© 2000 Heron Publishing—Victoria, Canada
Characterization of Pin m III cDNA in western white pine
Xueshu Yu (1), Abul K. M. Ekramoddoullah (1, 3) and Santosh Misra (2)
1. Natural Resources Canada, Canadian Forest Service, Pacific Forestry Centre, 506 West Burnside Road, Victoria, BC, V8Z 1M5,
Canada / 2. Department of Biochemistry and Microbiology, University of Victoria, P.O. Box 3055, Victoria, BC, V8W 3P6, Canada / 3. Author to whom correspondence should be addressed (aekramoddoul@pfc.forestry.ca) / Received July 9, 1999
Summary
Maximum accumulation of Pin m III protein in western white pine (Pinus monticola Dougl. ex D. Don) needles occurred during the winter months. To characterize Pin m III, an expression cDNA library from poly(A)+ mRNA
of needles was immunoscreened and the full length cDNA was cloned. An open reading frame of 486 bases encodes a protein of
161 amino acid residues with a molecular mass of 18 kD and a predicted isoelectric point of 5.5. The deduced amino acid sequence
had some similarities (37%) with an intracellular pathogenesis-related (PR) protein from garden asparagus (Asparagus officinalis L.) and the major pollen allergen from white birch (Betula verrucosa J. F. Ehrh.), which are members of the ribonuclease-like PR-10 family. Phylogenetic analysis provided circumstantial evidence
that Pin m III may be grouped with intracellular PRs from asparagus and potato (Solanum tuberosum L.), while the allergens formed another subgroup. Northern analysis showed that the Pin m III gene was preferentially expressed during cold acclimation with the highest expression in the fall and winter months,
preceding the peak of Pin m III protein accumulation. Tissue specificity expression analysis indicated that the gene was strongly
expressed in roots and twigs. Higher amounts of the homologous protein (Pin l I) and its transcript accumulated in sugar pine
(Pinus lambertiana Dougl.) needles infected with blister rust compared with healthy needles.
Keywords:
intracellular PR protein, PR-10 family, seasonal regulation, sugar pine, white pine blister rust.
