Elucidating Functions of FleQ in Xanthomonas oryzae pv. oryzae by Comparative Proteomic and Phenotypic Analyses

Abstract

To acclimate to different environments, gene expression has to be controlled using diverse transcriptional activators. FleQ activates σ54-dependent transcription initiation and regulates flagellar biosynthesis and other mechanisms in several bacteria. Xanthomonas oryzae pv. oryzae (Xoo), which is a causal agent of bacterial leaf blight on rice, lacking FleQ loses swimming motility and virulence is not altered. However, other biological mechanisms related with FleQ in Xoo are unknown. In this study, we generated the FleQ-overexpressing strain, Xoo(FleQ), and knockout mutant, XooΔfleQ. To predict the mechanisms affected by FleQ, label-free shotgun comparative proteomics was carried out. Based on proteomic results, we performed diverse phenotypic assays. Xoo(FleQ) had reduced ability to elicit disease symptoms and exopolysaccharide production. Additionally, the ability of XooΔfleQ(EV) (empty vector) and Xoo(FleQ) to form biofilm was decreased. Swarming motility of XooΔfleQ(EV) was abolished, but was only reduced for Xoo(FleQ). Additionally, abnormal twitching motility was observed in both strains. Siderophore production of Xoo(FleQ) was enhanced in iron-rich conditions. The proteomic and phenotypic analyses revealed that FleQ is involved in flagellar-dependent motility and other mechanisms, including symptom development, twitching motility, exopolysaccharide production, biofilm formation, and siderophore production. Thus, this study provides fundamental information about a σ54-dependent transcription activator in Xoo.

Mechanistic insights into host adaptation, virulence and epidemiology of the phytopathogenXanthomonas

“…harbour motility-associated apparatuses like flagella and type IV pili and motility of these bacteria in vitro was reported to be mostly attributed to flagella (Yang et al 2009;Malamud et al 2011;Tian et al 2015). It is yet to be shown if flagella directly play a role in endophytic fitness or plant surface motility but it was reported to be significant to infectivity (Malamud et al 2011;Bae et al 2018;Kumar Verma, Samal and Chatterjee 2018), suggesting that flagellar motility might play a role in the epiphytic phase.…”

“… 2011 ; Bae et al . 2018 ; Kumar Verma, Samal and Chatterjee 2018 ), suggesting that flagellar motility might play a role in the epiphytic phase.…”

A LysR-Type Transcriptional Regulator LcrX Is Involved in Virulence, Biofilm Formation, Swimming Motility, Siderophore Secretion, and Growth in Sugar Sources in Xanthomonas axonopodis Pv. glycines

“…The swimming and swarming motility assays were performed as described previously with slight modifications (Bae et al, 2018a). Swarming and swimming and motilities were determined on an XVM2 plate containing 0.3% agar.…”

Identification of c-di-GMP Signaling Components in Xanthomonas oryzae and Their Orthologs in Xanthomonads Involved in Regulation of Bacterial Virulence Expression

“…Moreover, diverse proteins and riboswitches were identified as novel c-di-GMP effectors in other pathogenic bacteria, for instance, FleQ, a transcription regulator from P. aeruginosa , and SgmT, a HK from Myxococcus xanthus (Kulshina et al, 2009; Baraquet et al, 2012; Petters et al, 2012; Tang et al, 2016; Weinberg et al, 2017). FleQ's homologs widely existed in Xanthomonads, which were the major transcriptional activators of expression of flagellar genes in Xcc and Xoo (Tian et al, 2015; Bae et al, 2018). Furthermore, Many HKs were extensively characterized for their biological functions in Xcc and Xoo (Qian et al, 2008).…”