Elicitor-induced cytoskeletal rearrangement relates to vacuolar dynamics and execution of cell death: in vivo imaging of hypersensitive cell death in tobacco BY-2 cells.
Disintegration of the vacuolar membrane (VM) has been proposed to be a crucial event in various types of programmed cell death (PCD) in plants. However, its regulatory mechanisms are mostly unknown. To obtain new insights on the regulation of VM disintegration during hypersensitive cell death, we investigated the structural dynamics and permeability of the VM, as well as cytoskeletal reorganization during PCD in tobacco BY-2 cells induced by a proteinaceous elicitor, cryptogein. From sequential observations, we have identified the following remarkable events during PCD. Stage 1: bulb-like VM structures appear within the vacuolar lumen and the cortical microtubules are disrupted, while the cortical actin microfilaments are bundled. Simultaneously, transvacuolar strands including endoplasmic microtubules and actin microfilaments are gradually disrupted and the nucleus moves from the center to the periphery of the cell. Stage 2: cortical actin microfilament bundles and complex bulb-like VM structures disappear. The structure of the large central vacuole becomes simpler, and small spherical vacuoles appear. Stage 3: the VM is disintegrated and a fluorescent dye, BCECF, leaks out of the vacuoles just prior to PCD. Application of an actin polymerization inhibitor facilitates both the disappearance of bulb-like vacuolar membrane structures and induction of cell death. These results suggest that the elicitor-induced reorganization of actin microfilaments is involved in the regulation of hypersensitive cell death via modification of the vacuolar structure to induce VM disintegration.
Higaki
Takumi
T
Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwanoha Kashiwa, Chiba, 277-8562 Japan.
Goh
Tatsuaki
T
Hayashi
Teruyuki
T
Kutsuna
Natsumaro
N
Kadota
Yasuhiro
Y
Hasezawa
Seiichiro
S
Sano
Toshio
T
Kuchitsu
Kazuyuki
K
D000199:Actins / Q000037:antagonists & inhibitors; D020418:Algal Proteins / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D002460:Cell Line; D003599:Cytoskeleton / Q000187:drug effects* / Q000378:metabolism; D005656:Fungal Proteins; D021621:Imaging, Three-Dimensional; D007425:Intracellular Membranes; D010539:Permeability; D013997:Time Factors; D014026:Nicotiana / Q000166:cytology*; D014617:Vacuoles / Q000378:metabolism*
D000199:Actins; D020418:Algal Proteins; D005656:Fungal Proteins; C061032:cryptogein protein, Phytophthora cryptogea