Metabolic responses to multi-stress: An update

Abstract

• The review addresses current advances in multifactorial stress responses focusing on metabol(om)ic changes in model and crop species • Major importance in elevated metabolite levels is given to proline and branched chain amino acids under multifactorial stress • Proline is recognized as a multifunctional molecule and homeostasis is crucial, as it helps sustain growth under prolonged stress conditions • Branched chain amino acids have recently also emerged as important stress metabolites – probably as the result of increased protein turnover under stress emerging as important alternative energy sources • A key finding from this study is that, contrary to the widespread belief—often based on phenotypes or transcriptomic data—that responses to multifactorial stresses are typically neither additive nor predictable, many changes at the metabolite level are both additive and predictable. In recent years, several studies investigating multifactorial stresses have emerged. This shift has been driven by the recognition that one of the primary reasons for the inconsistency between laboratory-based results and field observations of plant responses is that, in natural environments, plants are routinely exposed to a combination of biotic and/or abiotic stresses, which they encounter either simultaneously or sequentially. Within this review, we address current advances in multifactorial studies focusing on metabol(om)ic changes in model as well as cereal crop species. The common consensus is that currently, studies on phenotypic and transcriptomics analysis are prevailing, while metabolic studies are scarce. Despite the need for further studies to validate the findings in this review, two clear biological messages emerge. First, and perhaps unsurprisingly, proline stands out as a universal stress metabolite, closely followed by branched-chain amino acids. Interestingly, while multifactorial stress responses are often considered non-additive and unpredictable, our findings reveal that many metabolic changes are both. Expanding the scope of studies to include more species and a wider range of stresses at the metabolic level will be essential for uncovering additional metabolic reprogramming in response to multifactorial stress. This will provide invaluable insights for developing breeding strategies aimed at future-proofing crops.

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