Apoptosis in etiolated wheat seedlings: 2. Effects of the antioxidant butylated hydroxytoluene and peroxides

Abstract

The antioxidant butylated hydroxytoluene (BHT, 50 mg/l, 2.27 × 10–4 M) was found to prevent the development of characteristic signs of senescence and apoptosis in the cells of etiolated wheat (Triticum aestivum L.) seedlings. In particular, BHT blocked the apoptotic and age-induced formation of specific cytoplasmic mitochondria-containing vesicles in the coleoptiles. In contrast, the oxidants (H2O2 and cumene hydroxyperoxide) accelerated apoptosis (DNA fragmentation) in the coleoptiles and induced it in the first leaves, while in the control leaves, there were no signs of apoptosis. Thus, the programmed developmental apoptosis is controlled by the reactive oxygen species (ROS), and anti- and prooxidants can actively affect this process. In the coleoptile, BHT induced substantial changes in the ultrastructure of all cell organelles (nucleus, mitochondria, plastids, Golgi apparatus, and endoplasmic reticulum). It also induced the formation of unusual membrane structures in the cytoplasm and impaired nucleus and cell divisions. As a result, giant multilobed nuclei and multinuclear cells appeared. The effects of the antioxidant were tissue-specific: BHT did not noticeably affect cell ultrastructure in the first leaf. In roots of etiolated seedlings, BHT stimulated unusual plastid differentiation that resulted in the formation of chloroplasts, which is a phenomenon abnormal for roots. The BHT effects on the plant are evidently related to its antioxidant properties. Indeed, its structural analog, 3,5-di-tert-butyltoluene, which does not exhibit antioxidant properties, was physiologically inert. The BHT-controlled ROS evidently triggered apoptosis and produced age-dependent structural rearrangements of the cytoplasm and the formation of specific mitochondria-containing vesicles, which actively synthesize mtDNA. ROS inactivation by BHT is evidently responsible for BHT-induced changes in the structure of all cell organelles. Therefore, we believe that ROS control cell division (including nucleus division and cell-wall formation) and affect the differentiation of plastids and Golgi apparatus. In such a way, ROS effectively control plant growth and development.