Proteomic analysis of grapevine resistance induced by Trichoderma harzianum T39 reveals specific defence pathways activated against downy mildew

Downy mildew, caused by the oomycete Plasmopara viticola, is one of the most serious of grapevine diseases. The beneficial microorganism Trichoderma harzianum T39 (T39) has previously been shown to induce plant-mediated resistance and to reduce the severity of downy mildew in susceptible grapevines. In order to better characterise the cellular processes associated with T39-induced resistance, proteomic and histochemical changes activated by T39 were analysed in grapevine before and one day after P. viticola inoculation. A comprehensive proteomic analysis of T39-induced resistance in grapevine was performed using an eight-plex iTRAQ protocol, resulting in the identification and quantification of a total of 800 proteins. Statistical analysis revealed 58 and 60 proteins to be significantly modulated by T39 treatment before and after P. viticola inoculation, respectively. In addition, 128 proteins were modulated by P. viticola inoculation in control plants. Most of the proteins directly modulated by T39 were involved in signal transduction, indicating activation of a complete microbial recognition machinery. T39-induced resistance was associated with rapid accumulation of reactive oxygen species and callose at infection sites, as well as modulation of the proteins involved in response to stress and redox balance, indicating an active defence response to downy mildew. On the other hand, proteins affected by P. viticola in control plants were mainly negatively modulated, which suggests that a compatible interaction may be taking place. As well as yielding data on the molecular processes responsible for T39-induced resistance, the high-throughput iTRAQ protocol allowed the improvement of protein sequences of the V. vinifera cv. Pinot Noir proteome.