Abstract: In various embodiments, the invention provides expression systems for heterologous protein expression in vegetative plant tissues, utilizing plant seed gene components that are adapted to orchestrate high levels of vegetative protein production. The expression systems may include host plant cells having recombinant genomes, and the plant cells may be maintained under protein expressing conditions, for example in tissue culture. The cells may be induced to express an ABI3 transcription factor, for example by transformation with a vector having a constitutive ABI3 expression cassette. The recombinant sequences in operative linkage may include an integrated expression promoter responsive to the ABI3 transcription factor, such as an arcelin gene promoter, a vicilin gene promoter and a napin gene promoter. A 5? untranslated region may include a region of an ABA responsive plant seed gene or an ABI3 responsive plant seed gene. A plant secretion signal peptide coding sequence may be included.

Abstract: In various embodiments, the invention provides expression systems for heterologous protein expression in vegetative plant tissues, utilizing plant seed gene components that are adapted to orchestrate high levels of vegetative protein production. The expression systems may include host plant cells having recombinant genomes, and the plant cells may be maintained under protein expressing conditions, for example in tissue culture. The cells may be induced to express an ABD transcription factor, for example by transformation with a vector having a constitutive ABB expression cassette. The recombinant sequences in operative linkage may include an integrated expression promoter responsive to the ABI3 transcription factor, such as an arcelin gene promoter, a vicilin gene promoter and a napin gene promoter. A 5? untranslated region may include a region of an ABA responsive plant seed gene or an AB 13 responsive plant seed gene. A plant secretion signal peptide coding sequence may be included.

Abstract: A nucleotide sequence is provided for expression of a heterologous protein of interest that is localized to the endoplasmic reticulum protein bodies in transgenic plants, plant cells, and seeds. Said nucleotide sequence comprises a promoter, the 5? untranslated region from the maize ?-zein gene, the ?-zein signal peptide sequence, a sequence encoding a heterologous protein of interest, and the 3? untranslated region from the maize ?-zein gene, operatively linked.