Author:
Agorsor Israel D. K.,Kagel Brian T.,Danna Cristian H.
Abstract
ABSTRACTThe 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 LHT1, an amino acid inward transporter expressed inArabidopsis thalianaroots, limits the growth of the plant-growth-promoting bacteriaPseudomonas simiaeWCS417r (PsWCS417r). Amino acid profiling of thelht1mutant root exudates showed increased levels of glutamine, among other amino acids. Interestingly,lht1exudates or Gln-supplemented wild-type exudates enhancePsWCS417r growth. However, despite promoting bacterial growth and robust root colonization,lht1exudates and Gln-supplemented wild-type exudates inhibited plant growth in aPsWCS417r-dependent manner. 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 ofPsWCS417r amino acids metabolism on auxin signaling. These data suggest that an excess of amino acids in the rhizosphere impactsPsWCS417r metabolism which in turn inhibits plant growth. Together, these results unveil that LHT1 regulates the amino acid-mediated interaction between plants andPsWCS417r and suggest a complex relationship between root-exuded amino acids, root colonization by beneficial bacteria, bacterial metabolism, and plant growth promotion.
Publisher
Cold Spring Harbor Laboratory