Journal Article

Identification of a <i>cis</i>-Regulatory Element that Acts in Companion Cell-Specific Expression of <i>AtMT2B</i> Promoter through the use of <i>Brassica</i> Vasculature and Gene-Gun-Mediated Transient Assay

Ryo Tsuwamoto and Takeo Harada

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 51, issue 1, pages 80-90
Published in print January 2010 | ISSN: 0032-0781
Published online November 2009 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcp169
Identification of a cis-Regulatory Element that Acts in Companion Cell-Specific Expression of AtMT2B Promoter through the use of Brassica Vasculature and Gene-Gun-Mediated Transient Assay

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  • Biochemistry
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  • Plant Sciences and Forestry

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The molecular basis underlying the development, maintenance and function of companion cells in plants is largely unknown. The identification of several genes expressed specifically in companion cells implies the contribution of specific transcriptional elements to the identity of companion cells. However, less is known about the companion cell-specific transcriptional regulation of promoters. We established a novel assay method using gene-gun delivery of partially deleted promoters to string-containing vascular bundles excised from the petiole of Brassica napus for the rapid identification of cis-elements. To test this system, we analyzed the Arabidopsis METALLOTHIONEIN 2B (MT2B) gene, which is expressed in companion cells. The assay revealed a 49-bp region possessing two predicted cis-regulatory elements: a G-box and an evening element-related sequence (EEr), and EEr showed higher activity. We confirmed the reliability of the result with stable transformants harboring a deleted MT2B promoter:GUS transgene. The lack of EEr completely eliminated the MT2B-like expression, but the lack of G-box did not eliminate it. We conclude that EEr is a major cis-regulatory element of the MT2B promoter. Our method will help to explain the transcriptional background of companion cells through the rapid identification of cis-regulatory regions.

Keywords: Brassica napus; cis-element; Companion cell; Gene-gun; Promoter analysis; Vasculature

Journal Article.  5628 words.  Illustrated.

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

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