Not all anthocyanins are born equal: distinct patterns induced by stress in Arabidopsis

Abstract

Different abiotic stress conditions induce distinct sets of anthocyanins, indicating that anthocyanins have different biological functions, or that decoration patterns of each anthocyanin are used for unique purposes during stress. The induction of anthocyanin accumulation in vegetative tissues is often considered to be a response of plants to biotic or abiotic stress conditions. Arabidopsis thaliana (Arabidopsis) accumulates over 20 anthocyanins derived from the anthocyanidin cyanidin in an organ-specific manner during development, but the anthocyanin chemical diversity for their alleged stress protective functions remains unclear. We show here that, when grown in various abiotic stress conditions, Arabidopsis not only often accumulates significantly higher levels of total anthocyanins, but different stress conditions also favor the accumulation of different sets of anthocyanins. For example, the anthocyanin patterns of seedlings grown at pH 3.3 or in media lacking phosphate are very similar and characterized by relatively high levels of the anthocyanins A8 and A11. In contrast, anthocyanin inductive conditions (AIC) provided by high sucrose media are characterized by high accumulation of A9* and A5 relative to other stress conditions. The modifications present in each condition correlate reasonably well with the induction of the respective anthocyanin modification enzymes. Taken together, our results suggest that Arabidopsis anthocyanin profiles provide 'fingerprints' that reflect the stress status of the plants.

Fig. 1

Anthocyanin structure. Common anthocyanidin backbones (a). Arabidopsis anthocyanins analyzed in this study (b). Asterisk indicates a tautomer. See (Pourcel et al. ; Saito et al. ; Tohge et al. 2005) for the complete list of Arabidopsis anthocyanins

Fig. 2

Amount of total anthocyanins produced by Arabidopsis grown in various stress conditions. Plants were cultured under stress conditions, tissues were extracted, and metabolites analyzed as described in the “Materials and methods”. Error bars represent the standard error of the mean (n = 3). ^aLess than control, ^bgreater than control, P < 0.05; two-tailed Student’s t test

Fig. 3

Anthocyanin compositions from Arabidopsis grown in stress conditions. HPLC–PDA chromatograms of aqua-methanol extracts (a–d insets are chromatograms at full scale), percentage of total anthocyanin (e–h labels represent percent composition of total anthocyanin), phenotype (i–l). Conditions; control 0.5MS (a, e, i), pH 3.3 (b, f, j), AIC (c, g, k), 100 mM MgSO₄ (d, h, l). Scale 600 µm

Fig. 4

Clustering of stress responses by anthocyanin metabolite or gene profiles. Hierarchical clustering of stresses by anthocyanin metabolite profiles (a), or by gene expression profiles (b). A schematic representation of the anthocyanin biosynthesis grid in Arabidopsis (c), adapted from (Yonekura-Sakakibara et al. 2012). A5 and A9* metabolites are labeled green, and A8 and A11 red, to emphasize similar induction profiles in Fig. 5. 5GT (At4g14090); A5GlcMalT (At3g29590); A3G2″XylT (At5g54060); A3GlcCouT (At1g03495), SAT (At2g23000); BLGU10 (At4g27830)

Fig. 5

Levels of selected anthocyanins in different stress conditions. A8 (a), A11 (b), A5 (c), A9* (d). Error bars represent standard error of the mean (n = 3). ^aLess than control, ^bgreater than control, P < 0.10; two-tailed Student’s t test