Actin-related defense mechanism to reject penetration attempt by a non-pathogen is maintained in tobacco BY-2 cells.
The actin cytoskeleton is a key player in defense responses during early stages of infection by fungal pathogens. To investigate molecular mechanisms of actin-related defense responses, a cultured tobacco ( Nicotiana tabacum L.) BY-2 cell system was devised. When conidia were directly deposited on BY-2 cells, neither a pathogen, Erysiphe cichoracearum, nor a non-pathogen, Erysiphe pisi, was able to form appressoria or haustoria on BY-2 cells. On the other hand, conidia of the powdery mildews formed appressoria on BY-2 cells if they were covered with a thin hydrophobic membrane of Formvar. Percentages of appressoria formation of the powdery mildews on the Formvar-covered BY-2 cells were mostly the same as those on leaf epidermal cells. The pathogen successfully penetrated through the membrane into BY-2 cells and formed haustoria, whereas penetration attempts of the non-pathogen were completely rejected by the BY-2 cells similar to attempts on leaf epidermal cells. On the other hand, when BY-2 cells were treated with actin cytoskeleton-depolymerizing agents, cytochalasins, the non-pathogen became able to penetrate and form haustoria in BY-2 cells. Simultaneously, cytochalasin inhibited callose deposition at penetration sites of the non-pathogen. These results demonstrated that the actin cytoskeleton plays an important role in defense mechanisms against fungal penetration, even in the dedifferentiated cultured cells. The newly devised Formvar-covered cultured cell system will be a useful tool for molecular dissection of signal perception and defense mechanisms of plant cells during the early stage of fungal attack.
Laboratory of Plant Infection, Faculty of Bioresources, Mie University, 514-8507, Tsu, Japan. issei@bio.mie-u.ac.jp
Issei
I
Kobayashi
Humiaki
H
Hakuno
D000199:Actins / Q000378:metabolism*; D003599:Cytoskeleton / Q000378:metabolism; D005658:Fungi / Q000472:pathogenicity / Q000502:physiology*; D007113:Immunity, Innate; D010935:Plant Diseases / Q000382:microbiology; D011145:Polyvinyls / Q000494:pharmacology; D013045:Species Specificity; D014026:Nicotiana / Q000166:cytology / Q000187:drug effects / Q000382:microbiology* / Q000502:physiology*
D000199:Actins; D011145:Polyvinyls; C013215:polyvinyl acetate