Effects of quorum sensing and quorum quenching mediated by AHLs on plant-rhizosphere microbial interactions

The rhizosphere is a unique environment that arises from the interaction between plant roots and soil microorganisms. The metagenome of the microbial community in the rhizosphere plays a crucial role in shaping the plant microbiome. The interaction between plants and rhizosphere microorganisms is a complex process. In the rhizosphere environment, the microbial community recruits specific microorganisms through intricate signaling mechanisms within and between species. This coordination and control of the mixed community ultimately impacts the growth, development and health of plants. From an academic perspective, rhizosphere signaling mechanisms can be categorized into three primary types. Firstly, plants transmit signals to microorganisms by secreting low molecular weight molecules. Secondly, there is inter- and intraspecific microbial signaling. Lastly, microorganisms transmit signals to plants through compounds they produce. Rhizosphere microbes utilize quorum sensing (QS) to autonomously generate and release distinct signaling molecules, enabling them to detect variations in their concentrations and thereby regulate microbial quorum behavior. QS is a bacterial intercellular communication mechanism that regulates the expression of numerous bacterial genes, which are involved in various plant-microbe interactions. These interactions encompass functions such as biofilm formation, nitrogen fixation, hydrolysis, enzyme and extracellular polysaccharide synthesis, toxin production, cell movement, and intercellular connectivity. QS systems are characterized by the synthesis and release of specific signaling molecules. This process is crucial in rhizosphere communication as it enables the transmission of inter- and intraspecific information through the necessary signaling molecules. Due to the high density and diversity of rhizosphere bacteria, the rhizosphere may facilitate the transmission of QS signals. Additionally, these signaling molecules aid in the colonization of plant root surfaces or other rhizosphere-related areas by rhizosphere bacteria through gene expression mediated by QS. Recent research has revealed the presence of N-acyl-homoserine lactones (AHLs), diketopiperazines, diffusible signaling factor, secondary metabolites, phytohormonelike molecules and other QS signaling molecules in rhizosphere soil bacteria. AHLs are the most extensively studied quorum sensing signaling molecules in bacteria. They not only mediate bacterial quorum sensing, but also have a significant impact on the interaction between plants and rhizosphere microorganisms. This includes the colonization of rhizosphere microorganisms, the maintenance of soil ecosystems and the effects on plant growth. An in-depth understanding of the quorum sensing mechanism mediated by AHLs holds significant importance in promoting agricultural production, enhancing plant health, and fostering sustainable development. This article presents a review of the quorum sensing mechanism mediated by AHLs and discusses the regulatory role of AHLs in the interaction between plants and rhizosphere microorganisms. It explores the beneficial effects of AHLs on plant growth and development, stress tolerance and disease resistance, as well as the harmful effects of rhizosphere pathogenic bacteria on plants due to AHLs-mediated regulation of the QS system. Additionally, the article explores the impact of AHLs-based quorum quenching on plant-rhizosphere microbial interactions, aiming to provide valuable insights for plant health and agricultural production. The article also proposes new ideas and methods to promote the development of sustainable agriculture.