Plants and microbial symbiosis
Plants and microbes coinhabit the earth and have coevolved during millenia of environmental changes over time. Root metabolites are the key to mediating the dynamic association between plants and microbes, yet the underlying functions and mechanisms behind this remain largely illusive.
We synthesize recent advances connecting environmental stresses, the root metabolome and microbiota, and propose integrated synthetic biology-based strategies for tuning the plant root metabolome in situ for microbe-assisted stress resistance, offering solution to biotic, and abiotic stresses.
Fig. 1 Overview of the stress–metabolome–microbiota (SMM) sequence in plant roots. Plants can sense various abiotic and biotic stress signals, which induce the increased production of corresponding secondary metabolites. These key signaling metabolites can modulate root microbiota, enriching or repelling certain bacteria or fungi, which aid in mitigating the environmental stresses that plants have been subject to. Key stress-responsive metabolites (ranging from terpenes and benzoxazinoids to flavones and coumarins) produced by a variety of plant species and their modulated microbes are depicted corresponding to the stress conditions. Amongst the listed stress conditions, only a few SMM sequences are relatively clear. The majority of stress-responsive metabolites produced by different plants and the corresponding microbes modulated by these metabolites have not yet been identified under stress conditions. The missing components in the SMM sequences are indicated with question marks. Sequences that are unknown are indicated with dotted arrows. Note that the two major plants depicted in this figure represent monocot and dicot plants, which produce vastly diverse specialized metabolites in response to environmental stresses on a species to species basis
https://nph.onlinelibrary.wiley.com/doi/pdf/10.1111/nph.17908
Next Generation DNA Sequencing
97% of all DNA bacterial based
50% Pseudomonas species
Hyphomicrobiales – fix Nitrogen in plant available form
Sphingomonodales – remediate soil and initiate plant defense mechanisms in presence of pathogens
Rhodospirilalles – accumulate phosphates, produce pigments, vitamins and plant growth promoting substances
Burkholderiales – solubilize phosphates, fix nitrogen, degrade soil contaminants and suppress soil-borne pathogens
Rhodocycliades – denitrify, degrade organic compaounds to support plant growth and health
Nitrosomonodales – oxidise ammonia to nitrites to feed hyphomicrobiales
32% Actinomycetota species.
Streptomyces – produce antibiotics, stimulate plant immune systems, produce plant growth hormones and improve resistance to stresses
Streptosporangiales – anti-microbial activity suppressing phytopathogens
Micromonosporiales – produce antibiotics, protect plant cells from pathogenic infection
Micrococcales – degrade aromatic compounds in soil, produce antibiotics
Mycobacteriales – break down organic matter
11% Bacillus species
Bacillales – produce insect and nematode toxins, induce systemic resistance in plants, produce biofilms and peptides to help plants tolerate stress
Eubacteriales – recycle carbon, nitrogen and phosphoroues