Phosphorylation of Coat Protein by Protein Kinase CK2 Regulates Cell-to-Cell Movement of Bamboo mosaic virus Through Modulating RNA Binding

• Published in: Molecular plant-microbe interactions Vol. 27; no. 11; pp. 1211 - 1225
• Main Authors: Hung, Chien-Jen, Huang, Ying-Wen, Liou, Ming-Ru, Lee, Ya-Chien, Lin, Na-Sheng, Meng, Menghsiao, Tsai, Ching-Hsiu, Hu, Chung-Chi, Hsu, Yau-Heiu
• Format: Journal Article
• Language: English
• Published: United States The American Phytopathological Society 01.11.2014
• Subjects: alanine; Amino Acid Sequence; Bamboo mosaic virus; binding capacity; Capsid Proteins - genetics; Capsid Proteins - metabolism; Casein Kinase II - genetics; Casein Kinase II - metabolism; coat proteins; Genes, Reporter; Models, Biological; Molecular Sequence Data; Mutation; Nicotiana - cytology; Nicotiana - enzymology; Nicotiana - genetics; Nicotiana - virology; Nicotiana benthamiana; non-specific serine/threonine protein kinase; Phosphorylation; Plant Diseases - virology; Plant Leaves - cytology; Plant Leaves - enzymology; Plant Leaves - genetics; Plant Leaves - virology; Plant Proteins - genetics; Plant Proteins - metabolism; plasmodesmata; Plasmodesmata - virology; Potexvirus - genetics; Potexvirus - physiology; Potexvirus - ultrastructure; Protein Binding; Recombinant Fusion Proteins; RNA; RNA, Viral - genetics; serine; threonine
• ISSN: 0894-0282; 1943-7706
• DOI: 10.1094/MPMI-04-14-0112-R

In this study, we investigated the fine regulation of cell-to-cell movement of Bamboo mosaic virus (BaMV). We report that the coat protein (CP) of BaMV is phosphorylated in planta at position serine 241 (S241), in a process involving Nicotiana benthamiana casein kinase 2α (NbCK2α). BaMV CP and NbCK2α colocalize at the plasmodesmata, suggesting that phosphorylation of BaMV may be involved in its movement. S241 was mutated to examine the effects of temporal and spatial dysregulation of phosphorylation on i) the interactions between CP and viral RNA and ii) the regulation of cell-to-cell movement. Replacement of S241 with alanine did not affect RNA binding affinity but moderately impaired cell-to-cell movement. A negative charge at position 241 reduced the ability of CP to bind RNA and severely interfered with cell-to-cell movement. Deletion of residues 240 to 242 increased the affinity of CP to viral RNA and dramatically impaired cell-to-cell movement. A threonine at position 241 changed the binding preference of CP toward genomic RNA and inhibited cell-to-cell movement. Together, these results reveal a fine regulatory mechanism for the cell-to-cell movement of BaMV, which involves the modulation of RNA binding affinity through appropriate phosphorylation of CP by NbCK2α.