Cloning and characterization of NtTMK1 gene encoding a TMK1-homologous receptor-like kinase in tobacco

A cDNA encoding a receptor-like kinase, designated NtTMK1, was isolated from Nicotiana tabacum. The kinase domain of NtTMK1 contained all of 12 subdomains and invariant amino acid residues found in eukaryotic protein kinases. The extracellular domain contained 11 leucine-rich repeats which have been implicated in protein-protein interactions. The amino acid sequence of NtTMK1 exhibited high homology with those of TMK1 of Arabidopsis and TMK of rice in both kinase and extracellular domains, suggesting that NtTMK1 is a TMK homologue of tobacco. The NtTMK1 transcripts were present in all major plant organs, but its level varied in different developmental stages in anthers and floral organs. NtTMK1 mRNA accumulation in leaves was stimulated by CaCl₂, methyl jasmonate, wounding, fungal elicitors, chitins, and chitosan. The NtTMK1 mRNA level also increased upon infection with tobacco mosaic virus.