© 2007 Heron Publishing—Victoria, Canada
Identification of two thaumatin-like proteins (TLPs) in the pollination drop of hybrid yew that may play a role in pathogen
defence during pollen collection
Stephen J. B. O'Leary (1, 2, 3), Brett A. D. Poulis (1) and Patrick von Aderkas (1)
1. Graduate Centre for Forest Biology, Department of Biology, University of Victoria, Victoria, BC V8W 3N5, Canada / 2. Present address: National Research Council, Institute for Marine Biosciences, 1411 Oxford St., Halifax, NS B3H 3Z1, Canada / 3. Corresponding author (stephen.oleary@nrc-cnrc.gc.ca) / Received December 29, 2006; accepted March 10, 2007; published online September 4, 2007
Summary
We describe the proteomic identification of two pathogenesis-related group 5 (PR-5) proteins, an acidic thaumatin-like protein
(TLP) and a basic TLP isolated from the pollination drop of hybrid yew (Taxus × media Rehder). The basic TLP (TxmTLPb) was the most abundant protein in the yew pollination drop based on protein spot size after
two-dimensional electrophoresis. The acidic TLP (TxmTLPa) is also a major protein component of the yew ovular secretion and
appears to be encoded by a number of mRNAs transcribed from a TLP gene family that has undergone limited sequence divergence.
We have sequenced five acidic TLP-encoding cDNAs (TxmTLPa-1,2,3,4 and 5) isolated from the yew ovule that vary from each other by no more than five out of 233 amino acid residues in their predicted
protein sequences. All of the cDNA variants encode TLPs possessing the 16 conserved cysteine residues and five charged amino
acid side chains associated with antifungal activity. Amplification of genomic DNA with TxmTLPa primers indicated that at least 11 acidic TLPs with highly similar amino acid sequences may be expressed in yew tissues.
Antibodies against TLPs confirmed the identity of TxmTLPa and TxmTLPb in the yew pollination drop and detected TLPs in the
ovular secretions of four other species from three other conifer families. Our results suggest that TLPs are a conserved component
of conifer ovular secretions and are involved in broad spectrum pathogen defence of ovules.
Keywords:
antifungal, conifer reproduction, gene family, ovular secretion, PR-5 protein, proteomics.
