The root microbiome structure ensures optimal plant host health and fitness, and it is, at least in part, defined by the plant genotype. It is well documented that root-secreted amino acids promote microbial chemotaxis and growth in the rhizosphere. However, whether the plant-mediated re-uptake of amino acids contributes to maintaining optimal levels of amino acids in the root exudates, and, in turn, microbial growth and metabolism, remains to be established. Here, we show that Lysine-Histidine Transporter-1 (LHT1), an amino acid inward transporter expressed in Arabidopsis thaliana roots, limits the growth of the plant-growth-promoting bacteria Pseudomonas simiae WCS417r (Ps WCS417r). The amino acid profiling of the lht1 mutant root exudates showed increased levels of glutamine, among other amino acids. Interestingly, lht1 exudates or Gln-supplemented wild-type exudates enhance Ps WCS417r growth. However, despite promoting bacterial growth and robust root colonization, lht1 exudates and Gln-supplemented wild-type exudates inhibited plant growth in a Ps WCS417r-dependent manner. The transcriptional analysis of defense and growth marker genes revealed that plant growth inhibition was not linked to the elicitation of plant defense but likely to the impact of Ps WCS417r amino acids metabolism on auxin signaling. These data suggest that an excess of amino acids in the rhizosphere impacts Ps WCS417r metabolism, which, in turn, inhibits plant growth. Together, these results show that LHT1 regulates the amino-acid-mediated interaction between plants and Ps WCS417r and suggest a complex relationship between root-exuded amino acids, root colonization by beneficial bacteria, bacterial metabolism, and plant growth promotion.
Belowground microbiome structure ensures optimal plant-host health and fitness, and it is, at least in part, defined by the plant genotype. Root-secreted amino acids (AAs) promote microbial chemotaxis and growth in the rhizosphere. However, whether the plant-mediated reuptake of AAs contributes to maintaining optimal levels of AAs in the rhizosphere, and in turn, microbial growth, remains to be established. The Arabidopsis thaliana LHT1 is a high-affinity transporter expressed in the rhizodermis that can take up AAs from the soil. Here we show that a loss-of-function mutant for LHT1 leads to increased accumulation of plant-derived amino acids in the root exudates and that lht1 root exudates enable more growth of the plant-growth-promoting bacteria (PGPB) Pseudomonas simiae WCS417r (Ps WCS417r). Amino acid profiling of the lht1 exudates showed increased levels of glutamine (Gln) and other amino acids. Excitingly, supplementing wild-type root exudates with Gln was sufficient to promote Ps WCS417r growth. However, intriguingly, despite promoting Ps WCS417r growth, lht1 exudates and wild-type exudates supplemented with Gln inhibit plant growth in a Ps WCS417r-dependent manner. These data suggest that an excess of AAs in the rhizosphere impacts Ps WCS417r metabolism which in turn inhibits plant growth. Together, the results unveil that LHT1 regulates the amino acid-mediated interaction between plants and Ps WCS417r and suggest a complex relationship between root-exuded metabolites, PGPB, and plant growth.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.