title: ROS-induced oxidative stress and apoptosis-like event directly affect the cell viability of cryopreserved embryogenic callus in Agapanthus praecox.
abstract: Oxidative stress and apoptosis-like programmed cell death, induced in part by H 2 O 2 , are two key factors that damage cells during plant cryopreservation. Their inhibition can improve cell viability. We hypothesized that oxidative stress and apoptosis-like event induced by ROS seriously impact plant cell viability during cryopreservation. This study documented changes in cell morphology and ultrastructure, and detected dynamic changes in ROS components (O 2 (·-) , H2O2 and OH·), antioxidant systems, and programmed cell death (PCD) events during embryonic callus cryopreservation of Agapanthus praecox. Plasmolysis, organelle ultrastructure changes, and increases in malondialdehyde (a membrane lipid peroxidation product) suggested that oxidative damage and PCD events occurred at several early cryopreservation steps. PCD events including autophagy, apoptosis-like, and necrosis also occurred at later stages of cryopreservation, and most were apoptosis. H2O2 is the most important ROS molecule mediating oxidative damage and affecting cell viability, and catalase and AsA-GSH cycle are involved in scavenging the intracellular H2O2 and protecting the cells against stress damage in the whole process. Gene expression studies verified changes of antioxidant system and PCD-related genes at the main steps of the cryopreservation process that correlated with improved cell viability. Reducing oxidative stress or inhibition of apoptosis-like event by deactivating proteases improved cryopreserved cell viability from 49.14 to 86.85 % and 89.91 %, respectively. These results verify our model of ROS-induced oxidative stress and apoptosis-like event in plant cryopreservation. This study provided a novel insight into cell stress response mechanisms in cryopreservation.
authors.affiliation: Key Laboratory of Urban Agriculture (South) Ministry of Agriculture, School of Agriculture and Biology, Shanghai Jiao Tong University, No. 800, Rd. Dong Chuan, Shanghai, People's Republic of China.
authors.forename: Di
authors.initials: D
authors.lastname: Zhang
authors.forename: Li
authors.initials: L
authors.lastname: Ren
authors.forename: Guan-Qun
authors.initials: GQ
authors.lastname: Chen
authors.forename: Jie
authors.initials: J
authors.lastname: Zhang
authors.forename: Barbara M
authors.initials: BM
authors.lastname: Reed
authors.forename: Xiao-Hui
authors.initials: XH
authors.lastname: Shen
mesh_terms: D000975:Antioxidants / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects*; D001343:Autophagy / Q000187:drug effects; D048430:Cell Shape / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D015925:Cryopreservation; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D020287:In Situ Nick-End Labeling; D019668:Liliaceae / Q000166:cytology* / Q000196:embryology* / Q000235:genetics / Q000648:ultrastructure; D015227:Lipid Peroxidation / Q000187:drug effects; D008315:Malondialdehyde / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects*; D017382:Reactive Oxygen Species / Q000633:toxicity*; D060888:Real-Time Polymerase Chain Reaction; D012639:Seeds / Q000166:cytology* / Q000187:drug effects / Q000648:ultrastructure
chemical_list: D000975:Antioxidants; D017382:Reactive Oxygen Species; D008315:Malondialdehyde