Expression of a maize storage protein gene in petunia plants is not restricted to seeds

Genes encoding maize seed storage proteins, zeins, are expressed in developing endosperm tissue. To determine whether the DNA sequences controlling the developmental expression of these genes are recognized in dicots, we introduced a gene encoding a M(r) 19,000 zein protein into petunia by Agrobacterium tumefaciens mediated transformation. Southern blot analysis of DNA from regenerated transgenic plants showed that between 1 and 12 copies of the zein gene were integrated at various locations in the petunia genome. S1 nuclease mapping with 5' and 3' probes for zein mRNA showed that transcription of the gene was correctly initiated and terminated in seeds of the transgenic plants. The mRNA was first detected in petunia seeds 10 days after pollination and disappeared 17 days after pollination. However, only small amounts of zein transcripts were synthesized and protein could not be detected at any stage of development. We also found low levels of zein mRNA in leaves, stems, and flowers of the transgenic plants, suggesting that DNA sequences responsible for developmental regulation are not readily recognized in petunia plants.