Separation and characterization of proteins from green and etiolated shoots of rice (Oryza sativa L.): Towards a rice proteome

Proteins extracted from green and etiolated shoots of rice were separated b y two-dimensional polyacrylamide gel electrophoresis and relative molecular weights and isoelectric points were determined. The separated proteins wer e electroblotted onto a polyvinylidene difluoride membrane and 85 proteins were analyzed by a gas-phase protein sequencer. The N-terminal amino acid s equences of 21 out of 85 proteins were determined in this manner. N-termina l regions of the remaining proteins could not be sequenced. The internal am ino acid sequences of proteins were determined by sequence analysis of pept ides obtained by the Cleveland peptide mapping method and compared with tho se of known plant and animal protein sequences to understand the nature of the proteins. Green shoots revealed the presence of photosynthetic proteins as expected; however, as etiolated shoots were not photosynthetic, only pr ecursors of the photosynthetic proteins were identified. Interestingly, the presence of L-ascorbate peroxidase only in etiolated shoots suggests a cel lular protectant function for this antioxidant enzyme in the etiolating sho ots. Using this experimental approach, we could identify the major proteins involved in growth regulation in photosynthetic green shoots as well as in etiolating rice seedlings.