Abstract
Anthocyanins are water-soluble polyphenolic compounds with a high nutraceutical value. Despite the fact that cultivated tomato varieties do not accumulate anthocyanins in the fruit, the biosynthetic pathway can be activated in the vegetative organs by several environmental stimuli. Little is known about the molecular mechanisms regulating anthocyanin synthesis in tomato. Here, we carried out a molecular and functional characterization of two genes, SlAN2 and SlANT1, encoding two R2R3-MYB transcription factors. We show that both can induce ectopic anthocyanin synthesis in transgenic tomato lines, including the fruit. However, only SlAN2 acts as a positive regulator of anthocyanin synthesis in vegetative tissues under high light or low temperature conditions.
Highlights
In plants, anthocyanins accumulate as water-soluble polyphenolic metabolites in the vacuole of manyepidermal cell types, where they exert different functions depending on the tissue specificity
Four different tomato MYB proteins, encoded by the genes Solyc10g086250, Solyc10g086260, Solyc10g086270, and Solyc10g086290, corresponding, respectively, to S. lycopersicum Anthocyanin2 (SlAN2) [33,34,35], S. lycopersicum Anthocyanin1 (SlANT1) [32,36], SlANT1like [35,54] and SlAN2like [35], grouped in one clade with MYB proteins of tobacco (N. tabacum), petunia and potato (S. tuberosum) involved in anthocyanin synthesis [5,55,56] (S1 Fig, Fig 1A). This clade included members from the Solanaceae family and was clearly separated from anthocyanin MYBs from other dicots, such as A. thaliana or A. majus, and monocots (S1 Fig, Fig 1A). This analysis confirms that SlANT1 and SlAN2 are tomato MYB transcription factors (TFs) involved in anthocyanin synthesis regulation
To identify possible tomato regulators belonging to the basic helix-loop-helix (bHLH) and WDR families to be included in our analyses, a similar phylogenetic approach was followed
Summary
Anthocyanins accumulate as water-soluble polyphenolic metabolites in the vacuole of many (sub)epidermal cell types, where they exert different functions depending on the tissue specificity. In vegetative tissues anthocyanins act as protective compounds after being synthesized in response to different environmental stimuli (e.g. UV irradiation and/or low temperature) and against pathogens, while in reproductive organs they exert an essential role in attracting pollinators and seed dispersers to assure the reproductive success [1]. A role for anthocyanins as reducing agents and signaling molecules involved in the modulation of ROS-signaling pathways emerged [2]. Given their physiological importance, the production of anthocyanins must be tightly regulated in plant cells and the regulatory network controlling their biosynthesis has been extensively studied in different species. In petunia (Petunia x hybrida) flowers, for example, different members of the PLOS ONE | DOI:10.1371/journal.pone.0136365 August 26, 2015
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