PpCRN7 and PpCRN20 of phythophthora parasitica regulate plant cell death leading to enhancement of host susceptibility

Phytophthora species secrete cytoplasmic effectors from a family named Crinkler (CRN), which are characterised by the presence of conserved specific domains in the N- and C-terminal regions. P. parasitica causes disease in a wide range of host plants, however the role of CRN effectors in these interactions remains unclear. Here, we aimed to: (i) identify candidate CRN encoding genes in P. parasitica genomes; (ii) evaluate the transcriptional expression of PpCRN (Phytophthora parasitica Crinkler candidate) during the P. parasitica interaction with Citrus sunki (high susceptible) and Poncirus trifoliata (resistant); and (iii) functionally characterize two PpCRNs in the model plant Nicotiana benthamiana. Results Our in silico analyses identified 80 putative PpCRN effectors in the genome of P. parasitica isolate 'IAC 01/95.1'. Transcriptional analysis revealed differential gene expression of 20 PpCRN candidates during the interaction with the susceptible Citrus sunki and the resistant Poncirus trifoliata. We have also found that P. parasitica is able to recognize different citrus hosts and accordingly modulates PpCRNs expression. Additionally, two PpCRN effectors, namely PpCRN7 and PpCRN20, were further characterized via transient gene expression in N. benthamiana leaves. The elicitin INF-1-induced Hypersensitivity Response (HR) was increased by an additive effect driven by PpCRN7 expression, whereas PpCRN20 expression suppressed HR response in N. benthamiana leaves. Despite contrasting functions related to HR, both effectors increased the susceptibility of plants to P. parasitica. Conclusions PpCRN7 and PpCRN20 have the ability to increase P. parasitica pathogenicity and may play important roles at different stages of infection. These PpCRN-associated mechanisms are now targets of biotechnological studies aiming to break pathogen's virulence and to promote plant resistance19CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ445390/2014–0; 465440/2014–

Phytophthora nicotianae diseases worldwide: new knowledge of a long-recognised pathogen

Phytophthora nicotianae was first isolated from tobacco at the end of the 19th century. This organism is now considered as one of the most devastating oomycete plant pathogens, with a recognized host range of more than 255 species over five continents and a wide diversity of climates. The economic losses caused by P. nicotianae are difficult to estimate, because of the diversity of its hosts and ecological niches. For these reasons, this pathogen represents a continuous challenge to plant disease management programmes, which frequently rely solely on the use of chemicals. Phytophthora nicotianae is better adapted than its competitors to abiotic stresses, especially to climate warming. As a result, its importance is increasing. This review illustrates, with some examples, how P. nicotianae currently impacts plant economies worldwide, and how it may constitute more severe threats to agriculture and natural ecosystems in the context of global climate change

The Top 10 oomycete pathogens in molecular plant pathology

Oomycetes form a deep lineage of eukaryotic organisms that includes a large number of plant pathogens which threaten natural and managed ecosystems. We undertook a survey to query the community for their ranking of plant-pathogenic oomycete species based on scientific and economic importance. In total, we received 263 votes from 62 scientists in 15 countries for a total of 33 species. The Top 10 species and their ranking are: (1) Phytophthora infestans; (2, tied) Hyaloperonospora arabidopsidis; (2, tied) Phytophthora ramorum; (4) Phytophthora sojae; (5) Phytophthora capsici; (6) Plasmopara viticola; (7) Phytophthora cinnamomi; (8, tied) Phytophthora parasitica; (8, tied) Pythium ultimum; and (10) Albugo candida. This article provides an introduction to these 10 taxa and a snapshot of current research. We hope that the list will serve as a benchmark for future trends in oomycete research.Keywords: microbiology, diversity, genomics, oomycetes plant patholog

Effect of phosphite treatment and <i>P. plurivora</i> infection on plant mortality over time.

<p>Treatments: Con (black square): not phosphite treated and not inoculated control plants; Phi (green square): plants sprayed with phosphite (0.5%) on leaves until run off; Plu (red circle): roots infected with <i>P. plurivora</i>; Phi-Plu (blue triangle): plants sprayed with phosphite (0.5%) on leaves until run off four days prior to infection with <i>P. plurivora</i>. n = 6 plants per treatment. The experiment was repeated three times showing similar results. dpi: days post inoculation.</p

Concentrations of phosphite and <i>P. plurivora</i> DNA along time.

<p>(a) Phosphite concentrations of root tissue. (b) qPCR analysis of <i>P. plurivora</i> DNA along time (ng/gDW). Red bars: Plants infected with <i>P. plurivora</i>; blue bars: Plants infected with <i>P. plurivora</i> and treated with phosphite (0.5%). Green bars: Plants treated with Phi. n = 6 plants per treatment. The experiments were repeated 3 times showing similar results. Dpi: days post inoculation. Different letters at the same time points show statistical differences (P≤0.05), N.S. =  Not-significant.</p

Effect of phosphite treatment and <i>P. plurivora</i> infection on the expression of defense-related genes.

<p>Absolute gene expression for PR1, PR2, PRP and WRKY (SA signaling pathway) as well as for PR3 and ACO (JA/ET signaling pathway) of beech saplings for all treatments. Purple and yellow bars represent control plants at time zero and after six days. Black and green bars represent phosphite treated plants at time zero and after six days. Blue bars represent infected plants at 6 dpi. Red bars represent phosphite-treated and infected plants at time 6 dpi. Asterisks show level of significance (P≤0.05*; P≤0.01**; P≤0.001***); N.S. Not-significant; n = 4. The experiment was repeated three times showing similar results.</p

Effect of phosphite on <i>in vitro</i> growth and zoospore production of <i>P. plurivora</i>.

<p>(a) Inhibition of <i>P. plurivora</i> mycelial growth using different phosphite concentrations. (b) <i>P. plurivora</i> cultures in Petri dishes illustrating the inhibition of mycelial radial growth with increasing phosphite concentrations. The mycelial colonies were six days old. (c) Inhibition of <i>P. plurivora</i> zoospore production at different phosphite concentrations. EC₅₀ shows the concentration that inhibits growth or zoospore production to 50%. Trend-lines were fitted using a logarithmic function. These assays were repeated three times showing similar results. n = 5 for each assay.</p

Effect of phosphite treatment on <i>P. plurivora</i> colonization of roots.

<p>Confocal laser scanning microscopy images of cross-sections of beech sapling roots infected with <i>P. plurivora</i> and either treated or not treated with phosphite after 2, 4 and 10 dpi (A, B, C). Beech sapling roots infected with <i>P. plurivora</i> and treated with phosphite (0.5%) after 2, 4 and 10 dpi (D, E, F). (Co) cortex, (CC) central cylinder, White bars represent 50 µm.</p

Effect of phosphite treatment and <i>P. plurivora</i> infection on net CO₂ assimilation rates (µmol CO₂ m⁻²s⁻¹) (a) and water uptake (b) over ten days.

<p>Water uptake was calculated as percent of g/cm² leaf surface of four months-old beech saplings. Treatments: Control: not infected and not phosphite treated plants; Phi: phosphite treatment; Plu: roots inoculated with zoospores of <i>P. plurivora</i>; Phi-Plu: foliar application of 0.5% phosphite on plants prior to inoculation with zoospores of <i>P. plurivora</i>. The experiment was repeated three times showing similar results. N = 6 plants per treatment. dpi- days post inoculation. Different letters at the same time points show statistical differences (P≤0.05), N.S. =  Not-significant.</p