Bax-induced cell death of Arabidopsis is meditated through reactive oxygen-dependent and -independent processes.
An Arabidopsis protoplast system was developed for dissecting plant cell death in individual cells. Bax, a mammalian pro-apoptotic member of the Bcl-2 family, induces apoptotic-like cell death in Arabidopsis. Bax accumulation in Arabidopsis mesophyll protoplasts expressing murine Bax cDNA from a glucocorticoid-inducible promoter results in cytological characteristics of apoptosis, namely DNA fragmentation, increased vacuolation, and loss of plasma membrane integrity. In vivo targeting analysis monitored using jellyfish green fluorescent protein (GFP) reporter indicated full-length Bax was localized to the mitochondria, as it does in animal cells. Deletion of the carboxyl-terminal transmembrane domain of Bax completely abolished targeting to mitochondria. Bax expression was followed by reactive oxygen species (ROS) accumulation. Treatment of protoplasts with the antioxidant N -acetyl- -cysteine (NAC) during induction of Bax expression strongly suppressed Bax-mediated ROS production and the cell death phenotype. However, some population of the ROS depleted cells still induced cell death, indicating that there is a process that Bax-mediated plant cell death is independent of ROS accumulation. Accordingly, suppression of Bax-mediated plant cell death also takes place in two different processes. Over-expression of a key redox-regulator, Arabidopsis nucleoside diphosphate kinase 2 (AtNDPK2) down-regulated ROS accumulation and suppressed Bax-mediated cell death and transient expression of Arabidopsis Bax inhibitor-1 (AtBI-1) substantially suppressed Bax-induced cell death without altering cellular ROS level. Taken together, our results collectively suggest that the Bax-mediated cell death and its suppression in plants is mediated by ROS-dependent and -independent processes.
Baek
Dongwon
D
Environmental Biotechnology National Core Research Center, and Division of Applied Life Science (BK21 program), Graduate School of Gyeongsang National University, Jinju, 660-701, Korea.
Nam
Jaesung
J
Koo
Yoon Duck
YD
Kim
Doh Hoon
DH
Lee
Jiyoung
J
Jeong
Jae Cheol
JC
Kwak
Sang-Soo
SS
Chung
Woo Sik
WS
Lim
Chae Oh
CO
Bahk
Jeong Dong
JD
Hong
Jong Chan
JC
Lee
Sang Yeol
SY
Kawai-Yamada
Maki
M
Uchimiya
Hirofumi
H
Yun
Dae-Jin
DJ
D000818:Animals; D017209:Apoptosis; D017360:Arabidopsis / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000502:physiology; D048429:Cell Size; D053938:DNA Fragmentation; D003907:Dexamethasone / Q000494:pharmacology; D015870:Gene Expression; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology; D051379:Mice; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000378:metabolism; D008954:Models, Biological; D030821:Plants, Genetically Modified; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000502:physiology*; D011523:Protoplasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D013997:Time Factors; D014170:Transformation, Genetic; D014617:Vacuoles / Q000378:metabolism; D051028:bcl-2-Associated X Protein; D000097573:Red Fluorescent Protein
D029681:Arabidopsis Proteins; D003907:Dexamethasone; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins; D008565:Membrane Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D011993:Recombinant Fusion Proteins; D051028:bcl-2-Associated X Protein; D000097573:Red Fluorescent Protein; C491862:ATBI-1 protein, Arabidopsis; C494827:Bax protein, mouse