Growth under high light and elevated temperature affects metabolic responses and accumulation of health-promoting metabolites in kale varieties

Plants are highly sensitive to changes in the light environment and respond to alternating light conditions by coordinated adjustments in foliar gene expression and metabolism. Here we assessed how long-term growth under high irradiance and elevated temperature, a scenario increasingly associated with the climate change, affects foliar chemical composition of Brassicaceous plants. Transcript profiling of Arabidopsis suggested up-regulation of phenylpropanoid metabolism and down-regulation of processes related to biotic stress resistance and indole glucosinolates (GSL). These observations prompted metabolite profiling of purple (Black Magic) and pale green (Half Tall) varieties of kale, an economically important crop species. Long-term acclimation to high light and elevated temperature resulted in reduced levels of 4-methoxy-indol-3-yl-methyl GSL in both kale varieties. The total levels of aliphatic GSLs increased under these conditions, although the profiles of individual GSL structures showed cultivar-dependent differences. Black Magic became rich in 4-methylsulfinylbutyl GSL and 2-phenylethyl GSL, which have health-promoting effects in human diet. Additionally, the purple pigmentation of Black Magic became intensified due to increased accumulation anthocyanins, especially derivatives of cyanidin. These findings demonstrate that the potentially stressful combination of high light and elevated temperature can have beneficial effects on the accumulation of health-promoting metabolites in leafy vegetables.