Genotype determines Arbutus unedo L. physiological and metabolomic responses to drought and recovery

Abstract

Strawberry tree (Arbutus unedo) is a small resilient species with a circum-Mediterranean distribution, high ecological relevance in southern European forests and with several economical applications. As most orchards are usually installed on marginal lands where plants usually face severe drought, selecting plants that can better cope with water restriction is critical, and a better understanding of the tolerance mechanisms is required. Strawberry tree plants under drought follow a typical isohydric strategy, by limiting transpiration through stomata closure. However, the contribution of genotype and its bio-geographic origin on plant performance needs clarification, as well as the involvement of a specific metabolic reactions associated with the mechanical response. To test this hypothesis, several eco-physiological and biochemical parameters were assessed on different genotypes, and the metabolic profiles studied, including important stress-related phytohormones, on plants under different water regimes (plants watered to 70% and 18% field capacity) and a recovery assay. A contrasting drought tolerance was found in plants from different genotypes, associated with physiological and metabolic responses. Metabolomics revealed more than 500 metabolic features were differentially accumulated, including abscisic and salicylic acids, for the genotype with better performance under drought (A4). This genotype also recovered faster when the imposed stress was interrupted, thus indicating the relevance of metabolic adaptation under water deficit conditions. By correlating carbon assimilation with identified metabolites, some proved to be satisfactory predictors of plant performance under drought and might be used for marker assisted breeding. Therefore, our study proves the importance of genotype as a major selection criterion of resistant plants to drought and provides empirical knowledge of the metabolic response involved. We also hypothesized the involvement of phenolics on response mechanisms under drought, which is worth to be explored to shed light on the metabolic pathways involved in plant response to water stress.

Priming Grapevines through Oregano Essential Oil Vapour Results in a Metabolomic Shift Eliciting Resistance against downy mildew

“…Robotised high-throughput ethanol extractions were employed to obtain semi-polar metabolites from 10 mg of freeze-dried ground leaves, as previously described (Luna et al, 2020). Untargeted metabolic pro ling by UHPLC-high resolution mass spectrometry (LCMS) was performed as described previously (Dussarrat et al, 2022;Martins et al, 2022) using an Ultimate 3000 ultra-high-pressure liquid chromatography (UHPLC) system coupled to an LTQ-Orbitrap Elite mass spectrometer interfaced with an electrospray (ESI) ionisation source (ThermoScienti c, Bremen, Germany). Reverse-phase chromatographic separation, negative ionisation, and MS settings were detailed in a previous study (Martins et al, 2022).…”

“…Untargeted metabolic pro ling by UHPLC-high resolution mass spectrometry (LCMS) was performed as described previously (Dussarrat et al, 2022;Martins et al, 2022) using an Ultimate 3000 ultra-high-pressure liquid chromatography (UHPLC) system coupled to an LTQ-Orbitrap Elite mass spectrometer interfaced with an electrospray (ESI) ionisation source (ThermoScienti c, Bremen, Germany). Reverse-phase chromatographic separation, negative ionisation, and MS settings were detailed in a previous study (Martins et al, 2022). The LCMS analytical sequence included 950 sample runs (610 unique biological samples, 167 technical duplicates, and 2 technical triplicates), 70 biological standards (prepared by mixing sample powders of camelina material to constitute a biological pool used for data interoperability), and 120 extraction blanks (prepared without plant material and used to rule out potential contaminants detected by untargeted metabolomics).…”

“…QC samples were injected every 12 samples (108 in total) and used for untargeted metabolomics for i) the correction of signal drift during long batches and ii) the calculation of coe cients of variation for each metabolomic feature so only the most robust ones are retained for chemometrics (Broadhurst et al, 2018). Brie y, MS1 full scan acquisitions at high resolution (240k) were performed on 6 QC samples for exact mass measurements, and all samples were subjected to MS2 Data Dependent Analysis (DDA, 30k resolution) to generate fragmentation information for further annotation (Martins et al, 2022).…”

Next-Generation Sequencing (NGS) Identified Species-Specific SSR and SNP Markers, Allow the Unequivocal Identification of Strawberry Tree (Arbutus unedo L.) Germplasm Accessions and Contribute to Assess Their Genetic Relationships

“…All this research activity has led to the publication of several reviews on this wide topic [ 10 , 11 ]. The relationship between the chemical and biochemical content of the leaves and the physiological response of the plants to abiotic stress was recently assessed [ 12 ].…”