Journal Article

Functional analysis of a RING domain ankyrin repeat protein that is highly expressed during flower senescence

Xinjia Xu, Cai-Zhong Jiang, Linda Donnelly and Michael S. Reid

in Journal of Experimental Botany

Published on behalf of Society for Experimental Biology

Volume 58, issue 13, pages 3623-3630
Published in print October 2007 | ISSN: 0022-0957
Published online October 2007 | e-ISSN: 1460-2431 | DOI: http://dx.doi.org/10.1093/jxb/erm212

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A gene encoding a RING zinc finger ankyrin repeat protein (MjXB3), a putative E3 ubiquitin ligase, is highly expressed in petals of senescing four o'clock (Mirabilis jalapa) flowers, increasing >40 000-fold during the onset of visible senescence. The gene has homologues in many other species, and the Petunia homologue is strongly up-regulated in senescing Petunia corollas. Silencing the expression of this gene in Petunia, using virus-induced gene silencing, resulted in a 2 d extension in flower life. In Mirabilis, a 2 kb promoter region, 5’ upstream of the MjXB3 gene, was isolated. The promoter sequence included putative binding sites for many DNA-binding proteins, including the bZIP, Myb, homeodomain-leucine zipper (HD-Zip), MADS-box, and WRKY transcription factors. The construct containing a 1 kb promoter region immediately upstream of the MjXB3 gene drove the strongest expression of the β-glucuronidase (GUS) reporter gene in a transient expression assay. In Petunia, GUS expression under the control of this heterologous promoter fragment was specific to senescing flowers. The Mirabilis promoter GUS construct was tested in other flower species; while GUS activity in carnation petals was high during senescence, no expression was detected in three monocotyledonous flowers—daylily (Hemerocallis ‘Stella d'Oro’), daffodil (Narcissus pseudonarcissus ‘King Alfred’), and orchid (Dendrobium ‘Emma White’).

Keywords: Floral senescence; Mirabilis jalapa; senescence-associated genes; transcription factor; ubiquitin ligase

Journal Article.  3753 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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