The complete genome sequence of Xanthomonas albilineans provides new insights into the reductive genome evolution of the xylem-limited Xanthomonadaceae

Abstract

BackgroundThe Xanthomonadaceae family contains two xylem-limited plant pathogenic bacterial species, Xanthomonas albilineans and Xylella fastidiosa. X. fastidiosa was the first completely sequenced plant pathogen. It is insect-vectored, has a reduced genome and does not possess hrp genes which encode a Type III secretion system found in most plant pathogenic bacteria. X. fastidiosa was excluded from the Xanthomonas group based on phylogenetic analyses with rRNA sequences.ResultsThe complete genome of X. albilineans was sequenced and annotated. X. albilineans, which is not known to be insect-vectored, also has a reduced genome and does not possess hrp genes. Phylogenetic analysis using X. albilineans genomic sequences showed that X. fastidiosa belongs to the Xanthomonas group. Order of divergence of the Xanthomonadaceae revealed that X. albilineans and X. fastidiosa experienced a convergent reductive genome evolution during their descent from the progenitor of the Xanthomonas genus. Reductive genome evolutions of the two xylem-limited Xanthomonadaceae were compared in light of their genome characteristics and those of obligate animal symbionts and pathogens.ConclusionThe two xylem-limited Xanthomonadaceae, during their descent from a common ancestral parent, experienced a convergent reductive genome evolution. Adaptation to the nutrient-poor xylem elements and to the cloistered environmental niche of xylem vessels probably favoured this convergent evolution. However, genome characteristics of X. albilineans differ from those of X. fastidiosa and obligate animal symbionts and pathogens, indicating that a distinctive process was responsible for the reductive genome evolution in this pathogen. The possible role in genome reduction of the unique toxin albicidin, produced by X. albilineans, is discussed.

Genomic Insights into Xylella fastidiosa Interactions with Plant and Insect Hosts

“…8.1); the relationship between X. fastidiosa, Xanthomonas albilineans, and the remainder of Xanthomonas species is unclear, but the most comprehensive published analysis identifies X. albilineans as an outgroup with low confidence (Rodriguez et al 2012). Our own analysis supports this relationship, but Xylella has also been inferred to be the sister clade to Xanthomonas albilineans (Pieretti et al 2009). The family Xanthomonadaceae is very diverse, but there is no indication that plant association is common outside of Xanthomonas and Xylella.…”

Estudos estruturais de enzimas da via de biossíntese de folatos de <i>Xanthomonas albilineans</i> para o desenvolvimento de novos candidatos a agroquímicos para a cultura de cana-de-açúcar

“…A Xanthomonas albilineans, agente causador da escaldadura das folhas, é uma bactéria gram-negativa da família Xanthomonadaceae, pertencente à ordem Xanthomonadales da subdivisão gama do filo Proteobacteria (Figura 6)._ [25][26] Morfologicamente, a X. albilineans apresenta o formato de bastão alongado, uniflagelada, não esporulante, aeróbica, crescimento lento, aspecto amarelado e colônias não mucoidais.…”

“…26 Stenotrophomonas spp e Xylella spp confirmou que, embora exista alta relação entre estes, ainda é possível diferenciar X. campestres, X. axonopodis e X. albilineans em um subgrupo mais específico. 28 Esta observação, aliada à comparação dos genes constitutivos ihfA e efp, sugerem que a X. albilineans foi um intermediário evolutivo entre diversas espécies de…”

“…26 Outro mecanismo comum às espécies fitopatogênicas e ausente na X. albilineans é a biossíntese de goma xantana. Alternativamente, a X. albilineans incorporou o cluster de genes SPI-1-T3SS (do inglês, Salmonella pathogenicity island-1 type three secretion system) comumente presente em bactérias patogênicas de animais.…”

“…A elucidação do genoma de X. albilineans forneceu valiosas informações sobre rotas biossintéticas e sobre as proteínas envolvidas nesses processos, 26 oferecendo oportunidades científicas para o desenvolvimento de novas formas de controle da doença.…”