An apple CIPK protein kinase targets a novel residue of AREB transcription factor for ABA‐dependent phosphorylation

• Published in: Plant, cell and environment cell and environment, 2017-10, Vol.40 (10), p.2207-2219
• Main Authors: Ma, Qi‐Jun, Sun, Mei‐Hong, Lu, Jing, Liu, Ya‐Jing, You, Chun‐Xiang, Hao, Yu‐Jin
• Format: Article
• Language: English
• Subjects: ABA; abiotic stress; Abscisic acid; Abscisic Acid - metabolism; apple; Apples; callus; cDNA libraries; complementary DNA; Fruits; Gene Expression Regulation, Plant; gene overexpression; genes; Genes, Plant; Homology; Hybridization; Kinases; Malus - enzymology; Malus - genetics; MdAREB2; MdCIPK22; Phosphorylation; Plant hormones; Plant Proteins - metabolism; Plantlets; Plants, Genetically Modified; Protein Binding; Protein kinase; protein kinases; Protein Kinases - metabolism; Proteins; Researchers; Sensitivity analysis; Signal processing; Signal transduction; Signaling; Stability; stress response; Threonine - metabolism; transcription (genetics); Transcription factors; Transcription Factors - metabolism; Transcription, Genetic; Transgenic plants; Yeast; Yeasts
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/pce.13013

Phytohormone abscisic acid (ABA) regulates many important processes in plants. It is a major molecule facilitating signal transduction during the abiotic stress response. In this study, an ABA‐inducible transcription factor gene, MdAREB2, was identified in apple. Transgenic analysis was performed to characterize its function in ABA sensitivity. Overexpression of the MdAREB2 gene increased ABA sensitivity in the transgenic apple compared with the wild‐type (WT) control. In addition, it was found that the protein MdAREB2 was phosphorylated at a novel site Thr411 in response to ABA. A yeast two‐hybridization screen of an apple cDNA library demonstrated that a protein kinase, MdCIPK22, interacted with MdAREB2. Their interaction was further verified with Pull Down and Co‐IP assays. A series of transgenic analyses in apple calli and plantlets showed that MdCIPK22 was required for ABA‐induced phosphorylation at Thr411 of the MdAREB2 protein and enhanced its stability and transcriptional activity. Finally, it was found that MdCIPK22 increased ABA sensitivity in an MdAREB2‐dependent manner. Our findings indicate a novel phosphorylation site in CIPK‐AREB regulatory module for the ABA signalling pathway, which would be helpful for researchers to identify the functions of uncharacterized homologs in the future. An abscisic acid (ABA)‐inducible transcription factor gene MdAREB2 was involved in ABA sensitivity and phosphorylated at a novel site Thr411 in response to ABA. MdCIPK22 was required for ABA‐induced phosphorylation at Thr411 of the MdAREB2 protein and enhanced its stability and transcriptional activity. A novel phosphorylation site in CIPK‐AREB regulatory module for the ABA signalling pathway, which would be helpful for researchers to identify the functions of uncharacterized homologs in the future.