Two Rice Authentic Histidine Phosphotransfer Proteins, OsAHP1 and OsAHP2, Mediate Cytokinin Signaling and Stress Responses in Rice

• Published in: Plant physiology (Bethesda) 2014-05, Vol.165 (1), p.335-345
• Main Authors: Sun, Lijing, Zhang, Qian, Wu, Jinxia, Zhang, Liqing, Jiao, Xuewen, Zhang, Shengwei, Zhang, Zhiguo, Sun, Daye, Lu, Tiegang, Sun, Ying
• Format: Article
• Language: English
• Subjects: Cell Nucleus - drug effects; Cell Nucleus - metabolism; Cytokinins; Cytokinins - metabolism; Cytokinins - pharmacology; Cytosol - drug effects; Cytosol - metabolism; Drought; drought tolerance; Gene expression regulation; Histidine; Oryza - genetics; Oryza - growth & development; Oryza - metabolism; Oryza - physiology; Osmotic Pressure - drug effects; Phenotype; Phosphorylation - drug effects; Plant Development - drug effects; Plant Proteins; Plant roots; Plant Roots - anatomy & histology; Plant Roots - drug effects; Plants; Plants, Genetically Modified; proteins; Regulator genes; Rice; RNA Interference - drug effects; Seedlings; Seedlings - drug effects; Seedlings - physiology; Seminal roots; signal transduction; Signal Transduction - drug effects; SIGNALING AND RESPONSE; Sodium Chloride - pharmacology; stress response; Stress, Physiological - drug effects; Transgenic plants
• ISSN: 0032-0889; 1532-2548; 1532-2548
• DOI: 10.1104/pp.113.232629

Cytokinin plays an important role in plant development and stress tolerance. Studies of Arabidopsis (Arabidopsis thaliana) have demonstrated that cytokinin acts through a two-component system that includes a histidine (His) kinase, a His phosphotransfer protein (HP), and a response regulator. Phylogenetic analyses have revealed the conservation of His kinases but lineage-specific expansion of HPs and response regulators in rice (Oryza sativa). However, whether the functions of rice HPs have diverged remains unknown. In this study, two rice authentic HPs (OsAHP1 and OsAHP2) were knocked down simultaneously via RNA interference (RNAi), and the transgenic OsAHP-RNAi plants exhibited phenotypes expected for a deficiency in cytokinin signaling, including dwarfism with reduced internode lengths, enhanced lateral root growth, early leaf senescence, and reduced tiller numbers and fertility under natural conditions. The OsAHP-RNAi seedlings were also hyposensitive to exogenous cytokinin. Furthermore, OsAHP-RNAi seedlings were hypersensitive to salt treatment but resistant to osmotic stress relative to wild-type plants. These results indicate that OsAHPs function as positive regulators of the cytokinin signaling pathway and play different roles in salt and drought tolerance in rice.