Characterization of the western white pine TIR-NBS-LRR (PmTNL2) gene by transcript profiling and promoter analysis

Proteins with nucleotide-binding site (NBS) and leucine-rich repeats (LRRs) have been reported to play important roles in plant disease resistance, growth, and development. However, no comprehensive analysis of this protein family has been performed in conifers. Here we report that the Pinus monticola PmTNL2 gene is a member of the NBS-LRR superfamily. Quantitative reverse transcription-PCR (qRT-PCR) analysis revealed that the PmTNL2 transcript was expressed in a tissue-specific pattern with extensive regulation by various environmental stimuli in western white pine seedlings, suggesting its wide involvement in stress defense and diverse developmental processes. In silico analysis of the PmTNL2 promoter region revealed multiple cis-regulatory elements characterized with potential functions for development-, light-, and stress-regulated transcript expression. Expression patterns were largely confirmed by PmTNL2 promoter-directed reporter gene expression using stable transgenic Arabidopsis plants. Notably, the PmTNL2 promoter activity was highly expressed in shoot apical and floral meristems and was induced strongly with vascular specificity by pathogen infection. Our data has provided a fundamental insight into both expression regulation and putative functions of the PmTNL2 gene in the context of plant growth and development, as well as in responses to environmental stressors. Promoter application as a potential tool for tree improvement was further discussed.