Tissue-specificity of storage protein genes has evolved with younger gene copies

Y. Wu, J. Messing

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


Seed storage proteins are critical for nitrogen storage in seeds and the nutrition of livestock and humans. In maize synthesis begin 10-12 days after pollination (DAP) and peaks about 18-24 DAP. The major fraction of storage proteins in maize is classified as prolamins, which are rich in the amino acids proline and glutamine. Although storage proteins can accumulate in embryo tissue, the maize prolamins, also called zeins, accumulate in the triploid endosperm. Localization in either embryo or endosperm, however, requires the onset of the synthesis of tissue-specific trans-acting factors in a temporal fashion. It was therefore unexpected that one of the zein genes is strongly expressed in tissue culture. When a chimeric gene controlling expression of the green fluorescence protein (GFP) was introduced into immature cultured embryos by Agrobacterium-mediated transformation, the GFP gave rise to green callus, indicating that the 27-kDa promoter of the gamma zein gene was active. Subsequent analysis of the endogenous 27-kDa gammazein gene showed that 27-kDa gamma-zein protein was made as well, indicating that expression of this gene was not due to the transformation procedure itself. This could be further demonstrated by the fact that the general transacting factor of prolamin genes, the prolamin-box-binding factor (PBF), was also expressed in the green callus. However, the 02 transcription factor that is required for the expression of a subset of alpha zein genes was not expressed, suggesting that tissue-specificity evolved into the combinatorial action of different trans-acting factors along with younger target genes arising from gene duplications.

Original languageEnglish (US)
Pages (from-to)409-415
Number of pages7
Issue number4
StatePublished - 2009

All Science Journal Classification (ASJC) codes

  • Agronomy and Crop Science
  • Genetics
  • Plant Science


  • Developmental gene expression
  • Gamma zein
  • Maize
  • Promoter specificity
  • Storage proteins

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