PGPHL mediates Burkholderia-induced plant growth promotion in citrus
In this study, we identified 3-oxo-C8-HSL (PGPHL) as a key AHL facilitating plant growth promotion by Burkholderia sp. strain Burk_2H3 in citrus. Metabolomic profiling revealed significantly higher accumulation of PGPHL in Burk_2H3 secretions compared to non-plant-growth-promoting Burkholderia sp. strains. Exogenous application of PGPHL, but not other Burk_2H3 secretory metabolites, markedly enhanced citrus growth. Transcriptomic analysis demonstrated that Burk_2H3 inoculation, its secretions, or PGPHL treatment consistently upregulated root transporter genes associated with mineral elements (e.g. N, P, K) acquisition. This molecular response correlated with significantly increased tissue concentrations of these elements in treated plants, suggesting enhanced root nutrient uptake as the underlying mechanism. Importantly, field trials demonstrated the translational potential of PGPHL, showing increased biomass not only in citrus but also in horticultural crops including pepper (Capsicum annuum), celery (Apium graveolens), and mustard (Brassica juncea). Our findings position 3-oxo-C8-HSL as a promising candidate for developing next-generation plant growth stimulants and biofertilizers.