1H HR-MAS NMR metabolomics uncovers coordinated metabolic response to water stress in transgenic Swingle citrumelo

Abstract

Understanding the biochemical mechanisms underlying drought tolerance in citrus is essential for developing rootstocks adapted to water-deficit conditions. This study applied proton high resolution magic-angle spinning nuclear magnetic resonance (1 H HR-MAS NMR) combined with chemometrics to characterize the metabolism of leaves from conventional non-transgenic (NT) and transgenic (T35S) Swingle citrumelo plants overexpressing the P5CSF129A gene, responsible for proline overproduction. This approach enabled the identification of metabolic alterations throughout stress progression. Transgenic plants exhibited constitutive proline accumulation, accompanied by coordinated modulation of choline, fatty acids, glucose, and sucrose. These adjustments reflect the involvement of nitrogen, carbon, and lipid pathways, conferring osmotic and redox stabilities and supporting the maintenance of metabolic homeostasis under severe water deficit. The combination of 1 H HR‑MAS NMR and chemometrics proved to be a robust, non-destructive chemical tool for elucidating metabolic profiles in genetically modified plants, contributing to the understanding of molecular mechanisms underlying drought tolerance in citrus and supporting the development of rootstocks better adapted to climate change. These findings support the use of 1 H HR‑MAS NMR metabolomics for elucidating drought-response mechanisms and for advancing omics-driven breeding strategies in citrus.