Proteomic Analysis of Phytophthora infestans Reveals the Importance of Cell Wall Proteins in Pathogenicity

Abstract

The oomycete Phytophthora infestans is the most harmful pathogen of potato. It causes the disease late blight, which generates increased yearly costs of up to one billion euro in the EU alone and is difficult to control. We have performed a large-scale quantitative proteomics study of six P. infestans life stages with the aim to identify proteins that change in abundance during development, with a focus on preinfectious life stages. Over 10 000 peptides from 2061 proteins were analyzed. We identified several abundance profiles of proteins that were up- or downregulated in different combinations of life stages. One of these profiles contained 59 proteins that were more abundant in germinated cysts and appressoria. A large majority of these proteins were not previously recognized as being appressorial proteins or involved in the infection process. Among those are proteins with putative roles in transport, amino acid metabolism, pathogenicity (including one RXLR effector) and cell wall structure modification. We analyzed the expression of the genes encoding nine of these proteins using RT-qPCR and found an increase in transcript levels during disease progression, in agreement with the hypothesis that these proteins are important in early infection. Among the nine proteins was a group involved in cell wall structure modification and adhesion, including three closely related, uncharacterized proteins encoded by PITG_01131, PITG_01132, and PITG_16135, here denoted Piacwp1–3. Transient silencing of these genes resulted in reduced severity of infection, indicating that these proteins are important for pathogenicity. Our results contribute to further insight into P. infestans biology, and indicate processes that might be relevant for the pathogen while preparing for host cell penetration and during infection. The mass spectrometry data have been deposited to ProteomeXchange via the PRIDE partner repository with the data set identifier PXD002446. The oomycete Phytophthora infestans is the most harmful pathogen of potato. It causes the disease late blight, which generates increased yearly costs of up to one billion euro in the EU alone and is difficult to control. We have performed a large-scale quantitative proteomics study of six P. infestans life stages with the aim to identify proteins that change in abundance during development, with a focus on preinfectious life stages. Over 10 000 peptides from 2061 proteins were analyzed. We identified several abundance profiles of proteins that were up- or downregulated in different combinations of life stages. One of these profiles contained 59 proteins that were more abundant in germinated cysts and appressoria. A large majority of these proteins were not previously recognized as being appressorial proteins or involved in the infection process. Among those are proteins with putative roles in transport, amino acid metabolism, pathogenicity (including one RXLR effector) and cell wall structure modification. We analyzed the expression of the genes encoding nine of these proteins using RT-qPCR and found an increase in transcript levels during disease progression, in agreement with the hypothesis that these proteins are important in early infection. Among the nine proteins was a group involved in cell wall structure modification and adhesion, including three closely related, uncharacterized proteins encoded by PITG_01131, PITG_01132, and PITG_16135, here denoted Piacwp1–3. Transient silencing of these genes resulted in reduced severity of infection, indicating that these proteins are important for pathogenicity. Our results contribute to further insight into P. infestans biology, and indicate processes that might be relevant for the pathogen while preparing for host cell penetration and during infection. The mass spectrometry data have been deposited to ProteomeXchange via the PRIDE partner repository with the data set identifier PXD002446. Phytophthora infestans is a devastating oomycete plant pathogen that causes the disease late blight on potato and several related plants. It originated in South or Central America and reached Europe during the middle of the nineteenth century. The first described major outbreak culminated in the Great Irish Famine of 1845–1852 (1.Agrios G.N. Plant pathology. Elsevier Academic Press, Amsterdam2004Google Scholar). Since then, it has been the most damaging pathogen for potato growers in Europe and North America. The costs of reduction in yield due to late blight and of measures to control the disease have been estimated to more than one billion euro in the EU alone (2.Haverkort A. Boonekamp P. Hutten R. Jacobsen E. Lotz L. Kessel G. Visser R. van der Vossen E. Societal costs of late blight in potato and prospects of durable resistance through cisgenic modification.Potato Res. 2008; 51: 47-57Crossref Scholar). for late blight control on of a of potato with durable resistance has not been P. infestans has the to change of and by potato Phytophthora infestans to the a in the that with the and a that is from and The of life from a Scholar). 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We quantitative proteomics to identify proteins in P. infestans that are important in life stages. several proteins involved in cell wall of these proteins are to a in early infection the were abundant during on and in the early stages of infection. one group of proteins to be important for infection, being involved in of germinated cysts and appressoria. Our data further insight into the and processes the of infection in the oomycete P. a devastating pathogen that causes in potato and The increased of the of and the of it important to the infection to for the of that proteomics with of the identified proteins is to the of