The invention is directed to synthetic promoter constructs for enhanced transgene expression in plants and to expression cassettes comprising the synthetic promoter constructs. The expression cassettes may include various elements for improved expression, stability of the expressed protein or efficient purification of the expressed protein, including signal sequences, protease cleavage sites for release of the target protein, trafficking peptides for trafficking of the expressed protein to various plant compartments, and/or various tags. The invention further relates to methods of expression of transgenic proteins in plants with the use of the synthetic promoter constructs and expression cassettes.