Heterotrimeric G-protein is involved in phytochrome A-mediated cell death of Arabidopsis hypocotyls

• Published in: Cell research Vol. 18; no. 9; pp. 949 - 960
• Main Authors: Wei, Qing, Zhou, Wenbin, Hu, Guangzhen, Wei, Jiamian, Yang, Hongquan, Huang, Jirong
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.09.2008; Nature Publishing Group
• Subjects: Arabidopsis; Arabidopsis - cytology; Arabidopsis - drug effects; Arabidopsis - enzymology; Arabidopsis Proteins - metabolism; Biomedical and Life Sciences; Cell Biology; Cell death; Cell Death - drug effects; Chloroplasts - drug effects; Chloroplasts - metabolism; Gene Expression Regulation, Plant - drug effects; Heterotrimeric GTP-Binding Proteins - metabolism; Hydrogen peroxide; Hydrogen Peroxide - pharmacology; Hypocotyl - cytology; Hypocotyl - drug effects; Hypocotyl - enzymology; Irradiation; Life Sciences; Membrane Proteins - metabolism; Microscopy, Fluorescence; Molecular Mimicry - drug effects; Mortality; Mutants; Mutation - genetics; original-article; Oxidoreductases Acting on CH-CH Group Donors - genetics; Oxidoreductases Acting on CH-CH Group Donors - metabolism; Phytochrome A - metabolism; Protochlorophyllide - metabolism; Seedlings; 植物色素A; 细胞死亡; 鸟嘌呤; phytochrome A; cell death; Pchlide; ROS; heterotrimeric G protein
• ISSN: 1001-0602; 1748-7838
• DOI: 10.1038/cr.2008.271

The heterotrimeric guanine nucleotide-binding protein （G-protein） has been demonstrated to mediate various signaling pathways in plants. However, its role in phytochrome A （phyA） signaling remains elusive. In this study, we discover a new phyA-mediated phenotype designated far-red irradiation （FR） preconditioned cell death, which occurs only in the hypocotyls of FR-grown seedlings following exposure to white light （WL）. The cell death is mitigated in the Gα mutant gpal but aggravated in the Gβ mutant agbl in comparison with the wild type （WT）, indicative of antagonistic roles of GPA1 and AGBI in the phyA-mediated cell-death pathway. Further investigation indicates that FR-induced accumulation of nonphotoconvertible protochlorophyllide （Pchlide^633）, which generates reactive oxygen species （ROS） on exposure to WL, is required for FR-preconditioned cell death. Moreover, ROS is mainly detected in chloroplasts using the fluorescent probe. Interestingly, the application of H2O2 to dark-grown seedlings results in a phenotype similar to FR-preconditioned cell death. This reveals that ROS is a critical mediator for the ceil death. In addition, we observe that agb1 is more sensitive to H2O2 than WT seedlings, indicating that the G-protein may also modify the sensitivity of the seedlings to ROS stress. Taking these results together, we infer that the G-protein may be involved in the phyA signaling pathway to regulate FR-preconditioned cell death ofArabidopsis hypocotyls. A possible mechanism underlying the involvement of the G-protein in phyA signaling is discussed in this study.