Functional Characterization of TaFUSCA3, a B3-Superfamily Transcription Factor Gene in the Wheat.

The end-use quality of wheat, including its unique rheology and viscoelastic properties, is predominantly determined by the composition and concentration of gluten proteins. While, the mechanism regulating expression of the seed storage protein (SSP) genes and other related genes in wheat remains unclear. In this study, we report on the cloning and functional identification of , a B3-superfamily transcription factor (TF) gene in wheat. Sequence alignment indicated that wheat and barley genes are highly conserved. Quantitative reverse-transcription (qRT)-PCR analysis showed that the transcript of was accumulated mostly in the stamens and the endosperms of immature wheat seeds. Yeast-one-hybrid results proved that the full-length TaFUSCA3 and its C-terminal region had transcriptional activities. Yeast-two-hybrid and bimolecular fluorescence complementation assays indicated that TaFUSCA3 could activate the expression of the high molecular weight glutenin subunit gene and interact with the seed-specific bZIP protein TaSPA. DNA-protein-interaction enzyme-linked immunosorbent assay demonstrated that TaFUSCA3 specifically recognizes the RY-box of the promoter region. Transient expression results showed that TaFUSCA3 could -activate the promoter, which contains eight RY-box sequences. TaFUSCA3 was unable to activate the downstream transcription when the RY-box was fully mutated. TaFUSCA3 could activate the transcription of the gene promoter in a complementation of loss-of-function experiment using the line , which is a mutant, demonstrating the evolutionary conservation of the gene. In conclusion, the wheat B3-type TF, TaFUSCA3, is functional conserved between monocot and dicot, and could regulate SSP gene expression by interacting specifically with TaSPA.