Journal Article

Regulation of HSD1 in Seeds of <i>Arabidopsis thaliana</i>

Sébastien Baud, Neel Reinhard Dichow, Zsolt Kelemen, Sabine d’Andréa, Alexandra To, Nathalie Berger, Michel Canonge, Jocelyne Kronenberger, David Viterbo, Bertrand Dubreucq, Loïc Lepiniec, Thierry Chardot and Martine Miquel

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 50, issue 8, pages 1463-1478
Published in print August 2009 | ISSN: 0032-0781
Published online June 2009 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcp092
Regulation of HSD1 in Seeds of Arabidopsis thaliana

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The hydroxysteroid dehydrogenase HSD1, identified in the proteome of oil bodies from mature Arabidopsis seeds, is encoded by At5g50600 and At5g50700, two gene copies anchored on a duplicated region of chromosome 5. Using a real-time quantitative reverse transcriptase–polymerase chain reaction (RT–PCR) approach, the accumulation of HSD1 mRNA was shown to be specifically and highly induced in oil-accumulating tissues of maturing seeds. HSD1 mRNA disappeared during germination. The activity of HSD1 promoter and the localization of HSD1 transcripts by in situ hybridization were consistent with this pattern. A complementary set of molecular and genetic analyses showed that HSD1 is a target of LEAFY COTYLEDON2, a transcriptional regulator able to bind the promoter of HSD1. Immunoblot analyses and immunolocalization experiments using anti-AtHSD1 antibodies established that the pattern of HSD1 deposition faithfully reflected mRNA accumulation. At the subcellular level, the study of HSD1:GFP fusion proteins showed the targeting of HSD1 to the surface of oil bodies. Transgenic lines overexpressing HSD1 were then obtained to test the importance of proper transcriptional regulation of HSD1 in seeds. Whereas no impact on oil accumulation could be detected, transgenic seeds exhibited lower cold and light requirements to break dormancy, germinate and mobilize storage lipids. Interestingly, overexpressors of HSD1 over-accumulated HSD1 protein in seeds but not in vegetative organs, suggesting that post-transcriptional regulations exist that prevent HSD1 accumulation in tissues deprived of oil bodies.

Keywords: Arabidopsis thaliana; hydroxysteroid dehydrogenase 1; LEAFY COTYLEDON2; oil bodies; seed; triacylglycerol

Journal Article.  9828 words.  Illustrated.

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

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