Fengycin Produced by Bacillus amyloliquefaciens FZB42 Inhibits Fusarium graminearum Growth and Mycotoxins Biosynthesis.

Fusarium graminearum is a notorious pathogen that causes Fusarium head blight (FHB) in cereal crops. It produces secondary metabolites, such as deoxynivalenol, diminishing grain quality and leading to lesser crop yield. Many strategies have been developed to combat this pathogenic fungus; however, considering the lack of resistant cultivars and likelihood of environmental hazards upon using chemical pesticides, efforts have shifted toward the biocontrol of plant diseases, which is a sustainable and eco-friendly approach. Fengycin, derived from Bacillus amyloliquefaciens FZB42, was purified from the crude extract by HPLC and further analyzed by MALDI-TOF-MS. Its application resulted in structural deformations in fungal hyphae, as observed via scanning electron microscopy. In planta experiment revealed the ability of fengycin to suppress F. graminearum growth and highlighted its capacity to combat disease incidence. Fengycin significantly suppressed F. graminearum, and also reduced the deoxynivalenol (DON), 3-acetyldeoxynivalenol (3-ADON), 15-acetyldeoxynivalenol (15-ADON), and zearalenone (ZEN) production in infected grains. To conclude, we report that fengycin produced by B. amyloliquefaciens FZB42 has potential as a biocontrol agent against F. graminearum and can also inhibit the mycotoxins produced by this fungus.

Rice aquaporin PIP1;3 and harpin Hpa1 of bacterial blight pathogen cooperate in a type III effector translocation.

Varieties of Gram-negative bacterial pathogens infect their eukaryotic hosts by deploying the type III translocon to deliver effector proteins into the cytosol of eukaryotic cells in which effectors execute their pathological functions. The translocon is hypothetically assembled by bacterial translocators in association with the assumed receptors situated on eukaryotic plasma membranes. This hypothesis is partially verified in the present study with genetic, biochemical, and pathological evidence for the role of a rice aquaporin, plasma membrane intrinsic protein PIP1;3, in the cytosolic import of the transcription activator-like effector PthXo1 from the bacterial blight pathogen. PIP1;3 interacts with the bacterial translocator Hpa1 at rice plasma membranes to control PthXo1 translocation from cells of a well-characterized strain of the bacterial blight pathogen into the cytosol of cells of a susceptible rice variety. An extracellular loop sequence of PIP1;3 and the α-helix motif of Hpa1 determine both the molecular interaction and its consequences with respect to the effector translocation and the bacterial virulence on the susceptible rice variety. Overall, these results provide multiple experimental avenues to support the hypothesis that interactions between bacterial translocators and their interactors at the target membrane are essential for bacterial effector translocation.