KOBAYASHI Issei MIE UNIVERSITY,FACULTY OF BIORESOURCES,LECTURER, 生物資源学部, 講師 (90205451)
TAKAMATSU Susumu MIE UNIVERSITY,FACULTY OF BIORESOURCES,ASSISTANT PROFESSOR, 生物資源学部, 助教授 (20260599)
The aim of the research is analysis of the cytoskeletal regulation, which seems to be a molecular basis of plant nonhost resistance, and obtaining basic knowledge for molecular breeding of a plant which is enhanced nonhost resistance. To investigate a change of cytoskeletal organization, barley coleoptile cells which were inoculated with a nonpathogen, Erisiphe pisi, were stained with rhodamine-phalloidin and observed with fluorescent microscope. Actin microfilaments gathered beneath penetration sites of the nonpathogen. When coleoptile cells were treated with actin polymerization inhibitor, cytochalasin, the monpathogen became able to penetnate successfully into nonhost, barley, cells. At the same time, polarization of organelles and defense related responses were suppressed by treatment of the actin inhibitor. The other plants, such as wheat and tobacco, were inculated with nonpathogens, E.pisi and Colletotrichum lagenarium, and reorganization of the actin cytoskeleton and the effects of cytochalasin were investigated. These results showed that the mechanism of nonhost resistance involving the actin cytoskeleton generally exist in many plant species. Because rearrangement of the cytoskeleton is important for the expression of the resistance, we tried to clone actin isoform genes from a barley cDNA libary in order to open a breakthrough of elucidating a regulation of cytoskeletal reorganization. Three major actin isoform genes, Actl, 2 and 3, were cloned and sequenced. When barley coleoptiles were inoculated with E.pisi, the expression level of Act3 was increased specifically. Act3 seems to be involved in making polarization in plant cells, because the gene also strongly expresses in young root tissue, which abundantly contain apical-growing root hairs. Therefore, it is suggested that product of Act3 gene closely related to the expression of nonhost resistance.