The RpfF Acyl-ACP thioesterase of major rice pathogen Xanthomonas oryzae pv. oryzae is essential for maintenance of membrane function and virulence
4 affiliations
- 1Guangdong Provincial Key Laboratory for the Development Biology and Environmental Adaptation of Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou, Guangdong, China.
- 2Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America.
- 3Institute of Plant Protection, Jiangxi Academy of Agricultural Sciences, Nanchang, Jiangxi, China.
- 4Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America.
Abstract
In Xanthomonas, RpfF is a bifunctional enzyme having both enoyl-ACP dehydratase and acyl-ACP thioesterase activities catalyzed by a single active site. While the dehydratase activity is essential for producing quorum-sensing signals of the diffusible signal factor (DSF) family, the physiological role of the thioesterase activity remained unclear. Singh and coworkers have reported that deletion of the gene encoding RpfF (a ∆rpfF strain) of the rice pathogen X. oryzae pv. oryzae (Xoo) resulted in loss of membrane integrity (Singh et al, 2022). We report that the loss in membrane integrity is due to lack of the RpfF thioesterase activity. This was demonstrated by restoration of membrane integrity in the ΔrpfF strain by expression of a foreign thioesterase. Thioesterases originating in either E. coli or a plant enzyme fully restored virulence in rice, bacterial growth, and tolerance of membrane stress. The thioesterase overcame the defects in membrane lipid synthesis reported previously and restored the lipid components to wild-type levels. Radiolabeling revealed that fatty acid synthesis in the ΔrpfF strain proceeded at only one-third of the wild-type rate, which was rescued by complementation with thioesterase encoding genes. Thus, the acyl-ACP thioesterase activity of RpfF is a key regulator of de novo fatty acid synthesis and membrane integrity. We propose a dual-function model wherein RpfF maintains membrane lipid homeostasis via its thioesterase activity while concurrently producing DSF signals via its dehydratase activity to orchestrate quorum sensing. Author summary: We demonstrate that the Xoo RpfF enzyme serves a dual role: it produces DSF-family quorum-sensing signals and, through its acyl-ACP thioesterase activity, maintains membrane integrity. By regulating de novo fatty acid biosynthesis, RpfF ensures an optimal phospholipid-to-LPS ratio and a balanced fatty acid profile, both critical for membrane function. Remarkably, this membrane-protective role is itself modulated by DSF-mediated quorum sensing, enabling the pathogen to coordinate virulence factor production with rapid membrane remodeling. Such adaptive capacity enhances stress tolerance and host adaptation, ultimately maximizing infectivity. RpfF function is conserved across Xanthomonas species, highlighting its broad biological and agricultural significance.
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BibTeX
@article{luo2026rpff,
title = {{The RpfF Acyl-ACP thioesterase of major rice pathogen Xanthomonas oryzae pv. oryzae is essential for maintenance of membrane function and virulence}},
author = {Lizhen Luo and Zhe Hu and Mingfeng Yan and John E Cronan and Haihong Wang},
journal = {PLOS Pathogens},
year = {2026},
month = oct,
doi = {10.1371/journal.ppat.1014669},
url = {https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1014669},
note = {CC BY},
}
RIS
TY - JOUR
TI - The RpfF Acyl-ACP thioesterase of major rice pathogen Xanthomonas oryzae pv. oryzae is essential for maintenance of membrane function and virulence
AU - Lizhen Luo
AU - Zhe Hu
AU - Mingfeng Yan
AU - John E Cronan
AU - Haihong Wang
PY - 2026
DA - 2026/10/06
JO - PLOS Pathogens
DO - 10.1371/journal.ppat.1014669
UR - https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1014669
AB - In Xanthomonas, RpfF is a bifunctional enzyme having both enoyl-ACP dehydratase and acyl-ACP thioesterase activities catalyzed by a single active site. While the dehydratase activity is essential for producing quorum-sensing signals of the diffusible signal factor (DSF) family, the physiological role of the thioesterase activity remained unclear. Singh and coworkers have reported that deletion of the gene encoding RpfF (a ∆rpfF strain) of the rice pathogen X. oryzae pv. oryzae (Xoo) resulted in loss of membrane integrity (Singh et al, 2022). We report that the loss in membrane integrity is due to lack of the RpfF thioesterase activity. This was demonstrated by restoration of membrane integrity in the ΔrpfF strain by expression of a foreign thioesterase. Thioesterases originating in either E. coli or a plant enzyme fully restored virulence in rice, bacterial growth, and tolerance of membrane stress. The thioesterase overcame the defects in membrane lipid synthesis reported previously and restored the lipid components to wild-type levels. Radiolabeling revealed that fatty acid synthesis in the ΔrpfF strain proceeded at only one-third of the wild-type rate, which was rescued by complementation with thioesterase encoding genes. Thus, the acyl-ACP thioesterase activity of RpfF is a key regulator of de novo fatty acid synthesis and membrane integrity. We propose a dual-function model wherein RpfF maintains membrane lipid homeostasis via its thioesterase activity while concurrently producing DSF signals via its dehydratase activity to orchestrate quorum sensing. Author summary: We demonstrate that the Xoo RpfF enzyme serves a dual role: it produces DSF-family quorum-sensing signals and, through its acyl-ACP thioesterase activity, maintains membrane integrity. By regulating de novo fatty acid biosynthesis, RpfF ensures an optimal phospholipid-to-LPS ratio and a balanced fatty acid profile, both critical for membrane function. Remarkably, this membrane-protective role is itself modulated by DSF-mediated quorum sensing, enabling the pathogen to coordinate virulence factor production with rapid membrane remodeling. Such adaptive capacity enhances stress tolerance and host adaptation, ultimately maximizing infectivity. RpfF function is conserved across Xanthomonas species, highlighting its broad biological and agricultural significance.
SN - 1553-7374
SN - 1553-7366
ER -