Effect of the antioxidant ionol (BHT) on growth and development of etiolated wheat seedlings: Control of apoptosis, cell division, organelle ultrastructure, and plastid differentiation

Ionol (BHT), a compound having antioxidant activity, at concentrations in t he range 1-50 mg/liter (0.45-10(-5)-2.27-10(-4) M), inhibits growth of etio lated wheat seedlings, changes the morphology of their organs, prolongs the coleoptile life span, and prevents the appearance of specific features of aging and apoptosis in plants. In particular, BHT prevents the age-dependen t decrease in total DNA content, apoptotic internucleosomal fragmentation o f nuclear DNA, appearance in the cell vacuole of specific vesicles with act ive mitochondria intensively producing mtDNA, and fort-nation of heavy mito chondrial DNA (rho = 1.718 g/cm(3)) in coleoptiles of etiolated wheat seedl ings. BHT induces large structural changes in the organization of all cellu lar organelles (nucleus, mitochondria, plastids, Golgi apparatus, endocytop lasmic reticulum) and the formation of new unusual membrane structures in t he cytoplasm. BHT distorts the division of nuclei and cells, and this resul ts in the appearance of multi-bladed polyploid nuclei, and multinuclear cel ls. In roots of etiolated wheat seedlings, BHT induces intensive, synthesis of pigments, presumably carotenoids, and the differentiation of plastids w ith formation of chloro- or chromoplasts. The observed multiple effects of BHT are due to its antioxidative properties (the structural BHT analog 3,5- di-tert-butyltoluene is physiologically inert; it has no effect similar to that of BHT). Therefore, the reactive oxygen species (ROS) controlled by BH T seem to trigger apoptosis and the structural reorganization of the cytopl asm in the apoptotic cell with formation of specific vacuolar vesicles that contain active mitochondria intensively producing mtDNA. Thus, the inactiv ation of ROS by BHT may be responsible for the observed changes in the stru cture of all the mentioned cellular organelles. This corresponds to the ide a that ROS control apoptosis and mitosis including formation of cell wall, and they are powerful secondary messengers that regulate differentiation of plastids and the Golgi apparatus in plants.