Abstract
We investigated whether α-amylaseI-1 is involved in the degradation of starch in rice leaf chloroplasts. We generated a series of α-amylaseI-1 co-suppressed and overexpressed transgenic rice. In the co-suppression lines, the seed germination and seedling growth delayed. However, the retardation effects for growth were overcome by supplementation of sugar. Interestingly, significant increase of starch accumulation in the young leaf tissues was observed under sugar-supplemented condition. In contrast, starch contents in leaves were reduced in the overexpression lines. In immunocytochmical analysis with specific anti-α-amylase I-1 antiserum, immuno-gold particles deposited at chloroplasts and extracellular space in young leaf cells. In addition, mature protein species of α-amylaseI-1 bearing oligosaccharide side chain were detected in the isolated chloroplasts. We further examined expression and targeting of α-amylaseI-1 fused with GFP in re-differentiated green cells, indicating that the fluorescence of expressed fusion protein co-localized with the chlorophyll autofluorescence in the transgenic cells.
