Activation of ADP-Glucose Pyrophosphorylase Gene Promoters by a WRKY Transcription Factor, AtWRKY20,<i>in Arabidopsis thaliana</i>L. and Sweet Potato (<i>Ipomoea batatas</i>Lam.)

  • Nagata Takafumi
    Graduate School of Bioresource and Bioenviromental Science, Kyushu University, Japan
  • Hara Hiromichi
    Graduate School of Bioresource and Bioenviromental Science, Kyushu University, Japan
  • Saitou Kazuyuki
    Faculty of Agriculture (Graduate School), Kyushu University, Japan
  • Kobashi Akiko
    Graduate School of Bioresource and Bioenviromental Science, Kyushu University, Japan
  • Kojima Kengo
    Graduate School of Bioresource and Bioenviromental Science, Kyushu University, Japan
  • Yuasa Takashi
    Faculty of Agriculture (Graduate School), Kyushu University, Japan
  • Ueno Osamu
    Faculty of Agriculture (Graduate School), Kyushu University, Japan

書誌事項

タイトル別名
  • Activation of ADP-Glucose Pyrophosphorylase Gene Promoters by a WRKY Transcription Factor, AtWRKY20, in Arabidopsis thaliana L. and Sweet Potato (Ipomoea batatas Lam.)

抄録

ADP–glucose pyrophosphorylase (AGPase) catalyzes the first limiting step in starch biosynthesis in plants. However, the direct transcriptional activator of the AGPase genes has not yet been determined. We have isolated a WRKY transcription factor cDNA, AtWRKY20, from Arabidopsis thaliana and purified the corresponding protein. Transient expression of AtWRKY20 by particle bombardment enhanced expression of the promoter of ApL3, encoding a sugar-inducible AGPase large subunit gene of A. thaliana, in leaves of A. thaliana. AtWRKY20 bound to the ApL3 promoter in vitro. The expression of AtWRKY20 was strongly induced by sucrose or, to a lesser extent, by mannitol, and the expression pattern of the ApL3 gene mimicked that of the AtWRKY20 gene. Transient expression experiments demonstrated that AtWRKY20 also activated the promoter of Koganesengan ibAGP1 encoding an AGPase small subunit gene of sweet potato var. Koganesengan. A 5’–end deletion analysis revealed a negative regulatory region from –1371 to –641 and a positive regulatory region from –640 to –180 in the Koganesengan ibAGP1 promoter. AtWRKY20 interacted directly with the region between positions –623 and –490 in the Koganesengan ibAGP1 promoter. These results suggest that AtWRKY20 functions directly as a transcriptional activator of the ApL3 promoter and regulates the expression of ApL3 induced by sucrose or osmoticum in A. thaliana. Moreover, AtWRKY20 can enhance the expression of the Koganesengan ibAGP1 promoter directly in sweet potato.

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