Soil moisture and its interaction with temperature determine root metabolomes of a Himalayan alpine shrub

Abstract: Climate change profoundly impacts plants. However, our understanding of plant responses to climate largely relies on plant morphology and physiology, while plant metabolomic responses, especially those within plant roots, have received much less attention. Understanding root metabolomic variation is key to understanding cellular-level plant responses to changing climatic conditions. In this study, we investigated the individual and interactive effects of temperature and soil moisture on the root metabolome of the alpine Himalayan dwarf shrub Rhododendron anthopogon. Using an untargeted metabolomics approach, we analysed shifts in metabolomic profiles in multivariate space and identified metabolites most responsive to climatic variation. Our results revealed that soil moisture exerted the strongest influence on root metabolomic profiles, followed by the interactive effects of temperature and moisture, with temperature alone explaining the least variation. Notably, approximately 75% of metabolites significantly affected by climate responded to the interaction between temperature and moisture, suggesting that temperature effects are largely moisture-dependent. Multiple classes of primary and secondary metabolites were influenced by climate, with flavonoids, alkaloids, and triterpenoids showing the most pronounced responses. Pathway analysis indicated the presence of several climate-sensitive metabolites involved in key metabolic pathways. The most responsive metabolites were phenolics, glycosides and amino acids. These metabolites formed interconnected networks, acting as hub compounds likely playing pivotal roles in regulating plant responses to climatic variability. Our findings underscore the complex interplay between climatic factors in shaping root metabolomic profiles and suggest that climate change will impact plant health and productivity, possibly also affecting plant interactions with soil biota.