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Background: Sago palm (Metroxylon sagu) is a versatile crop and has been hailed as the next viable commodity in Sarawak, Malaysia. Sago palm can thrive in the harsh swampy peat, from low flooded areas to uplands and in acidic to neutral soils. Sago palm has been neglected and unfortunately, very little is known about the sago palm proteome. This study aimed to determine the best protein extraction method of Metroxylon sagu for the two-dimensional gel electrophoresis (2-DE) and its comparative analysis. Results: To perform good proteome research, the most critical step is to establish a method that gives the best quality of extracted total proteins. Five different protein extraction protocols: polyethylene glycol (PEG) fractionation method, phenol extraction method, TCA–acetone method, the combination of phenol and TCA–acetone extraction method and imidazole method were compared to develop an optimized protein extraction method for two-dimensional gel electrophoresis analysis of Metroxylon sagu. The PEG fractionation method was found to give the most reproducible gels with the highest number of spots and highest protein concentration followed by phenol extraction method. The lowest number of spots was observed in the imidazole method. The PEG fractionation method provides improved resolution and reproducibility of 2-DE and reduces the time required to analyze samples. Partitioning Rubisco by polyethylene glycol (PEG) fractionation provides clearer detection of low abundance protein. Hence, the results from this study propose PEG fractionation as the effective protein extraction method for 2-DE proteomic studies of Metroxylon sagu. Conclusion: In this study, the PEG fractionation method is considered as the best extraction method for 2-DE proteomic studies of Metroxylon sagu in terms of yield, gel quality, spot numbers, and quantities of proteins. [ABSTRACT FROM AUTHOR]

Metroxylon sagu Rottb. or locally known as sago palm is a tropical starch crop grown for starch production in commercial plantations in Malaysia, especially in Sarawak, East Malaysia. This plant species accumulate the highest amount of edible starch compared to other starch-producing crops. However, the non-trunking phenomenon has been observed to be one of the major issues restricting the yield of sago palm starch. In this study, proteomics approach was utilised to discover differences between trunking and non-trunking proteomes in sago palm leaf tissues. Total protein from 16 years old trunking and non-trunking sago palm leaves from deep peat area were extracted with PEG fractionation extraction method and subjected to two-dimensional gel electrophoresis (2D PAGE). Differential protein spots were subjected to MALDI-ToF/ToF MS/MS. Proteomic analysis has identified 34 differentially expressed proteins between trunking and non-trunking sago samples. From these protein spots, all 19 proteins representing different enzymes and proteins have significantly increased in abundance in non-trunking sago plant when subjected to mass spectrometry. The identified proteins mostly function in metabolic pathways including photosynthesis, tricarboxylic acid cycle, glycolysis, carbon utilization and oxidative stress. The current study indicated that the several proteins identified through differentially expressed proteome contributed to physical differences in trunking and non-trunking sago palm. [ABSTRACT FROM AUTHOR]