<i>Xanthomonas citri</i> subsp. <i>citri</i> Type IV Pilus Is Required for Twitching Motility, Biofilm Development, and Adherence

Dunger, Germán; Guzzo, Cristiane R.; Andrade, Maxuel O.; Jones, Jeffrey B.; Farah, Chuck S.

doi:10.1094/mpmi-06-14-0184-r

Cited by 63 publications

(117 citation statements)

References 106 publications

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“…PilR belongs to the PilS-PilR TCS, which is conserved in proteobacteria and is involved in the regulation of T4P synthesis and twitching motility (17)(18)(19). This TCS also plays a role in bacterial attachment to surfaces and biofilm formation (20)(21)(22)(23).…”

Section: Resultsmentioning

confidence: 99%

Lysobacter PilR, the Regulator of Type IV Pilus Synthesis, Controls Antifungal Antibiotic Production via a Cyclic di-GMP Pathway

Chen

Xia

et al. 2017

Appl Environ Microbiol

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Lysobacter enzymogenes is a ubiquitous soil gammaproteobacterium that produces a broad-spectrum antifungal antibiotic, known as heat-stable antifungal factor (HSAF). To increase HSAF production for use against fungal crop diseases, it is important to understand how HSAF synthesis is regulated. To gain insights into transcriptional regulation of the HSAF synthesis gene cluster, we generated a library with deletion mutations in the genes predicted to encode response regulators of the two-component signaling systems in L. enzymogenes strain OH11. By quantifying HSAF production levels in the 45 constructed mutants, we identified two strains that produced significantly smaller amounts of HSAF. One of the mutations affected a gene encoding a conserved bacterial response regulator, PilR, which is commonly associated with type IV pilus synthesis. We determined that L. enzymogenes PilR regulates pilus synthesis and twitching motility via a traditional pathway, by binding to the pilA promoter and upregulating pilA expression. Regulation of HSAF production by PilR was found to be independent of pilus formation. We discovered that the pilR mutant contained significantly higher intracellular levels of the second messenger cyclic di-GMP (c-di-GMP) and that this was the inhibitory signal for HSAF production. Therefore, the type IV pilus regulator PilR in L. enzymogenes activates twitching motility while downregulating antibiotic HSAF production by increasing intracellular c-di-GMP levels. This study identifies a new role of a common pilus regulator in proteobacteria and provides guidance for increasing antifungal antibiotic production in L. enzymogenes.

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Section: Resultsmentioning

confidence: 99%

Lysobacter PilR, the Regulator of Type IV Pilus Synthesis, Controls Antifungal Antibiotic Production via a Cyclic di-GMP Pathway

Chen

Xia

et al. 2017

Appl Environ Microbiol

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“…As described for other plant pathogenic bacteria, in planta colonization by Xtg is likely to be dependent on the type IV pilus (T4P), which mediates adherence and twitching motility [57]. A corresponding gene cluster was also identified in the other X. translucens pathovars.…”

Section: Discussionmentioning

confidence: 96%

Comparative genomics of host adaptive traits in Xanthomonas translucens pv. graminis

et al. 2017

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Background Xanthomonas translucens pathovars differ in their individual host ranges among Poaceae. As the causal agent of bacterial wilt in Italian ryegrass (Lolium multiflorum Lam.), X. translucens pv. graminis (Xtg) is one of the most important bacterial pathogens in temperate grassland regions. The genomes of six Xtg strains from Switzerland, Norway, and New Zealand were sequenced in order to gain insight into conserved genomic traits from organisms covering a wide geographical range. Subsequent comparative analysis with previously published genome data of seven non-graminis X. translucens strains including the pathovars arrhenatheri, poae, phlei, cerealis, undulosa, and translucens was conducted to identify candidate genes linked to the host adaptation of Xtg to Italian ryegrass.ResultsPhylogenetic analysis revealed a tight clustering of Xtg strains, which were found to share a large core genome. Conserved genomic traits included a non-canonical type III secretion system (T3SS) and a type IV pilus (T4P), which both revealed distinct primary structures of the pilins when compared to the non-graminis X. translucens strains. Xtg-specific traits that had no homologues in the other X. translucens strains were further found to comprise several hypothetical proteins, a TonB-dependent receptor, transporters, and effector proteins as well as toxin-antitoxin systems and DNA methyltransferases. While a nearly complete flagellar gene cluster was identified in one of the sequenced Xtg strains, phenotypic analysis pointed to swimming-deficiency as a common trait of the pathovar graminis.ConclusionOur study suggests that host adaptation of X. translucens pv. graminis may be conferred by a combination of pathovar-specific effector proteins, regulatory mechanisms, and adapted nutrient acquisition. Sequence deviations of pathogen-associated molecular patterns (PAMPs), as observed for the pilins of the T4P and T3SS, are moreover likely to impede perception by the plant defense machinery and thus facilitate successful host colonization of Italian ryegrass.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-3422-7) contains supplementary material, which is available to authorized users.

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“…However, genes coding for proteins of the T2SS general secretion pathway, as well as for proteins putatively involved in the formation of type IV pili (T4P) are present [4,54]. T4P are flexible surface filaments that are assembled through the general secretion pathway and play diverse roles, for example, in twitching motility, surface adhesion, natural transformation, biofilm formation and chemotaxis [73,74]. It has been speculated that they may provide an important function in auto-aggregation and biofilm formation for CaLas [54], but this hypothesis remains to be proved.…”

Section: Secretion Systems and Effectorsmentioning

confidence: 99%

“…In Xfa, T4P are required for obstruction of sap flow, intercellular communication, and migration of bacterial cells within the xylem [75][76][77][78]. In Xcc, it was recently shown that, like in Xfa, T4P are required for twitching motility, adhesion, and biofilm formation [74,79].…”

Section: Secretion Systems and Effectorsmentioning

confidence: 99%

Bacterial Citrus Diseases: Major Threats and Recent Progress

Jl¹

2017

JBMOA

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Citriculture is an important, highly organized, and competitive sector of the Brazilian economy. Nonetheless, citrus production is constantly threatened by pathogens that cause considerable economic losses and severe social impacts. Among the major citrus diseases are citrus canker (CCK), citrus variegated chlorosis (CVC), and Huanglongbing (HLB), caused by members of the bacterial species Xanthomonas citri (Xcc), Xylella fastidiosa (Xfa), and 'Candidatus Liberibacter' (CaL), respectively. During the last years, management practices for CVC and HLB in Brazil have provided good results, maintaining the disease incidence at low levels. In contrast, CCK re-emerged as the main citrus disease because of the inefficacy of the current eradication program. In this review, we discuss about the biology of the plant-pathogen interactions, several controversial aspects on the taxonomy of the causal agents, the molecular mechanisms they use to cause disease in citrus plants, the strategies used for disease management and their limitations, and some emerging control alternatives that may be available for commercial production in the future, including transgenic and genome-edited plants with enhanced resistance.

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Xanthomonas citri subsp. citri Type IV Pilus Is Required for Twitching Motility, Biofilm Development, and Adherence

Cited by 63 publications

References 106 publications

Lysobacter PilR, the Regulator of Type IV Pilus Synthesis, Controls Antifungal Antibiotic Production via a Cyclic di-GMP Pathway

Lysobacter PilR, the Regulator of Type IV Pilus Synthesis, Controls Antifungal Antibiotic Production via a Cyclic di-GMP Pathway

Comparative genomics of host adaptive traits in Xanthomonas translucens pv. graminis

Bacterial Citrus Diseases: Major Threats and Recent Progress

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