ISSN 0026-2617, Microbiology, 2010, Vol. 79, No. 1, pp. 58–65. © Pleiades Publishing, Ltd., 2010. Original Russian Text © M.V. Mokryakova, I.A. Abdeeva, E.S. Piruzyan, N.W. Schaad, A.N. Ignatov, 2010, published in Mikrobiologiya, 2010, Vol. 79, No. 1, pp. 63–71. 58 1 2 Bacteria of genus Xanthomonas (xanthomonads) belong to gram-negative gamma-proteobacteria and can infect nearly every cultivated plant specie causing diseases with diverse symptoms. Xanthomonads include over 25 genomospecies identified by DNA:DNA hybridization, MLST analysis, and in some cases by phenotype [1], and other 150 pathovars differed by host plant range and symptoms of the dis- eases caused [2]. Many species and pathovars of xan- thomonads are divided into numerous physiologic races recognized in scheme of gene-for-gene interac- tion by reaction of differential plants with specific resistance genes. The basic hypothesis of Flore for gene-for-gene interaction suggests that product of plant resistance gene directly or indirectly interacts with product of avirulence gene in pathogen [3]. Xan- thomonads population infecting plants of different species and families have high genetic diversity includ- ing variable patterns of avirulence genes [4]. Proteins secreted via the Type 3 Secretion System (T3SS) into host cell are one of major pathogenicity mechanisms of gram-negative bacteria [5]. Proteins, delivered by the T3SS are called T3SS effectors. The majority of effector have unknown function yet. Some known effector proteins can block signals of innate immunity pathway [6]. Entering the host cell they pre- vent development of plant reaction on non-specific elicitors—MAMPs (microbe associated metabolic 1 The article was translated by the authors. 2 Corresponding author; e-mail: marja-2007@yandex.ru profiles) [7]. Effector proteins are essential for viru- lence and host specificity of all bacteria species with T3SS [8]. Over 20 effector genes were described for xanth- omonads in previous research [9]. In a few cases they can determine race of the pathogen, in others—con- trol the pathogen aggressiveness [10]. Homologous effectors were found in bacteria of different species and genera, and horizontal transfer of them was postu- lated [6]. Publication of several complete genomes of plant pathogenic bacteria accelerated identification of new effector genes by identification of conservative promoters, specific signals and domens [11]. Eight strains of xanthomonads were sequenced and anno- tated as well at the time of this article preparation. Generally, the effector gene content was diverse even between the strains of a single species. The aim of current study was to identify content of effector genes in natural population of Xanthomonas campestris pv. campestris, crucifers pathogen, and compare the spectrum of the loci with previously stud- ied physiologic and taxonomic features of the bacteria including race and pathovar. MATERIALS AND METHODS Bacteria and Cultivation 53 strains of several species, pathovars and races of World-wide origin were obtained through the collec- tion of Russian Research Institute of Phytopathology. Identity of all bacteria was confirmed by PCR ampli- Diversity of Effector Genes in Plant Pathogenic Bacteria of Genus Xanthomonas 1 M. V. Mokryakova a, 2 , I. A. Abdeeva a , E. S. Piruzyan a , N. W. Schaad b , and A. N. Ignatov c a Vavilov Institute of General Genetics Russian Academy of Science, Moscow b USDA ARS Foreign Disease and Weed Science Research Unit, Ditto Avenue, Fort Detrick, Maryland, 21702 United States c Center “Bioengineering” Russian Academy of Science, Moscow Received February 16, 2009 Abstract—Gram-negative plant pathogenic bacteria are secreting into plant cell a special type of pathogenic- ity-related proteins called effectors. They are capable of suppressing plant innate immunity or stimulating synthesis and export of metabolites desired by the pathogen. We identified a number of effector-coding genes typical of xanthomonads analyzing 8 completely sequenced genomes of genus Xanthomonas. Using represen- tative collection provided by Russian Research Institute of Phytopathology we identified genetic diversity of effector gene loci in population of Xanthomonas bacteria. Patterns of effector genes were identified for indi- vidual strains and statistic linkage between particular genes and race of the pathogen was established. For the first time several untypical effector genes were found in strains of Xanthomonas campestris pv. campestris. Key words: bacteria, avirulence, pathogenesis, genetic diversity. DOI: 10.1134/S002626171001008X EXPERIMENTAL ARTICLES