Compartmentalized expression of two structurally and functionally distinct 4-coumarate:CoA ligase genes in aspen ( <i>Populus tremuloides</i> )

DOI Web Site 被引用文献16件
  • Wen-Jing Hu
    Plant Biotechnology Research Center, School of Forestry and Wood Products, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931
  • Akiyoshi Kawaoka
    Plant Biotechnology Research Center, School of Forestry and Wood Products, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931
  • Chung-Jui Tsai
    Plant Biotechnology Research Center, School of Forestry and Wood Products, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931
  • Jrhau Lung
    Plant Biotechnology Research Center, School of Forestry and Wood Products, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931
  • Keishi Osakabe
    Plant Biotechnology Research Center, School of Forestry and Wood Products, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931
  • Hiroyasu Ebinuma
  • Vincent L. Chiang
    Plant Biotechnology Research Center, School of Forestry and Wood Products, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931

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<jats:p> 4-Coumarate:CoA ligases (4CLs, EC <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="ec" xlink:href="6.2.1.12">6.2.1.12</jats:ext-link> ) are a group of enzymes necessary for maintaining a continuous metabolic flux for the biosynthesis of plant phenylpropanoids, such as lignin and flavonoids, that are essential to the survival of plants. So far, various biochemical and molecular studies of plant 4CLs seem to suggest that 4CL isoforms in plants are functionally indistinguishable in mediating the biosynthesis of these phenolics. However, we have discovered two functionally and structurally distinct 4CL genes, <jats:italic>Pt4CL1</jats:italic> and <jats:italic>Pt4CL2</jats:italic> (63% protein sequence identity), that are differentially expressed in aspen ( <jats:italic>Populus tremuloides</jats:italic> ). The <jats:italic>Escherichia coli</jats:italic> -expressed and purified Pt4CL1 and Pt4CL2 proteins exhibited highly divergent substrate preference as well as specificity that reveal the association of Pt4CL1 with the biosynthesis of guaiacyl–syringyl lignin and the involvement of Pt4CL2 with other phenylpropanoid formation. Northern hybridization analysis demonstrated that <jats:italic>Pt4CL1</jats:italic> mRNA is specifically expressed in lignifying xylem tissues and <jats:italic>Pt4CL2</jats:italic> mRNA is specifically expressed in epidermal layers in the stem and the leaf, consistent with the promoter activities of <jats:italic>Pt4CL1</jats:italic> and <jats:italic>Pt4CL2</jats:italic> genes based on the heterologous promoter-β-glucouronidase fusion analysis. Thus, the expression of <jats:italic>Pt4CL1</jats:italic> and <jats:italic>Pt4CL2</jats:italic> genes is compartmentalized to regulate the differential formation of phenylpropanoids that confer different physiological functions in aspen; <jats:italic>Pt4CL1</jats:italic> is devoted to lignin biosynthesis in developing xylem tissues, whereas <jats:italic>Pt4CL2</jats:italic> is involved in the biosynthesis of other phenolics, such as flavonoids, in epidermal cells. </jats:p>

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