Sucrose-Controlled Transport and Turnover of α-Amylase in Rice (Oryza sativa L.) Cells

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We studied the sucrose-controlled intracellular transport and turnover of α-amylase molecules in suspensioncultured cells of rice (Oryza sativa L.) employing pulse labeling techniques with [^<35>S] amino acids. The secretion of two classes of α-amylase isoforms, α-amylase I-1 (encoded by RAmy1A) and II-4 (encoded by RAmy3D) was differentially controlled by sucrose. In rice cells labeled with [^<35>S] amino acids under different sucrose-supplemented conditions, sucrose preferentially prevented the extracellular liberation of [^<35>S]-labeled α-amylase II-4 molecules from rice cells at around 2 mM, whereas the de novo protein synthesis still occurred at this concentration. Pulse-chase experiments showed that sucrose regulates the intracellular transport of [^<35>S]α-amylase II-4 molecules and stimulates the protein turnover. However, cycloheximide, a protein synthesis inhibitor. was induced the extracellular liberation and reduced the turnover of [^<35>S]α-amylase II-4 molecules in the presence of sucrose. These results strongly suggested that newly synthesized sucrose-induced proteins are involved in the posttranslational regulation on sucrose-controlled α-amylase secretion in rice cells.
日本植物生理学会の論文