title: S-RNase disrupts tip-localized reactive oxygen species and induces nuclear DNA degradation in incompatible pollen tubes of Pyrus pyrifolia.
abstract: Pear (Pyrus pyrifolia L.) has an S-RNase-based gametophytic self-incompatibility (SI) mechanism, and S-RNase has also been implicated in the rejection of self-pollen and genetically identical pollen. However, RNA degradation might be only the beginning of the SI response, not the end. Recent in vitro studies suggest that S-RNase triggers mitochondrial alteration and DNA degradation in the incompatible pollen tube of Pyrus pyrifolia, and it seems that a relationship exists between self S-RNase, actin depolymerization and DNA degradation. To further uncover the SI response in pear, the relationship between self S-RNase and tip-localized reactive oxygen species (ROS) was evaluated. Our results show that S-RNase specifically disrupted tip-localized ROS of incompatible pollen tubes via arrest of ROS formation in mitochondria and cell walls. The mitochondrial ROS disruption was related to mitochondrial alteration, whereas cell wall ROS disruption was related to a decrease in NADPH. Tip-localized ROS disruption not only decreased the Ca(2+) current and depolymerized the actin cytoskeleton, but it also induced nuclear DNA degradation. These results indicate that tip-localized ROS disruption occurs in Pyrus pyrifolia SI. Importantly, we demonstrated nuclear DNA degradation in the incompatible pollen tube after pollination in vivo. This result validates our in vitro system in vivo.
authors.affiliation: College of Horticulture, State Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, Nanjing 210095, China.
authors.forename: Chun-Lei
authors.initials: CL
authors.lastname: Wang
authors.forename: Jun
authors.initials: J
authors.lastname: Wu
authors.forename: Guo-Hua
authors.initials: GH
authors.lastname: Xu
authors.forename: Yong-Bin
authors.initials: YB
authors.lastname: Gao
authors.forename: Gong
authors.initials: G
authors.lastname: Chen
authors.forename: Ju-You
authors.initials: JY
authors.lastname: Wu
authors.forename: Hua-Qing
authors.initials: HQ
authors.lastname: Wu
authors.forename: Shao-Ling
authors.initials: SL
authors.lastname: Zhang
mesh_terms: D020013:Calcium Signaling; D002467:Cell Nucleus / Q000378:metabolism*; D003599:Cytoskeleton / Q000378:metabolism; D053938:DNA Fragmentation; D005453:Fluorescence; D006861:Hydrogen Peroxide / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D053205:Pollen Tube / Q000166:cytology / Q000201:enzymology* / Q000648:ultrastructure; D054817:Pollination / Q000502:physiology; D058105:Polymerization; D031989:Pyrus / Q000166:cytology* / Q000201:enzymology* / Q000648:ultrastructure; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012260:Ribonucleases / Q000378:metabolism*; D013104:Spheroplasts / Q000166:cytology / Q000378:metabolism
chemical_list: D017382:Reactive Oxygen Species; D009249:NADP; D006861:Hydrogen Peroxide; D012260:Ribonucleases; C022542:ribonuclease S