Hydrophobic proteins secreted into the apoplast may contribute to resistance against Phytophthora infestans in potato.

During plant-pathogen interaction, oomycetes secrete effectors into the plant apoplast where they interact with host resistance proteins, which are accumulated after wounding or infection. Previous studies showed that the expression profile of pathogenesis related proteins is proportional to the resistance of different cultivars toward Phytophthora infestans infection. The aim of this work was to analyze the expression pattern of apoplastic hydrophobic proteins (AHPs), after 24 h of wounding or infection, in tubers from two potato cultivars with different resistance to P. infestans, Spunta (susceptible) and Innovator (resistant). Intercellular washing fluid (IWF) was extracted from tubers and chromatographed into a PepRPC™ HR5-5 column in FPLC eluted with a linear gradient of 75% acetonitrile. Then, AHPs were analyzed by SDS-PAGE and identified by MALDI-TOF-MS. Innovator cv. showed a higher basal AHP content compared to Spunta cv. In the latter, infection induced accumulation of patatins and protease inhibitors (PIs), whereas in Innovator cv. no changes in PIs accumulation were observed. In response to P. infestans infection, lipoxygenase, enolase, annexin p34 and glutarredoxin/cyclophilin were accumulated in both cultivars. These results suggest that the AHPs content may be related to the protection against the oomycete and with the degree of potato resistance to pathogens. Additionally, a considerable number of the proteins putatively identified lacked the signal peptide and, being SecretomeP positive, suggest unconventional protein secretion.

Cytoskeletal ultrastructure and lipid composition of I-Z-I fraction in muscle from pre- and post-spawned female hake (Merluccius hubbsi).

Myofibrils from pre- and post-spawned female hake were depleted of thin and thick filaments by KI-treatment and the cytoskeletal ultrastructure of the preparations was investigated by electron microscopy. Irrespective of the gonadal stage of the fish, transmission (TEM) and scanning (SEM) electron micrographs showed an extensive network of filaments connecting Z-structures, which appeared as two circular rings held together. Z-structures of KI-treated myofibrils from post-spawned hake were more compact than those from pre-spawned fish. This ultrastructural difference was absent when KI-treated myofibrils from hake in both gonadal conditions were prepared in the presence of a proteinase inhibitor cocktail (1 mM EDTA+1 mM PMSF+1 mM iodoacetic acid). The total lipid (TL) content of the I-Z-I fraction from fish in pre-spawned condition was about 3.7 mg/g I-Z-I and non-polar lipids (NPL) represent 86.5% of TL. TL and NPL contents of the I-Z-I fraction from post-spawned hake were about 50% and 78.2% lower than those obtained from this fraction in pre-spawning fish. No significant changes (p>0.05) were observed in phospholipids (PL) and acidic phospholipids (AP). No significant differences (p<0.01) were observed among the corresponding lipid fractions of I-Z-I purified from pre- and post-spawning fish in the presence of a protease inhibitor cocktail.