Identification of avocado (Persea americana) root proteins induced by infection with the oomycete Phytophthora cinnamomi using a proteomic approach

Avocado root rot, caused by Phytophthora cinnamomi, is the most important disease that limits avocado production. A proteomic approach was employed to identify proteins that are upregulated by infection with P. cinnamomi. Different proteins were shown to be differentially expressed after challenge with the pathogen by two‐dimensional (2‐D) gel electrophoresis. A densitometric evaluation of protein expression indicated differential regulation during the time‐course analyzed. Some proteins induced in response to the infection were identified by standard peptide mass fingerprinting using matrix‐assisted laser desorption/ionization‐time of flight‐mass spectrometry and sequencing by MALDI LIFT‐TOF/TOF tandem mass spectrometry. Of the 400 protein spots detected on 2‐D gels, 21 seemed to change in abundance by 3 hours after infection. Sixteen proteins were upregulated, 5 of these were only detected in infected roots and 11 showed an increased abundance. Among the differentially expressed proteins identified are homologs to isoflavone reductase, glutathione S‐transferase, several abscisic acid stress‐ripening proteins, cinnamyl alcohol dehydrogenase, cinnamoyl‐CoA reductase, cysteine synthase and quinone reductase. A 17.3‐kDa small heat‐shock protein and a glycine‐rich RNA‐binding protein were identified as downregulated. Our group is the first to report on gene induction in response to oomycete infection in roots from avocado, using proteomic techniques.