Changes in protease inhibitors hydrophobicity could be associated with

M. B. FERNANDEZ , M. R. PAGANO , G. R. DALEO, M. G. GUEVARA

Oregon, EEUU

Congreso; Annual Meeting of American Phytopathological Society (APS); 2009

The plant apoplast has a high content of proteases and protease inhibitors (PI), either with or without antimicrobial activity, which are important components of the response towards different stresses. However, the way by which PI interact with pathogen effectors is unknown. On the other hand, apoplastic hydrophobic proteins and peptides (AHPs) have been associated with plant defence response. We have analyzed if stress induced changes in the hydrophobicity of apoplastic PI (API), in two potato cultivars with different degree of resistance to P. infestans. Intercellular fluid was extracted from tubers (IFT) and chromatographed into a PepRPC™ HR 5-5 column in FPLC eluted with a linear gradient of 0 to 75% acetonitrile. Then, AHPs were analyzed by SDS-PAGE and identified by MS-MS and MALDI-TOF. In both cultivars, API hydrophobicity was increased. After 24 h of wounding or infection, Spunta cv (susceptible), showed that cysteine (19–23 KDa) and Kunitz-type PI were mostly hydrophobic. In Innovator cv (resistant) both treatments induced an increase in PI hydrophobicity; however this effect was higher after 24 h. of wounding. The results obtained here suggest that changes in protein hidrophobicity are neccesary to protect the tuber under biotic and abiotic stress, regardless of cultivar resistance degree. However, modifications in the exposure of hydrophobic sites could be related to changes in proteaseinhibitor interactions participating in the plant defence response.