Canadian Forest Service Publications

Characterization of the western white pine TIR-NBS-LRR (PmTNL2) gene by transcript profiling and promoter analyses. 2019. Liu, J.-J., Xiang, Y. Genome, 62(7): 477-488.

Year: 2019

Issued by: Pacific Forestry Centre

Catalog ID: 40022

Language: English

Availability: PDF (request by e-mail)

Available from the Journal's Web site.
DOI: 10.1139/gen-2019-0035

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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.

Plain Language Summary

Characterization of host resistance (R) genes provides essential knowledge and tools for breeding improvement of forest resistance to pests and pathogens. Most plant R proteins are members of a superfamily that share domains of the nucleotide-binding site (NBS) and leucine-rich repeats (LRRs). We identified a western white pine gene (PmTNL2) encoding an NBS-LRR protein with a toll/interleukin 1 receptor (TIR) domain at the C-terminus. We revealed its putative protein structure, expression profiles, and its promoter activities to understand the transcription regulation of this gene and understand its implication to biological processes. Both environmental stimuli (including rust infection, cold-hardiness, and wounding) and developmental stages significantly regulated PmTNL2 expression in white pine seedlings. We further confirmed PmTNL2 expression profiles by identification of cis-elements in the PmTNL2 promoter region and stable expression of promoter:: Gus fusion gene in Arabidopsis plants. Notably, we found strong promoter activity in stem and floral meristems with high inducibility with vascular specificity by pathogen infection. Our results imply that PmTNL2 plays functional roles in both plant development and defense responses in western white pine. The disease-inducible and tissue-specific promoter we identified here would be useful for biotechnological improvement of trees with better fitness to changing climates.