PGIP) genes involved in pollen development remains unclear. Characterization of the different PGIP genes that are expressed in pollen is necessary in understanding the similarities and differences of functions between the members of this gene family, as well as the underlying mechanism of pollen development. A gene-encoding putative PGIP, BcMF19 was successfully cloned on a cDNA-amplified fragment length polymorphism fragment after it was found to be up-regulated in the fertile flower buds of Chinese cabbage-pak-choi (Brassica campestris L. ssp. chinensis Makino) genic male sterile AB line (Bajh97-01A/B). The amino acid sequence of BcMF19 possessed the basic feature of PGIPs, containing an N-terminal signal peptide, several potential N-glycosylation sites, two disulfide bridges flanking both the N- and C-terminal regions, and 10 leucine-rich repeat (LRR) consensus sequences. Real-time RT-PCR verified the higher expression of BcMF19 in the fertile flower buds compared to the sterile flower buds. In situ hybridization showed that BcMF19 was exclusively expressed in the tapetal cells and microspores during anther development. These results indicate that BcMF19 is a novel PGIP gene that might be involved in pollen or tapetum development.