COMPARATIVE GENOMIC AND PHENOTYPIC ANALYSIS OF THREE Xanthomonas vesicatoria STRAINS WITH DIFFERENT DEGREES OF AGGRESSIVENESS ON TOMATO.

BIANCO MI; CONFORTE VP; VOJNOV AA; GARITA-CAMBRONERO J; DUNGER G; ROMERO AM; PONSO A; CUBERO J; MORALES G; YARYURA PM

Congreso; https://samige.org.ar/congresos-anteriores/; 2022

Xanthomonas vesicatoria (Xv) is a member of a complex of species that causes bacterial spot on tomato (Solanum lycopersicum), a disease that affects different plant crops worldwide causing fruit quality decrease and also loss of entire crop production. Bacterial spot is generally controlled using copper-based agrochemicals, which contaminate the environment and have led to the emergence of copper-resistant Xanthomonas spp. strains. Therefore, to develop sustainable alternative controlstrategies for bacterial spot, it is essential to understand the pathogenic mechanisms used by these bacteria to infect their hosts. In Argentina, bacterial spot is found in all tomato-producing areas, being Xv one of the main species detected in the fields. Currently, little is known about several virulencefactors of Xv. Previously, we isolated three native strains of Xv (BNM208, BNM214 and BNM216) from diseased tomato plants, which showed different aggressiveness degrees on tomato plants. We observed that the most aggressive strain, BNM208, formed a homogeneous, compact and well- structured biofilm and produced a significantly more viscous xanthan compared with the biofilms formed by BNM214 and BNM216. Therefore, to elucidate the causes of these differences, wesequenced genomes of the three strains, compared them with each other and with 12 other Xv genomes, and analyzed groups of genes encoding virulence factors in other phytopathogenic Xanthomonas spp., focusing our studies on xanthan and T4P. We did not find differences among the three strains in the gene cluster encoding xanthan production; however, the microscopically observations of the respective xanthans showed that BNM208 produced larger molecules thanBNM214 and BNM216. This could be related to the higher expression of GumC (protein involved in xanthan polymerization) in BNM208 than in BNM214 and BNM216. Moreover, the three strains moved by twitching, a movement depending on T4P, and contain in their genomes Xac3805-like gene (encoding for major pilin in Xanthomonas campestris). Interestingly, only BNM208 contains a Xac3241-like gene (encoding for major pilin in Xanthomonas citri). The main pilin(s) of the T4P of Xv is not known at this time: therefore, we suggest that probably the Xac3805-like gene could encode the major pilin in Xv, but to confirm this, further studies are required.