Abiotic stresses induce different localizations of anthocyanins in Arabidopsis

Abstract

Anthocyanins are induced in plants in response to abiotic stresses such as drought, high salinity, excess light, and cold, where they often correlate with enhanced stress tolerance. Numerous roles have been proposed for anthocyanins induced during abiotic stresses including functioning as ROS scavengers, photoprotectants, and stress signals. We have recently found different profiles of anthocyanins in Arabidopsis (Arabidopsis thaliana) plants exposed to different abiotic stresses, suggesting that not all anthocyanins have the same function. Here, we discuss these findings in the context of other studies and show that anthocyanins induced in Arabidopsis in response to various abiotic stresses have different localizations at the organ and tissue levels. These studies provide a basis to clarify the role of particular anthocyanin species during abiotic stress.

Keywords: A11, cyanidin 3-O-[2-(2-(sinapoyl)xylosyl)-6-O-(4(glucosyl)-p-coumaroyl)glucoside]5-[6-O-(malonyl)glucoside]; A5, cyanidin 3-O-[2-xylosyl-6-O-(4(glucosyl)-p-coumaroyl)]5-[6-O-(malonyl)glucoside]; AIC, anthocyanin induction condition; Arabidopsis; C3G, cyanidin 3-O-glucoside; Col, Columbia-0; HPLC-PDA, extinction coefficient, ϵ; ROS, reactive oxygen species; abiotic stress; anthocyanin; high performance liquid chromatography- photodiode array detection; localization.

Figure 1.

Localization of anthocyanins in Arabidopsis during AIC and MgSO₄ stresses. (A) HPLC-PDA chromatograms of aqua-methanol extracts from whole seedling (Top), cotyledon (second from top), hypocotyl (second from bottom), and root (bottom). Note scale of chromatograms differs. (B) Microscopic analysis of the seedling tissues analyzed in (A). Seedlings grown for 5 days in AIC were lyophilized for 3 days and imaged. Whole seedling prior to dissection (top left), dissected cotyledons (top right), hypocotyls (bottom left), and roots (bottom right). Scale bar 1mm. (C) Detection of anthocyanin pigmentation in cotyledons of seedlings grown in AIC (top), or on 1/2MS 1% sucrose agar medium containing 100 mM MgSO₄ under 150 µmol m² s⁻¹ light (middle) or 40 µmol m² s⁻¹ light (bottom). Mesophyl, m; abaxial epidermis, ab; adaxial epidermis ad; vasculature, v. Scale bar 200 µm. (D) Leaf color of seedling leaf grown for 10 days on 1/2MS 1% sucrose agar medium containing 100 mM MgSO₄ under 150 µmol m² s⁻¹ light (left) or 40 µmol m² s⁻¹ light (right). Note: anthocyanins developed a brown color indicative of oxidation under 150 µmol m² s⁻¹ light. Scale bar 1 mm.