Journal Article

Co-Regulation of Brassinosteroid Biosynthesis-Related Genes During Xylem Cell Differentiation

Ryo Yamamoto, Shozo Fujioka, Kuninori Iwamoto, Taku Demura, Suguru Takatsuto, Shigeo Yoshida and Hiroo Fukuda

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 48, issue 1, pages 74-83
Published in print January 2007 | ISSN: 0032-0781
Published online January 2007 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcl039
Co-Regulation of Brassinosteroid Biosynthesis-Related Genes During Xylem Cell Differentiation

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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To understand the regulatory mechanisms of brassinosteroid (BR) biosynthesis in specific plant developmental processes, we first investigated the accumulation profiles of BRs and sterols in xylem differentiation in a Zinnia culture. The amounts of many substances in the late C28 sterol biosynthetic pathway to campesterol (CR), such as episterol and 24-methylenecholesterol, as well as those in the BR-specific biosynthetic pathway from CR to brassinolide (BL), were elevated in close association with tracheary element differentiation. Among them, 6-deoxotyphasterol (6-deoxoTY) accumulated to unusually high levels within cells cultured in tracheary element-inductive medium, while castasterone (CS) was not elevated either within or outside cells. To identify the molecular basis of this co-up-regulation of BRs and C28 sterols, we isolated Zinnia genes for the key enzymes of BR biosynthesis, ZeSTE1, ZeDIM, ZeDWF4, ZeCPD1 and ZeCPD2. RNA gel blot analysis of these genes indicated a coordinated increase in transcripts for ZeSTE1, ZeDIM, ZeDWF4 and ZeCPD1, and a tracheary element differentiation-specific increase in transcripts for ZeDWF4 and ZeCPD1. In situ hybridization experiments of ZeDWF4 and ZeCPD1 mRNAs revealed their preferential accumulation in procambium cells, immature xylem cells and xylem parenchyma cells. These results suggest that BR biosynthesis during tracheary element differentiation may be regulated by the coordinated regulation of broad sterol biosynthesis and specific regulation of BR biosynthesis, which occurs in part by elevated transcript levels of genes encoding BR biosynthetic enzymes, specifically ZeDWF4 and ZeCPD1. These data provide new insights into the regulation of BR biosynthesis and BR signaling during plant development.

Keywords: Auxin; Brassinosteroid biosynthesis; Cytokinin; Gene expression; Tracheary element differentiation; Zinnia elegans

Journal Article.  5495 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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