Biosynthesis of Amino Acids in Xanthomonas oryzae pv. oryzae Is Essential to Its Pathogenicity

Xanthomonas oryzae pv. oryzae (Xoo) is the causal agent of rice bacterial blight disease, which causes a large reduction in rice production. The successful interaction of pathogens and plants requires a particular nutrient environment that allows pathogen growth and the initiation of both pathogen and host responses. Amino acid synthesis is essential for bacterial growth when bacteria encounter amino acid-deficient environments, but the effects of amino acid synthesis on Xoo pathogenicity are unclear. Here, we systemically deleted the essential genes (leuB, leuC, leuD, ilvC, thrC, hisD, trpC, argH, metB, and aspC) involved in the synthesis of different amino acids and analyzed the effects of these mutations on Xoo virulence. Our results showed that leucine, isoleucine, valine, histidine, threonine, arginine, tryptophan, and cysteine syntheses are essential to Xoo infection. We further studied the role of leucine in the interaction between pathogens and hosts and found that leucine could stimulate some virulence-related responses and regulate Xoo pathogenicity. Our findings highlight that amino acids not only act as nutrients for bacterial growth but also play essential roles in the Xoo and rice interaction.