A vitamin B 3 –driven root bacterial metabolite primes systemic immunity in Arabidopsis
- Xuemei Wang
- Peng Jiang
- Xindan Xu
- Jingfang Zhang
- Guiyang Xia
- Wenhan Qian
- Qingwen Chen
- Jin-Wei Wei
- Zhuo Liu
- Lingyun Liu
- Fengxia Zhang
- Lei Li
- Sheng Lin
- Yang Bai
- Guodong Wang
2026-08-26
The microbiota is being increasingly recognized for its ability to regulate host physiology through the production of small bioactive molecules. However, how host-derived nutrients are metabolically transformed by root-associated microbes to influence plant immunity remains poorly understood. Here, we show that vitamin B 3 (VB 3 ; niacin) secreted by plant roots shapes the assembly of a functionally specialized root microbiota, which, in turn, metabolizes VB 3 into an immune-active signal that enhances plant disease resistance. VB 3 secretion selectively increases the abundance of root-associated bacteria harboring a conserved nic biosynthetic gene cluster (BGC), which enables the conversion of VB 3 into 6-hydroxynicotinate (6-OHNA), a previously uncharacterized microbial metabolite involved in plant-microbe interactions. Microbially produced 6-OHNA is transported from roots to shoots, where it primes systemic immune responses in a salicylic acid–dependent manner. Disruption of the microbial nic BGC abolishes immune priming, whereas increased VB 3 exudation from plant roots enhances disease resistance. Together, these findings reveal a metabolically mediated dialog between plant hosts and their microbiota that links host nutrient secretion to microbial functional specialization and the activation of systemic plant immunity.