Zein promoter function in carrot and maize protoplasts
Abstract
Zeins are a group of alcohol-soluble proteins that are synthesized in the endosperm of developing maize seeds. These proteins are encoded by a large number of genes located on several chromosomes; based upon the number of mutants that have been isolated, zein gene regulation is complex. Comparisons of gene flanking regions reveal conserved sequences that may be important for their regulation. Studies of transformed plant tissues support the assertion that cis-acting elements within the 5$\sp\prime$ flanking regions of zein genes are required for accurate transcription. The purpose of this investigation was to determine the role(s) of conserved sequences in the 5$\sp\prime$ flanking region of an $\alpha$-zein gene, and to assess the interactions between the potential regulatory sequences. Upstream DNA sequences and promoter deletions from the 5$\sp\prime$ flanking region of an $\alpha$-zein gene were fused to the GUS reporter-gene and analyzed for transient GUS expression in carrot and somatic maize protoplasts. In carrot protoplasts, a 121 bp DNA sequence that has the conserved $-$300 element activated transcription when placed in either orientation relative to the zein promoter and activated low levels of transcription from the inverted zein promoter. The $-$300 element was deleted and was not an essential part of the activating sequence. Adjacent sequences 5$\sp\prime$ of the 121 bp sequence did not function independently but further activated transcription from the zein promoter in combination with the 121 bp sequence. The upstream activating sequences also function independently of the CAAT region. However, the CAAT region is required for maximum promoter function. Zein promoter-GUS constructs did not function in somatic maize protoplasts. Also, the CaMV 35S enhancer did not activate transcription from zein promoters in maize protoplasts. A specific interaction between factors binding to zein upstream and downstream elements may be required for zein gene transcription in maize endosperm.
Degree
Ph.D.
Advisors
Larkins, Purdue University.
Subject Area
Molecular biology
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