Characterization of three long-chain 3-ketoacyl- acyl carrier protein (ACP) synthase homologous proteins in Xanthomonas oryzae pv. oryzae

Xanthomonas oryzae pv. oryzae ( Xoo ) is the leading bacterial cause of leaf blight disease. The activity and expression level of fatty acid synthase genes significantly affects the production of diffusible signal factor (DSF) family signals, which can regulate the production of virulence-related factors. However, the knowledge of Xoo fatty acid synthesis is quite limited. After searching the Xoo PXO99 A genome, we found that, two genes (PXO_02711 and PXO_02883) were predicted to encode 3-ketoacyl-ACP synthase II (FabF), while PXO_03137 was annotated as encoding 3-ketoacyl-ACP synthase I (FabB). In this study, we reported that FabB is involved in unsaturated fatty acid synthesis but is not essential for unsaturated fatty acid production. PXO_02711 encoding FabF1 participates in fatty acid synthesis and acts as a key enzyme in regulating fatty acid synthesis in Xoo to maintain the membrane integrity and responds to environmental stresses. In addition, Xoo exhibits inherent cerulenin resistance due to the insensitivity of its FabF1 protein. FabF2 lacks long-chain 3-ketoacyl-ACP synthase activity but may be involved in xanthomonadin synthesis.