Claus Martin

Drucker Turnip

Keywords:

teaching and research institutions in France or abroad, or from public or private research centers.

Turnip mosaic virus is a second virus that responds to the presence of aphid vectors and activates transmission

Claus

Turnip mosaic virus (TuMV) is transmitted by aphids and uses, like hundreds of other plant virus, the noncirculative mode, according to the molecular "helper" strategy. This indicates that the virus particles (virions) transmitted attach within seconds to the stylets and are transported to a new host plant. The connection between TuMV and the stylets is not direct; a transmission helper component (the viral protein HC-Pro) intervenes by creating the molecular link between virions and stylets. For cauliflower mosaic virus, another noncirculative virus using the helper strategy, but entirely unrelated to TuMV, the presence of vectors on the plant induces the passage from a state where the virus is not transmissible to a state where it becomes transmissible [START_REF] Bak | Virus factories of cauliflower mosaic virus are virion reservoirs that engage actively in vector transmission[END_REF][START_REF] Martinière | A virus responds instantly to the presence of the vector on the host and forms transmission morphs[END_REF]. The transmission of TuMV has been tested in order to determine if this virus also follows this strategy, called "Transmission Activation (TA)". The results of these tests showed that ROS (Reactive Oxygen Species) increases transmission, whereas calcium channel blockers inhibit it. Preliminary evidence suggests that oxidized forms of HC-Pro correlate with increased and reduced forms with decreased transmission. Taken together, the TuMV is a second example for TA.

  Turnip mosaic virus is a second virus that responds to the presence of aphid vectors and activates transmission Martin Drucker INRA, UMR BGPI, Montpellier, France


Melania Migliore

Loredana Canfora

Alessandro Florio

Flavia Pinzari

Maria Teresa Dell'abate

Anna Benedetti

Rosario Napoli

Maria Teresa

Unravelling the influence of plant cover and microbial diversity on ecosystem function of Melanic Andosols

à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.


Razik Benouaret
email: rbenouaret@yahoo.fr

Pascale Goupil
email: pascale.goupil@univ-bpclermont.fr

local tissue injury and PR expression in tobacco leaves

The valuable grape marc in crop protection

GME shows elicitor activity on suspension-cultured cells of tobacco GME mediates

Introduction

Conclusions

PDI potential

Plant protector

Activation of plant defense response against diseases provides a powerful management tool in phytoprotection. Many different substances could elicit plant defence, and there is an increasing demand for searching and identifying new ones. Currently, fast emerging natural phytosanitary products are known as plant defence inducers (PDIs).

Our group reports the elicitor activity of red grape marc extract (GME). GME is a wine by-product that contains a large proportion of polyphenols with anthocyanins. On application to tobacco leaves, it elicits a variety of defence reactions such as local injury, biochemical changes and systemic molecular response with upregulation of PR proteins. Additionally, we demonstrate that this extract induces resistance against Phytophthora parasitica on tobacco plants. • The BY-2 cells reacted to GME (0.25% and 0.125%) with a long-sustained pH rise in their growth medium.

• Cycloheximide and protease inhibitors suppressed partially GME-induced cell death.

• GME induced a significant protection of tobacco leaves towards the Oomycete P. parasitica. This level of protection is not shown in GME-treated NahG tobacco leaves.

GME induces resistance to Phytophthora parasitica infection of tobacco plants

• The marc extract of red grape cultivars reveals plant defence inducer properties. Treatment with grape marc extract efficiently induced hypersensitive reaction-like lesions and PR transcript accumulation.

• GME induced extracellular alkalinization of BY-2 cells characterized by long-sustained pH rise. The inhibitory effect of cycloheximide on GME-induced cell death indicates that GME triggered an active process requiring protein synthesis. Also, proteolytic events may take part in the mechanisms leading to cell death.

Results

This work was supported by grants from the FUI: Fonds Unique Interministériel-PHYTOMARC project

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  on tobacco leaves by water or 0.7% (v/v) GME infiltration. Leaves were observed under bright light field or UV light at 4 days post-infiltration. (ia) infiltrated area (sz) surrounding chlorotic zone. Bars 1 cm. Arrows point necrotic or fluorescent areas. Leaf protection induced by GME on tobacco plants expressing or not expressing the nahG gene. Leaves from 8-week-old tobacco plants treated with water or GME were inoculated with zoospores of P. parasitica at 0, 2 or 4 days post-treatment (dpt). The invaded areas were measured 3 days after inoculation. Each bar represents the standard error of four replicates from two different experiments. A replicate corresponds to eight inoculated areas on four leaves from two plants. Letters next to bars indicate statistically significant differences between samples, according to one-way ANOVA followed by LSD Significant test (p≤0.05). Expression of PR1, PR2, PR3 and PR5 in wild-type tobacco and NahG tobacco plants leaves infiltrated with 0.7% GME. The amount of transcript encoding genes was quantified by real-time PCR. Values are expressed relative to the control (water treatment) values. Two treated plants were pooled for each experiment, and the results are the means of duplicate experiments. Bars represent the mean values ± SE. Extracellular alkalinization in tobacco BY-2 suspension cells on addition of different concentrations of GME. The data are from representative experiments out of a total of five. Effects of cycloheximide and proteases inhibitors on GME-induced cell death. Chemicals were added 30 min prior to cell death measurement of BY-2 treated with water (Control) or 0.25% GME for 48 h. The final concentration of each chemical is 50 µM cycloheximide (+CHX), 0.2 µM aprotinin (+APR), 1 µM pepstatin (+PEPS), 1.5 µM E-64 (+E-64). Letters next to bars indicate statistically significant differences between samples, according to one-way ANOVA followed by LSD Significant test (p≤0.05).dpt • GME induced HR-like lesions into tobacco leaves. After infiltration, the surrounding leaf tissues spread out autofluorescent compounds.

  GME triggers high level of SAR gene expression in wild type tobacco plants compared to NahG plants. Moreover, the NahG plants display enhanced sensitivity to Phytophthora parasitica. These results suggest the potential role of SA in GME-induced defense responses and protection to pathogen.