Hormones as go‐betweens in plant microbiome assembly

Abstract

Summary The interaction of plants with complex microbial communities is the result of co‐evolution over millions of years and contributed to plant transition and adaptation to land. The ability of plants to be an essential part of complex and highly dynamic ecosystems is dependent on their interaction with diverse microbial communities. Plant microbiota can support, and even enable, the diverse functions of plants and are crucial in sustaining plant fitness under often rapidly changing environments. The composition and diversity of microbiota differs between plant and soil compartments. It indicates that microbial communities in these compartments are not static but are adjusted by the environment as well as inter‐microbial and plant–microbe communication. Hormones take a crucial role in contributing to the assembly of plant microbiomes, and plants and microbes often employ the same hormones with completely different intentions. Here, the function of hormones as go‐betweens between plants and microbes to influence the shape of plant microbial communities is discussed. The versatility of plant and microbe‐derived hormones essentially contributes to the creation of habitats that are the origin of diversity and, thus, multifunctionality of plants, their microbiota and ultimately ecosystems.

Good and bad lettuce leaf microbes? Unravelling the genetic architecture of the microbiome to inform plant breeding for enhanced food safety and reduced food waste

“…Hormone signalling, defence response and response to stress were also significantly overrepresented, with auxin- and ethylene-responsive genes identified within all candidate regions investigated. Phytohormones are widely recognised to have crucial roles in plant defence response to biotic stressors, regulating the colonisation of both beneficial and pathogenic microbes (Eichmann et al , 2021). The ethylene-mediated pathway is associated with plant response to necrotrophic pathogens and the inhibition of leaf growth and cell division in response to abiotic stress (Dubois et al , 2018).…”

“…Ethylene and auxin have been demonstrated to have antagonistic effects on abscisic acid-induced stomata closure (Tanaka et al , 2006). Endogenous application of auxin (indole acetic acid) to Streptomyces strains isolated from Arabidopsis roots elicited antibacterial activity towards Escherichia coli and Bacillus subtilis , providing evidence for a “cry for help” mechanism, whereby plants produce phytohormones to stimulate antibiotic production of their inhabiting microbiota (van der Meij et al , 2018; Eichmann et al , 2021). Leucine-rich repeat domain- and lectin domain-containing proteins are important in the perception of microbe-/pathogen- and damage-associated molecular patterns (MAMPs/PAMPs/DAMPs), recognising carbohydrate structures derived from microbes (MAMPs or PAMPs) or host carbohydrates, like those comprising the cell wall, which result from pathogen attack (DAMPs), triggering an immune response (Lannoo & Van Damme, 2014).…”

The plant microbiota: composition, functions, and engineering

“…Indeed, microbes that live in symbiosis with roots have long been recognized as being beneficial to plants, long before the omics era, as with mycorrhizal fungi and nitrogen-fixing bacteria (reviewed extensively in [1,26]). In addition, a plethora of plant growth-promoting bacteria improve plant nutrition and growth under limiting conditions [27] due to their capacity to mobilize nutrients (phosphorus, potassium, zinc), fix nitrogen asymbiotically, release siderophores, and interfere with plant hormone metabolism or produce phytohormones [28].…”

Synergistically promoting plant health by harnessing synthetic microbial communities and prebiotics

“…Shaping the microbial community (sculpting microbiomes) can also be directed toward the microbial community by changing the metabolites or other chemical substances secreted by the root system. For example, salicylic acid secreted by roots shapes microbial communities in a targeted manner (Eichmann et al, 2021). Different advanced and traditional approaches have been introduced to assess the diversity and functions of soil microbiota.…”