Proteomic approch: Identification of Medicago truncatula proteins induced in roots after infection with the pathogenic oomycete Aphanomyces euteiches

The legume root rot disease caused by the oomycete pathogen Aphanomyces euteiches is one major yieldreducing factor in legume crop production. A comparative proteomic approach was carried out in order toidentify proteins of the model legume Medicago truncatula which are regulated after an infection withA. euteiches. Several proteins were identified by two dimensional gel electrophoresis to be differentiallyexpressed after pathogen challenge. Densitometric evaluation of expression values showed different regulationduring the time-course analysed. Proteins regulated during the infection were identified by matrixassisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS). Among thedifferentially expressed proteins, two encoded putative cell wall proteins and two were designated as smallheat shock proteins. Furthermore, an isoform of the chalcone-O-methyltransferase was found to be increasedin infected roots. The majority of induced proteins belonged to the family of class 10 of pathogenesisrelated proteins (PR10). Previously, various PR10-like proteins have been shown to be regulated bygeneral stress or abscisic acid (ABA). Therefore, these proteins were further investigated concerning theirregulation in response to drought stress and exogenous ABA-application. Complex regulation patternswere identified: three of the A. euteiches-induced PR10-like proteins were also induced by exogenous ABAbutnone of them is induced after drought stress. In contrast, three of these proteins are down-regulated bydrought stress. Hence, the strong expression of different PR10-family members and their regulation profilesindicates that this set of proteins plays a major role during root adaptations to various stress conditions.