Abstract
Cell wall-associated kinases (WAKs) are a class of receptor-like protein kinases with a cytoplasmic serine/threonine kinase and a pectin-binding extracellular domain. Although the structure suggests that WAKs are involved in signaling between cell walls and cytoplasm, their function is largely unknown. Here we present a cloning and characterization of a WAK-like protein of suspension-cultured tobacco BY-2 cells.
We searched nicotiana EST database and identified NtWAKL1 (Nicotiana tabacum WAK-like protein 1) with an extracellular epidermal growth factor-like sequence and a cytoplasmic kinase. NtWAKL1 is most similar to Arabidopsis WAKL20. Immunoblot analysis detected bands with a mobility that corresponded to >250 kD, which disappeared upon pectinase treatment of the cell. Confocal microscopic analysis localized NtWAKL1-GFP fusion protein at cell surface, but the fluorescence moved away from the cell wall upon plasmolysis. These results suggest that although NtWAKL1 somehow interacts with pectin, the extracellular domain is not immobilized within the cell wall.
