Expression and Interaction Analysis of FAZ1 Protein in Brassica oleracea

Abstract

To identify and characterize genes involved in reproductive tissue abscission in Brassica oleracea, the transcript data of pollinated pistil was analyzed. A differentially expressed gene, named BoFAZ1(FLOWER ABSCISSION ZONE1) was identified, which contains one exon and encompass a 139aa. Furthermore, a T-DNA insertion mutant (SALK_302_G01) (faz1 mutant) was obtained from Arabidopsis thaliana mutant library. Floral organ shedding from mutants was delayed and a V-shaped structure in the boundary region between the stalk and torus of the sepal abscission zone was obtained in faz1 mutant. The cell density of this structure was lower than that of the corresponding region in the wild-type control. In the transgenic plants, the normal development of the stalk zone of faz1 was recovered completely by transforming a 1919-bp DNA fragment of BoFAZ1 into the faz1 mutant. In Addition, our data showed that BoFAZ1 was expressed in mature pollen grains, but not in the bracts, roots, stems, leaves, and sepals. Its expression in the filaments, stigma, and pistil exfoliation layer gradually increased after pollination. Subcellular localization experiments showed that BoFAZ1 was located in the cell membrane. A myristoylation site was found at the N-terminus of BoFAZ1. Removal of this site resulted in protein dislocation in the cytoplasm, cell membrane and nucleus. Finally, a yeast two-hybrid test indicated that BoH3.2 (histone H3.2), a protein involved in abscission zone development, interacted with BoFAZ1. This interaction was verified by a GST pull-down assay. In summary, our data indicated that BoFAZ1 was involved in the formation of the pistil abscission zone in B. oleracea.