Development of a tomato xylem-mimicking microfluidic system to study biofilm formation.

The bacterial wilt pathogen colonizes plant xylem vessels and blocks the flow of xylem sap by its biofilm (comprising of bacterial cells and extracellular material), resulting in devastating wilt disease across many economically important host plants including tomatoes. The technical challenges of imaging the xylem environment, along with the use of artificial cell culture plates and media in existing systems, limit the understanding of biofilm formation and its infection dynamics. In this study, we designed and built a microfluidic system that mimicked the physical and chemical conditions of the tomato xylem vessels, and allowed us to dissect responses to different xylem-like conditions.

Balanced callose and cellulose biosynthesis in Arabidopsis quorum-sensing signaling and pattern-triggered immunity.

The plant cell wall (CW) is one of the most important physical barriers that phytopathogens must conquer to invade their hosts. This barrier is a dynamic structure that responds to pathogen infection through a complex network of immune receptors, together with CW-synthesizing and CW-degrading enzymes. Callose deposition in the primary CW is a well-known physical response to pathogen infection.

Potentiation of plant defense by bacterial outer membrane vesicles is mediated by membrane nanodomains.

Outer membrane vesicles (OMVs) are released from the outer membranes of Gram-negative bacteria during infection and modulate host immunity during host-pathogen interactions. The mechanisms by which OMVs are perceived by plants and affect host immunity are unclear. Here, we used the pathogen Xanthomonas campestris pv.

Formin nanoclustering-mediated actin assembly during plant flagellin and DSF signaling.

Plants respond to bacterial infection acutely with actin remodeling during plant immune responses. The mechanisms by which bacterial virulence factors (VFs) modulate plant actin polymerization remain enigmatic. Here, we show that plant-type-I formin serves as the molecular sensor for actin remodeling in response to two bacterial VFs: Xanthomonas campestris pv.

The bacterial quorum sensing signal DSF hijacks sterol biosynthesis to suppress plant innate immunity.

Quorum sensing (QS) is a recognized phenomenon that is crucial for regulating population-related behaviors in bacteria. However, the direct specific effect of QS molecules on host biology is largely understudied. In this work, we show that the QS molecule DSF (-11-methyl-dodecenoic acid) produced by pv.

Salicylic acid-mediated plasmodesmal closure via Remorin-dependent lipid organization.

Plasmodesmata (PD) are plant-specific membrane-lined channels that create cytoplasmic and membrane continuities between adjacent cells, thereby facilitating cell-cell communication and virus movement. Plant cells have evolved diverse mechanisms to regulate PD plasticity in response to numerous environmental stimuli. In particular, during defense against plant pathogens, the defense hormone, salicylic acid (SA), plays a crucial role in the regulation of PD permeability in a callose-dependent manner.

A Single Regulator Mediates Strategic Switching between Attachment/Spread and Growth/Virulence in the Plant Pathogen .

The PhcA virulence regulator in the vascular wilt pathogen responds to cell density via quorum sensing. To understand the timing of traits that enable to establish itself inside host plants, we created a Δ mutant that is genetically locked in a low-cell-density condition. Comparing levels of gene expression of wild-type and the Δ mutant during tomato colonization revealed that the PhcA transcriptome includes an impressive 620 genes (>2-fold differentially expressed; false-discovery rate [FDR], ≤0.

Extracellular DNases of Ralstonia solanacearum modulate biofilms and facilitate bacterial wilt virulence.

Ralstonia solanacearum is a soil-borne vascular pathogen that colonizes plant xylem vessels, a flowing, low-nutrient habitat where biofilms could be adaptive. Ralstonia solanacearum forms biofilm in vitro, but it was not known if the pathogen benefits from biofilms during infection. Scanning electron microscopy revealed that during tomato infection, R.

Escaping Underground Nets: Extracellular DNases Degrade Plant Extracellular Traps and Contribute to Virulence of the Plant Pathogenic Bacterium Ralstonia solanacearum.

Plant root border cells have been recently recognized as an important physical defense against soil-borne pathogens. Root border cells produce an extracellular matrix of protein, polysaccharide and DNA that functions like animal neutrophil extracellular traps to immobilize pathogens. Exposing pea root border cells to the root-infecting bacterial wilt pathogen Ralstonia solanacearum triggered release of DNA-containing extracellular traps in a flagellin-dependent manner.

Root Border Cells and Their Role in Plant Defense.

Root border cells separate from plant root tips and disperse into the soil environment. In most species, each root tip can produce thousands of metabolically active cells daily, with specialized patterns of gene expression. Their function has been an enduring mystery.

Sensitive, Secure Detection of Race 3 Biovar 2 and Native U.S. Strains of Ralstonia solanacearum.

Detecting and correctly identifying Ralstonia solanacearum in infected plants is important because the race 3 biovar 2 (R3bv2) subgroup is a high-concern quarantine pathogen, while the related sequevar 7 group is endemic to the southeastern United States. Preventing accidental import of R3bv2 in geranium cuttings demands sensitive detection methods that are suitable for large-volume use both onshore and offshore. However, detection is complicated by frequent asymptomatic latent infections, uneven pathogen distribution within infected plants, pathogen viable-but-not-culturable state, and biosecurity laws that restrict transport of R3bv2 strains for diagnosis.

SERS spectroscopy and SERS imaging of Shewanella oneidensis using silver nanoparticles and nanowires.

Facile and reproducible SERS signals from Shewanella oneidensis were obtained utilizing silver nanoparticles (AgNPs) and silver nanowires (AgNWs). Additionally, SERS images identify the distribution of SERS hot-spots. One important observation is the synergistically enhanced SERS signal when AgNPs and AgNWs are used in conjunction, due to constructively enhanced electromagnetic field.