植物の病原菌感染応答に関する電子顕微鏡学的解析

Abstract

When plants come into contact with fungal pathogens and their disease chemical stressors such as toxins and elicitors, they exhibit a variety of complex cell responses against the disease stress. Some plants induce a series of resistant reactions to the stress, eventually resulting in survival by overcoming it, while some submit to fungal infection because of failure to establish defense reactions. Electron microscopy is one of a number of powerful techniques that can analyze cell functions with pathological significance by observing the responses of the stressed plant cells. This article describes the results of ultrastructural analysis on both the mode of action of Alternaria and Stemphylium host-specific toxins (HSTs) produced from some saprophytic pathogens in respective host cells to evaluate the pathological roles of HSTs. In addition, the aggressive roles of pathogen penetration pegs, lignin-induced resistant responses, and the apoptosis-like cell death mechanism by pathogen infection are also reported. Ultrastructural studies of plant diseases had been performed vigorously and extensively in the 1970s and 1980s in Japan, but they declined in number and in the 1990s they came to a standstill. This tendency is common in every field of natural science. Unfortunately, experts in electron microscopy with diverse and skillful techniques are now less common due to their gradual retirement from employment. The cytological posts have been insured by genome workers. The decline of electron microscopy is attributed to the difficulty of electron microscopy techniques and the rise of molecular biology. Molecular biology is excellent in analyzing the gene functions of pathogen-stressed host cells or differentiated pathogens during pathogenesis and the tech-