De Novo Arginine Synthesis Is Required for Full Virulence of Xanthomonas arboricola pv. juglandis During Walnut Bacterial Blight Disease

Abstract

Walnut blight (WB) disease caused by Xanthomonas arboricola pv. juglandis (Xaj) threatens orchards worldwide. Nitrogen metabolism in this bacterial pathogen is dependent on arginine, a nitrogen enriched amino acid that can either be synthesized or provided by the plant host. The arginine biosynthetic pathway uses argininosuccinate synthase (argG), associated with increased bacterial virulence. We examined the effects of bacterial arginine and nitrogen metabolism on the plant response during WB by proteomic analysis of the mutant strain Xaj argG-. Phenotypically, the mutant strain produced 42% fewer symptoms and survived in the plant tissue with 2.5-fold reduced growth compared to wild-type (WT) while auxotrophic for arginine in vitro. Proteomic analysis of infected tissue enabled the profiling of 676 Xaj proteins and 3,296 walnut proteins using isobaric labeling in a data-dependent acquisition approach. Comparative analysis of differentially expressed proteins revealed distinct plant responses. Xaj WT triggered processes of catabolism and oxidative stress in the host under observed disease symptoms, while most host’s biosynthetic processes triggered by Xaj WT were inhibited during Xaj argG- infection. Overall, the Xaj proteins revealed a drastic shift in carbon and energy management induced by disruption of nitrogen metabolism while the top differentially expressed proteins included a Fis transcriptional regulator and a peptidyl-prolyl isomerase. Our results show the critical role of de novo arginine biosynthesis to sustain virulence and minimal growth during WB. This study is timely and critical as current copper-based control methods are losing their effectiveness, and new sustainable methods are urgently needed in orchard environments.

Transcriptome profiling of type VI secretion system core gene tssM mutant of Xanthomonas perforans highlights regulators controlling diverse functions ranging from virulence to metabolism

“…Similarly, five genes (E2P69_RS08790, E2P69_RS08775, E2P69_RS08795, E2P69_RS08780, and E2P69_RS21025) associated with the arginine biosynthesis pathway were significantly upregulated in the mutant strain at 16 hours. Arginine biosynthesis was considered a virulence trait as demonstrated by pathogenesis studies in Xanthomonadaceae species (Sagawa et al, 2022) ( 79 ) . Three genes (E2P69_RS07515, E2P69_RS19925, and E2P69_RS16500) coding for 3-phosphoshikimate 1-carboxyvinyltransferase, 3-deoxy-7-phosphoheptulonate synthase, and aminodeoxychorismate synthase component I were upregulated in the mutant strain at 8 and 16 hours, while one gene (E2P69_RS04815), which encodes for chorismate mutase, was upregulated at 8 hours in the mutant strain.…”

New Insight into Aspartate Metabolic Pathways in Populus: Linking the Root Responsive Isoenzymes with Amino Acid Biosynthesis during Incompatible Interactions of Fusarium solani

“…Ectopically expressing an ASS gene ( argG ) from Oenococcus oeni improved acid resistance in Lactobacillus , a wine strain for malolactic fermentation [ 91 ]. The recent finding suggested that bacterial ASS ( argG ) deployed the Arg biosynthetic pathway associated with increased virulence to walnut infection [ 92 ]. In mammal cells, the ASS exerts an essential role as the rate-limiting step in Asp metabolism, providing the therapeutical target used for an assortment of metabolic processes and immune responses [ 93 , 94 ].…”

Development of Real-time PCR Method for Detection of Xanthomonas campestris pv. juglandis Causing Walnut Bacterial Blight

“…The growing demand for walnut has led to the growing area of walnut cultivation, and walnut pests and diseases are becoming more frequent. Among them, walnut bacterial blight occurs continuously in many places which is widely distributed in walnut producing areas of many cities in China, and is also found in most walnut producing regions in the world (Fu et al 2021;Kim et al 2021;Sagawa et al 2021). This disease is severely harmful to walnut, affecting the healthy development of the walnut industry.…”