The GCN4 motif in a rice glutelin gene is essential for endosperm‐specific gene expression and is activated by Opaque‐2 in transgenic rice plants
1998; Wiley; Volume: 14; Issue: 6 Linguagem: Inglês
10.1046/j.1365-313x.1998.00167.x
ISSN1365-313X
AutoresChuanyin Wu, Akihiro Suzuki, H Washida, Fumio Takaiwa,
Tópico(s)Plant Reproductive Biology
ResumoSummary The GCN4 motif is conserved in a number of seed storage protein genes, and promoter fragments containing this motif have been shown to be involved in controlling seed‐specific expression of the genes studied. All genes encoding the rice seed storage protein glutelin contain the GCN4 motif at similar sites in their 5′ flanking regions. Using a stable homologous transgenic system, we have analysed the promoter of the rice glutelin gene GluB‐1 and demonstrated that the GCN4 motif functions as an essential cis ‐element for endosperm‐specific gene expression. Moreover, a 21 bp GluB‐1 promoter fragment spanning the GCN4 motif, as a multimer, directed GUS gene expression in endosperm of transgenic rice plants, when fused directly to the core promoter (–46) of CaMV 35S. In transiently transfected rice protoplasts, over a hundred‐fold transactivation was observed from the 21 bp sequence by the bZIP type transcriptional activator Opaque‐2 (O2) co‐expressed under a CaMV 35S promoter. The transactivation was also evident in transgenic plants containing both O2 and the 21 bp sequence/ GUS fusion. The O2‐mediated activation requires binding of O2 to an intact GCN4 motif. Our results suggest that a bZIP protein functionally similar to O2 may exist in rice and participate in controlling the endosperm‐specific expression of GluB‐1 through the GCN4 motif.
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