Characterisation of proteins in the storage organs of Curcuma alismatifolia Gagnep.

Abstract

SummaryCurcuma alismatifolia rhizomes are exported to world markets for ornamental use. Rhizome size and the number of storage roots affected shoot sprouting, plant growth, and inflorescence yield and quality, indicating an important role for storage food reserves such as the carbohydrates and proteins in these organs. An understanding of the proteins used for growth and development in rhizomes and in storage roots is lacking, so changes in the storage proteins in these organs were investigated at the planting stage, the sprouting stage, the second-leaf stage, the flowering stage, and the dormancy stage. The protein concentrations in both these organs decreased rapidly until the flowering stage in order to support the initial growth of roots and shoots. The intensity of Coomassie Brilliant Blue staining of tissues was stronger in rhizomes than in storage roots. Protein staining was present in the cytosol and in the cell walls in rhizomes, and was intense in small particle-like protein bodies in the cytosol. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) profiles showed that peptides of 10.6 kDa and 12.0 kDa were the two major soluble proteins in rhizomes and were different from the proteins in storage roots.The 10.6 kDa and 12.0 kDa bands contained five peptides and one peptide, respectively, when separated by 2D-PAGE. The amino acid sequences of these six peptides were not homologous to any known proteins using BLASTP or FASTA analysis. The N-terminal amino acid sequences of these two polypeptides did not start with methionine, indicating that they had undergone posttranslational modification. Knowledge of the major storage proteins in the rhizomes and storage roots of C. alismatifolia may provide information to improve N-fertilisation.