Protéomique fonctionnelle de l’interaction Phytophthora infestans - Solanum tuberosum pendant la phase biotrophe de l’infection.

Proteomic analysis of Phytophthora infestans - Solanum tuberosum interaction during the biotrophic phase growth.

Context

Oomycetes such as members of the genus Phytophthora form a distinct group of fungal-like eukaryotic organisms that are related to brown algae and diatoms in the Stramenopiles. Oomycetes include several plant pathogen species among which Phytophthora infestans, the causal agent of late blight, is the most devastating one. Phytophthora infestans is thought to cause annual losses to potato production amounting to more than several billions dollars. The effective protection provided by pesticides can be compromised by adverse environmental conditions and the emergence of resistant pathogen strains. Furthermore, the impetus provided by the current emphasis on the protection of the environment and human health is stimulating the development of alternative strategies to the chemical control of late blight epidemics. These include natural resistance activators, fungicides of natural origin and biocontrol agents. A simplified view has suggested that both host and non-host resistance to P. infestans was associated with the gene-to-gene model. In this model signal molecules encoded by pathogen avirulence genes (Avr) interact directly with specific receptors encoded by host resistance genes (R) and lead to the activation of resistance mechanisms.

Objectives

Proteomics studies will be used to explore the global patterns of protein expression in the Phytophthora infestans/Solanum tuberosum pathosystem during the initial biotrophic phase of infection. Special attention will be paid to the switch from the biotrophic growth phase to necrotrophy.

Expected results

- improved understanding of the complex control of in planta growth; - insights into the biochemical pathways required for successful invasive growth. - insights into the molecular events that control the switch to necrotrophy. Understanding the molecular basis of plant disease sensitivity will enhance our ability to control and minimize pathogen-induced yield losses in agriculture.

Results obtained

In a preliminary step we characterized the metabolic plant response to infection by measuring chlorophyll fluorescence and oxygen evolution rates. Despite a significant reduction of the photosynthetic activity , the relationship of photosynthetic electron transport rates (ETR) to oxygen evolution was kept unchanged during biotrophic growth phase. Down-regulation of ETR was achieved by increased photochemical quenching. Based on these results, we formulate the following working hypothesis: during biotrophic growth phase an energy sink other than the photosynthetic carbon reduction and PCO cycles is activated to prevent over-reduction of the photosynthetic apparatus and photooxidatives damages to both host and pathogen components.