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Why are Phytophthora and Other Oomycota not True Fungi?

Outlooks on Pest Management 10/2006; 17(5). DOI: 10.1564/17oct08
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    ABSTRACT: During pathogenic interactions, both the host and pathogen are exposed to conditions that induce programmed cell death (PCD). Certain aspects of PCD have been recently examined in eukaryotic microbes, but not in oomycetes. Here, we identified conserved TatD proteins in Phytophthora sojae; the proteins are key components of DNA degradation in apoptosis. We selected PsTatD4 for further investigation because the enzyme is unique to the oomycete branch of the phylogenetic tree. The purified protein exhibited DNase activity in vitro. Its expression was upregulated in sporangia and later infective stages, but downregulated in cysts and during early infection. Functional analysis revealed that the gene was required for sporulation and zoospore production, and the expression levels were associated with the numbers of H2O2-induced TUNEL-positive cells. Furthermore, overexpression of PsTatD4 gene reduced the virulence in a susceptible soybean cultivar. Together, these data suggest that apoptosis may play different roles in the early and late infective stages of P. sojae, and that PsTatD4 is a key regulator of infection. The association of PsTatD4 and apoptosis will lay a fundament to understand the basic biology of apoptosis and its roles in P. sojae disease cycle.
    Molecular Plant-Microbe Interactions 06/2014; 27(10). DOI:10.1094/MPMI-05-14-0153-R · 4.46 Impact Factor
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    ABSTRACT: After being accidentally introduced from the USA at the end of the 19th century, downy mildew caused by Plasmopara viticola (Berk. et Curt.) Berlese et De Toni became one of the most damaging diseases affecting Vitis vinifera in Europe. Downy mildew causes both direct and indirect losses and can lead to severe reduction of yield. Our understanding of the life cycle and epidemiology of P. viticola has been recently altered by molecular studies that revealed that the overwintering inoculum (i.e., the oospores) does more than initiate disease, as was previously thought. A mechanistic model was developed for predicting the entire chain of processes leading to primary infections, and this primary infection model was linked to other models of secondary infection cycles. The model for primary infections defines the length of the primary inoculum season and a seasonal oospore dose consisting of several cohorts of oospores that progressively mature. The model was evaluated by means of Bayesian analysis in both Italy and eastern Canada, and showed high sensitivity, specificity, and accuracy both for potted plants and vineyards. Fungicide applications are necessary to control downy mildew because preventive agronomic practices are not very effective, including host resistance. The use of warning systems based on weather-driven models leads to a reduction in the use and cost of chemicals and a reduction in their environmental impact.
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