Effects of Iodoacetamide on the Fine Structure of Azuki Bean Protoplast and its Fusion Product

Abstract

Effects of iodoacetamide (IOA) on azuki bean protoplasts and their fusion products were examined with emphasis on thc fine structure. Protoplasts were isolated enzymatically from cell suspension culture 4∼6 days after subculture. Protoplasts were then treated with IOA before culturing. Protoplasts were also fused with untreated protoplasts of mung bean leaf. Untreated and IOA-treated protoplasts of azuki bean and their fusion products were treated for viability, cell wall formation test and electron microscopy. Viability of IOA-treated protoplasts was extremely reduced after 3 days in culture. Cell wall regeneration was not detected. Furthermore, no cell division was observed in these protoplasts. Ultrastructurally, IOA-treated protoplasts performed apparent peculiarity with an overformation of rough endoplasmic reticulum (rER) and formation of circular Golgi complexes. This was followed by accumulation of lipid bodies within the cytoplasm. After 3 days in culture, protoplasts exhibited abundant accumulation of electron dense particles. Some of them showed collapse as indicated by shrinkage of their organelles and cytoplasm. In contrast to these protoplasts, untreated protoplasts had a performance as meristematic cell and cell division firstly observed after 3 days in culture. The effects of IOA, such as overformation of rER and circular Golgi bodies, were not found in the fusion product with untreated protoplasts. Otherwise, swelling of thylakoid in chloroplast was detected. The heterokaryons were able to maintain their survival for several days.