Shift in birch leaf metabolome and carbon allocation during long‐term open‐field ozone exposure

Abstract

Current and future ozone concentrations have the potential to reduce plant growth and increase carbon demand for defence and repair processes, which may result in reduced carbon sink strength of forest trees in long-term. Still, there is limited understanding regarding the alterations in plant metabolism and variation in ozone tolerance among tree species and genotypes. Therefore, this paper aims to study changes in birch leaf metabolome due to long-term realistic ozone stress and to relate these shifts in the metabolism with growth responses. Two European white birch (Betula pendula Roth) genotypes showing different ozone sensitivity were growing under 1.4-1.7 Â ambient ozone in open-field conditions in Central Finland. After seven growing seasons, the trees were analysed for changes in leaf metabolite profiling, based on 339 low molecular weight compounds (including phenolics, polar and lipophilic compounds, and pigments) and related whole-tree growth responses. Genotype caused most of the variance of metabolite concentrations, while ozone concentration was the second principal component explaining the metabolome profiling. The main ozone caused changes included increases in quercetin-phenolic compounds and compounds related to leaf cuticular wax layer, whereas several compounds related to carbohydrate metabolism and function of chloroplast membranes and pigments (such as chlorophyll-related phytol derivatives) were decreasing. Some candidate compounds such as surface wax-related squalene, 1-dotriacontanol, and dotriacontane, providing growth-related tolerance against ozone were demonstrated. This study indicated that current growth-based ozone risk assessment methods are inadequate, because they ignore ecophysiological impacts due to alterations in leaf chemistry.

Deciphering the ozone-induced changes in cellular processes: a prerequisite for ozone risk assessment at the tree and forest levels

“…Phenolic compounds are also recognized in leaf like important metabolites to cope with elevated or chronic O 3 exposure of trees (Fares et al 2010;Kontunen-Soppela et al 2007;Peltonen et al 2005;Yamaji et al 2003). For some phenolics and condensed tannins, a potential role in the O 3 tolerance has been claimed (Haikio et al 2009;Kontunen-Soppela et al 2007).…”

“…For some phenolics and condensed tannins, a potential role in the O 3 tolerance has been claimed (Haikio et al 2009;Kontunen-Soppela et al 2007). Furthermore, in accordance with an increased level in phenolics, the induction of the shikimate and phenylpropanoid pathways shared by the flavonoid, anthocyanin, tannin, stilbene and lignin biosynthesis has been well documented under O 3 exposure (see Cabané et al 2012 for review).…”

Plant Metabolomics: A Characterisation of Plant Responses to Abiotic Stresses

“…The integration of the outputs from all these different approaches allowed the authors to indicate glutamate, GABA and glutamate dehydrogenase as possible biomarkers for O 3 damages in rice. A long-term ozone exposure experiment was conducted in realistic open field conditions by Kontunen-Soppela et al (2007), to compare O 3 -induced leaf metabolome changes in two genotypes of white birch (Betula pendula Roth) differing in their ozone sensitivity. Among 339 low molecular weight metabolites, ozone enrichment led to increased concentrations of phenolic compounds (such as chlorogenic acid and quercetin glycosides) and lipophilic compounds related to leaf cuticular wax formation.…”

Global identification of potential gene biomarkers associated with ozone-induced foliar injury in rice seedling leaves by correlating their symptom severity with transcriptome profiling

“…Recently, high-throughput omics approaches (transcriptomics, proteomics and metabolomics) were applied to catalog the O3-responsive gene, protein or metabolite components in aspen (Bohler et al, 2007;Gupta et al, 2005), birch (Kontunen-Soppela et al, 2007;Ossipov et al, 2008), pepper (Lee and Yun, 2006), Arabidopsis (Mahalingam et al, 2006;Tamaoki et al, 2003), bean (Torres et al, 2007), maize (Torres et al, 2007), rice (Agrawal et al, 2002;Cho et al, 2008) and wheat (Sarkar et al, 2010). Although these, along with targeted studies, continue to refine our understanding on the O3-constitutive and -triggered signaling and metabolic responses, global identification of genes tightly associated with the symptoms of foliar injury in natural and cultivated plants remain largely unknown.…”