Thiamine Is Required for Virulence and Survival of Pseudomonas syringae pv. tomato DC3000 on Tomatoes

Jun Liu; Xuejiang Zhang; Siyi Deng; Hua Wang; Youfu Zhao

doi:10.3389/fmicb.2022.903258

Thiamine Is Required for Virulence and Survival of Pseudomonas syringae pv. tomato DC3000 on Tomatoes

Front Microbiol. 2022 Jun 17:13:903258. doi: 10.3389/fmicb.2022.903258. eCollection 2022.

Authors

Jun Liu^{1

2

3}, Xuejiang Zhang^{1

2

3}, Siyi Deng^{1

2

3}, Hua Wang^{1

2

3}, Youfu Zhao⁴

Affiliations

¹ Institute of Plant Protection and Soil Fertilizer, Hubei Academy of Agricultural Sciences, Wuhan, China.
² Key Laboratory of Integrated Pest Management on Crops in Central China, Ministry of Agriculture, Wuhan, China.
³ Hubei Key Laboratory of Crop Disease, Insect Pests and Weeds Control, Wuhan, China.
⁴ Department of Plant Pathology, Irrigated Agriculture Research and Extension Center, Washington State University, Prosser, WA, United States.

Abstract

Pseudomonas syringae pv. tomato DC3000 (PstDC3000) is an important plant pathogen that infects tomatoes and Arabidopsis. Thiamine and its derivative thiamine pyrophosphate (TPP) are cofactors that play an important role in the growth and survival of many bacterial microorganisms. However, the role of thiamine-related genes has not been determined in PstDC3000. Hence, to investigate the role of TPP in growth, resistance to stresses, and virulence of PstDC3000, double and quadruple mutants of thiamine biosynthesis-related genes (thiD/E, thiS/G, and thiD/E/S/G deletion mutants) as well as a single mutant of a lipoprotein-related gene (apbE) were constructed. Our results showed that growth of the thiD/E, thiS/G, and thiD/E/S/G mutants in the mannitol-glutamate (MG) medium was significantly lower than that of the wild type (WT) and their growth could be restored to the WT level with the addition of exogenous thiamine, whereas mutation of the apbE gene did not affect its growth in vitro. While tolerance to acid, osmotic, and oxidative stresses for the double mutants was similar to the WT, tolerance to stresses for the apbE mutant was reduced as compared to the WT. In addition, all four mutants exhibited reduced virulence and growth in tomatoes. However, when the double and quadruple mutants were inoculated with exogenous thiamine, the virulence and growth rate of these mutants were restored to the WT level. These results indicated that the thiD/E, thiS/G, and thiD/E/S/G mutants exhibiting growth deficiency in planta are probably due to a lack of thiamine biosynthesis, thus reducing colonization in tomatoes. On the other hand, it is possible that the apbE mutant exhibited reduced stress tolerances, thus resulting in reduced colonization. Overall, our findings suggest that the thiamine biosynthetic (TBS) pathway plays an important role in the colonization and infection of PstDC3000. Therefore, the thiamine biosynthetic pathway could be used as the target to develop new control measures for a bacterial spot in tomatoes.

Keywords: Pseudomonas syringae pv. tomato DC3000; cell growth; stress tolerance; thiamine; virulence.