Epidermal coumaroyl anthocyanins protect sweet basil against excess light stress: multiple consequences of light attenuation

Abstract

The putative photoprotective role of foliar anthocyanins continues to attract heated debate. Strikingly different experimental set-ups coupled with a poor knowledge of anthocyanin identity have likely contributed to such disparate opinions. Here, the photosynthetic responses to 30 or 100% solar irradiance were compared in two cultivars of basil, the green-leafed Tigullio (TG) and the purple-leafed Red Rubin (RR). Coumaroyl anthocyanins in RR leaf epidermis significantly mitigated the effects of high light stress. In full sunlight, RR leaves displayed several shade-plant traits; they transferred less energy than did TG to photosystem II (PSII), and non-photochemical quenching was lower. The higher xanthophyll cycle activity in TG was insufficient to prevent inactivation of PSII in full sunlight. However, TG was the more efficient in the shade; RR was far less able to accommodate a large change in irradiance. Investment of carbon to phenylpropanoid biosynthesis was more in RR than in TG in the shade, and was either greatly enhanced in TG or varied little in RR because of high sunlight. The metabolic cost of photoprotection was lower whereas light-induced increase in biomass production was higher in RR than in TG, thus making purple basil the more light tolerant. Purple basil appears indeed to display the conservative resource-use strategy usually observed in highly stress tolerant species. We conclude that the presence of epidermal coumaroyl anthocyanins confers protective benefits under high light, but it is associated with a reduced plasticity to accommodate changing light fluxes as compared with green leaves.

Photoperiod and shading regulate coloration and anthocyanin accumulation in the leaves of malus crabapples

“…Anthocyanin accumulation and coloration of fruits are affected by many cultivation practices, such as the use of reflective mulches or bagging, that may change the light environment within the tree canopy and around individual fruits (Ju et al 1999;Huang et al 2009;Overbeck et al 2013). The contents of flavonoids such as anthocyanin, catechins and flavonols increased in the leaves of Phillyrea latifolia and sweet potato during leaf exposure to sunlight or a long-day photoperiod (Carvalho et al 2010;Tattini et al 2014). We did not observe a red color in the leaves or calli under short-day conditions or in darkness.…”

Can Anthocyanins be Part of the Metal Homeostasis Network in Plant?

“…Firstly, because anthocyanins originated from hydroxycinnamic acids and, as all the other flavonoids, they have evolved in more complexes chemical structures. Secondly, in addition to the protection against UV, especially due to acylation with phenolic acids (i.e., coumaric acid; Tattini et al, 2014), they serve as visible light filter as well as powerful antioxidants (Gould et al, 2009;Landi et al, 2015). Thus, anthocyanins exhibit properties of other different classes of molecules, but enclosed in a single one confirming the second criterion of the evolution: the efficiency of energy utilization.…”

“…While there are six common anthocyanidins, there are more than 600 anthocyanins isolated from plants , 277 of which have been identified after 1992 (Andersen and Jordheim, 2006). In view of the chemical structure of anthocyanins and their histological localization, different protective functions have been hypothesized even though, concerning plant protection against abiotic stress, photoprotection from high light and UV-B (Agati et al, 2007;Tattini et al, 2014) and ROS scavenging ability are the most widely postulated as stress reliever (Gould et al, 2002;Kytridis and Manetas, 2006). On the other hand, defence against herbivores and attraction of pollinators (or preys in carnivorous plants) are the most proposed functions for anthocyanins in terms of relationships with biotic factors (Gould et al, 2009;Hughes and Lev-Yadun, 2015;Menzies et al, 2015).…”

Multiple functional roles of anthocyanins in plant-environment interactions

“…Because acylated anthocyanins are not as common as the non-acylated forms, their UV-absorbing functions are unlikely to be a universal primary role for anthocyanins in planta (Hatier and Gould, 2009). However, only a few studies on photo-abatement have fully identified the chemical structure of individual anthocyanins inside the leaf (Burger and Edwards, 1996;Andersen et al, 2010;Tattini et al, 2014), and acylated anthocyanins may be more abundant in leaves than has been previously assumed. It is perhaps surprising that in most studies anthocyanins are quantified only spectrophotometrically by measuring the absorbance of the total pool.…”

“…The common anthocyanin glycosides have negligible molar absorption coefficients in the UV region (Woodall and Stewart, 1998;Agati and Tattini, 2010), but after acylation with phenolic acids, anthocyanins may contribute substantially to UV protection ( Fig. 3; Takahashi et al, 1991;Burger and Edwards, 1996;Tattini et al, 2014). Because acylated anthocyanins are not as common as the non-acylated forms, their UV-absorbing functions are unlikely to be a universal primary role for anthocyanins in planta (Hatier and Gould, 2009).…”