Differentially Expressed Wound-response-related Proteins from a Major Agarwood-producing Tree, Aquilaria malaccensis Lam. Identified via 2-D Electrophoresis

Background: Wounding is the major trigger factor for agarwood formation in Aquilaria malaccensis. To date, the mechanism of agarwood formation in Aquilaria has been extensively explored through anatomy and genomics approaches; however, at the protein level, it is yet to be reported. Objective: A comparative proteomics analysis was carried out to identify proteins responsive to wounding in A. malaccensis, using two-dimensional gel electrophoresis (2-DE) coupled with Matrix- Assisted Laser Desorption/Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS). Method: Proteins were extracted from A. malaccensis tree stems at 0, 6, 12, and 24 h after wounding and separated by 2-DE, sequenced using MALDI-TOF MS and identified through UniProt/Swiss-Prot protein database. Results: Changes in differentially displayed proteins were observed. A total of 15 protein spots were identified reproducible under 2-DE, of which only two protein spots showed differences in expression affected by the wounding treatment in a time-dependent experiment. They were predicted as Malate Synthase (MS) and the reduced Nicotinamide Adenine Dinucleotide Phosphate (NADPH) quinone oxidoreductase subunit 2 B. Both proteins were directly and indirectly related to wounding treatments in plants and may be related to agarwood formation mechanism. Conclusion: As Aquilaria proteome is not available to date, this first report on differential protein expression in response to wounding could serve as a useful information towards understanding agarwood biosynthesis at the protein level.