Functional identification of 3-hydroxyacyl-ACP dehydratase gene XoofabZ in Xanthomonas oryzae pv. oryzae

Abstract:

[Background] Bacterial leaf blight caused by Xanthomonas oryzae pv. oryzae (Xoo) is the most serious bacterial disease in rice production. Fatty acid synthesis is one of the most important basic metabolisms in bacteria, essential for cell growth, and the synthesis of membrane phospholipid and bioactive substances. However, little is known about the functions of fatty acid synthesis-related genes in Xoo. [Objective] This study aims to investigate whether the gene PXO_01118 (XoofabZ) in the genome of Xoo strain PXO99A encodes 3-hydroxyacyl-ACP dehydratase and participates in de novo fatty acids synthesis, providing new insights into the prevention and control of bacterial leaf blight in rice. [Methods] The protein activity of XooFabZ was analyzed through allogeneic genetic complementation and in vitro enzyme activity detection. Further, genetic analysis of XoofabZ was conducted using homologous recombination principles. The pathogenicity of the replacement mutant strains to the host rice (Oryza sativa L. ssp. Japonica cultivar Nipponbare) was detected by leaf clipping. [Results] Combining allogeneic genetic complementation and in vitro enzyme activity detection to demonstrate that XooFabZ exhibits 3-hydroxyacyl-ACP dehydratase activity in the initiation and dehydration reactions of fatty acid synthesis. It was not possible to directly obtain XoofabZ gene knockout mutants, indicating that XoofabZ is an essential gene in Xoo. The pathogenicity of Escherichia coli EcfabZ gene replacement mutant strains on the host rice was significantly reduced. [Conclusion] XoofabZ is an essential gene in Xoo, encoding 3-hydroxyacyl-ACP dehydratase, participating in de novo fatty acids synthesis reactions, and the formation of pathogenicity in Xoo.