Rhizospheric crosstalk: A mechanistic overview of how plant secondary metabolites alleviate abiotic stresses

Abstract

Plants often encounter incompatible growing conditions, such as drought, extreme temperatures, salinity, and heavy metals, which negatively impact their growth and development, resulting in reduced yield and, in severe cases, plant death. These stresses trigger the synthesis of plant secondary metabolites (PSMs), which help plants develop strategies to deter enemies, combat pathogens, outcompete competitors, and overcome environmental restraints. PSMs are released into the rhizosphere and play crucial roles in plant defense and communication. The multifunctionality of PSMs offers new insights into the plant intricate adaptive responses, which can refine our understanding of plant tolerance mechanisms in challenging environments. Thus, elucidating the chemical composition and functions of plant-derived specialized metabolites in the rhizosphere is the key to understanding interactions in this belowground environment. In this review, we aim to elucidate how PSMs exudation shapes the activities and abundance of the rhizosphere microbiome. We also highlight key environmental factors that regulate the structure and diversity of microbial communities. Finally, we discuss various preventive roles of PSMs, exploring how plants recruit microbes preemptively to mitigate diverse abiotic stresses. Additionally, we emphasize the significant contribution of phenolic compounds to the antioxidant defense response in plants, regulated through the shikimate pathway and is considered as a distinctive plant stress resilience component as compared to other PSMs under abiotic stress. Collectively, this study reveals the significance of understanding the multifaceted crosstalk between PSMs and the microbiome, which will facilitate the potential for developing methods to manipulate PSMs-microbiome interaction with predictive outcomes for sustainable crop production.