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Fusarium verticillioides, a well-known fungal pathogen that causes severe disease in maize and contaminates the grains with fumonisin B1 (FB1) mycotoxin, affects the yield and quality of maize worldwide. The intrinsic roles of peroxisome targeting signal (PTS)–containing proteins in phytopathogens remain elusive. We therefore explored the regulatory role and other biological functions of the components of PTS2 receptor complex, FvPex7 and FvPex20, in F. verticillioides. We found that FvPex7 directly interacts with the carboxyl terminus of FvPex20 in F. verticillioides. PTS2-containing proteins are recognized and bound by the FvPex7 receptor or the FvPex7-Pex20 receptor complex in the cytoplasm, but the peroxisome localization of the PTS2-Pex7-Pex20 complex is only determined by Pex20 in F. verticillioides. However, we observed that some putative PTS2 proteins that interact with Pex7 are not transported into the peroxisomes, but a PTS1 protein that interacts with Pex5 was detected in the peroxisomes. Furthermore, ΔFvpex7pex20 as well as ΔFvpex7pex5 double mutants exhibited reduced pathogenicity and FB1 biosynthesis, along with defects in conidiation. The PTS2 receptor complex mutants (ΔFvpex7pex20) grew slowly on minimal media and showed reduced sensitivity to cell wall and cell membrane stress-inducing agents compared to the wild type. Taken together, we conclude that the PTS2 receptor complex mediates peroxisome matrix proteins import and contributes to pathogenicity and FB1 biosynthesis in F. verticillioides. Key points: • FvPex7 directly interacts with FvPex20 in F. verticillioides. • vThe PTS2 receptor complex is essential for the importation of PTS2-containing matrix protein into peroxisomes in F. verticillioides. • Fvpex7/pex20 is involved in pathogenicity and FB1 biosynthesis in F. verticillioides. [ABSTRACT FROM AUTHOR]

Metacaspase is discovered gene family with distant caspase homologs in protozoa, fungi, and plants. The Arabidopsis genome has nine metacaspase genes. Based on the presence or absence of an N-terminal domain, they can be divided into two types of metacaspase genes: type I ( AtMC1 to 3) and type II ( AtMC4 to 9). To examine the expression patterns of the Arabidopsis metacaspase gene family, we measured the levels of expression of the metacaspase genes in various tissues and during biotic stresses by quantitative reverse transcription-polymerase chain reaction. As expected, the nine AtMC genes were expressed differently among tissues and during diverse stress conditions. In addition, to address the spatial expression of AtMC genes, their expression patterns using the promoter region of AtMCs (0.85 kb to 2.55 kb) were examined by the GUS reporter system. By observing GUS activity in transgenic plants containing nine AtMCpro::GUS constructs, we found that expression of these nine AtMC genes was regulated developmentally and spatially. We also observed that AtMC::green fluorescent fusion proteins were mainly localized in the nucleus using the Arabidopsis protoplast transient assay. In summary, our data suggest that AtMCs gene family be involved in various defense responses during biotic stresses. [ABSTRACT FROM AUTHOR]

In order to study the formation of fumonisin artefacts and the binding of fumonisins to matrix components (e.g. starch and protein) in thermal treated food, model experiments were performed by heating fumonisin FB1 with amino acid derivatives (protein model) and methyl-a-D-glucopyranoside (starch model). The reaction products were analysed by highperformance liquid chromatography-electrospray ionisationtandem mass spectrometry (HPLC-MS/MS). Using MS/MS experiments the formed reaction products were characterized as conjugates between fumonisin B1 and the used substrates. The reaction product between fumonisin B1 and methyl-α-D-glucopyranoside was purified and identified by nuclear magnetic resonance (NMR) spectroscopy as the diester of fumonisin B1 and methyl-α-D-glucopyranoside. These studies indicate that fumonisins can bind to matrix components via their TCA side chains. [ABSTRACT FROM AUTHOR]