Molecular Plant Advance Access originally published online on August 28, 2009
Molecular Plant 2010 3(1):78-90; doi:10.1093/mp/ssp071
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The Formation of Anthocyanic Vacuolar Inclusions in Arabidopsis thaliana and Implications for the Sequestration of Anthocyanin Pigments
a Department of Plant Cellular and Molecular Biology and Plant Biotechnology Center, Ohio State University, Columbus, OH 43210, USA
b Department of Food Science and Technology, The Ohio State University, Columbus, OH 43210, USA
c Present address: Department of Plant Systems Biology, Flanders Institute for Biotechnology, and Department of Plant Biotechnology and Genetics, Ghent University, 9052 Ghent, Belgium
d Current address: Department of Chemistry, Eastern Illinois University, Charleston, IL 61920, USA
1 To whom correspondence should be addressed. E-mail grotewold.1{at}osu.edu, fax (614) 292-5379, tel. (614) 292-2483.
Anthocyanins are flavonoid pigments that accumulate in the large central vacuole of most plants. Inside the vacuole, anthocyanins can be found uniformly distributed or as part of sub-vacuolar pigment bodies, the Anthocyanic Vacuolar Inclusions (AVIs). Using Arabidopsis seedlings grown under anthocyanin-inductive conditions as a model to understand how AVIs are formed, we show here that the accumulation of AVIs strongly correlates with the formation of cyanidin 3-glucoside (C3G) and derivatives. Arabidopsis mutants that fail to glycosylate anthocyanidins at the 5-O position (5gt mutant) accumulate AVIs in almost every epidermal cell of the cotyledons, as compared to wild-type seedlings, where only a small fraction of the cells show AVIs. A similar phenomenon is observed when seedlings are treated with vanadate. Highlighting a role for autophagy in the formation of the AVIs, we show that various mutants that interfere with the autophagic process (atg mutants) display lower numbers of AVIs, in addition to a reduced accumulation of anthocyanins. Interestingly, vanadate increases the numbers of AVIs in the atg mutants, suggesting that several pathways might participate in AVI formation. Taken together, our results suggest novel mechanisms for the formation of sub-vacuolar compartments capable of accumulating anthocyanin pigments.
Key Words: Anthocyanin autophagy cyanidin 3-glucoside vacuolar inclusion vanadate