Functional analysis of female gametophyte specific promoters in Chinese cabbage

• Isolation of female gametophyte specific promoters At5g40260 and BRA0029160.
• At5g40260 promoter was more efficient than BRA0029160.
• The sequence homology between At5g40260 and BRA0029160 was 73% and promoter was 62%.
• In the development stage of ovule, GUS was expressed in the embryo sac.
• After bud pollination, GUS was detected in inner integument of embryo sac.

Female gametophyte, also called embryo sacs, plays an important role during double fertilization in angiosperm. The objective of this study was to develop specific promoters for female gametophyte to induce new fertility systems and protect varieties. Upstream region of At5g40260 gene, characterized female gametophyte specific expression gene in Arabidopsis, and upstream region of BRA0029160 gene in Chinese cabbage, homologous gene of At5g40260, were investigated to develop female gametophyte specific promoters. GUS reporter genes, which was driven by these two upstream regions of the gene (promoters), were detected in embryo sac and central vacuole. However, promoter of At5g40260 gene drove stronger expression than promoter of BRA0029160 gene in transgenic Chinese cabbage. Histochemical analysis revealed promoter of At5g40260 gene drove GUS expression in inner integument of division tissue of embryo sac in T1 generation. Enzyme activity assay showed GUS gene expression in the embryo. Analysis of At5g40260 and BRA0029160 promoters by PlantCARE database revealed many cis-elements regulated initiation and modulation of the gene expression.