Targeted proteomics using selected reaction monitoring
reveals the induction of specific terpene synthases in a
multi-level study of methyl jasmonate-treated Norway
spruce (Picea abies)Induction of terpene synthase (TPS) gene expression and enzyme activity is known to occur in response to
various chemical and biological stimuli in several species of spruce (genus Picea). However, high sequence
identity between TPS family members has made it difficult to determine the induction patterns of individual
TPS at the protein and transcript levels and whether specific TPS enzymes respond differentially to treatment.
In the present study we used a multi-level approach to measure the induction and activity of TPS enzymes in
protein extracts of Norway spruce (Picea abies) bark tissue following treatment with methyl jasmonate
(MeJA). Measurements were made on the transcript, protein, enzyme activity and metabolite levels. Using a
relatively new proteomics application, selective reaction monitoring (SRM), it was possible to differentiate
and quantitatively measure the abundance of several known TPS proteins and three 1-deoxy-D-xylulose
5-phosphate synthase (DXS) isoforms inNorwayspruce. Protein levels of individualTPSandDXSenzymes were
differentially induced upon MeJA treatment and good correlation was generally observed between induction
of transcripts, proteins, and enzyme activities. Most of the mono- and diterpenoid metabolites accumulated
with similar temporal patterns of induction as part of the coordinated multi-compound chemical defense
response. Protein and enzyme activity levels of the monoTPS (+)-3-carene synthase and the corresponding
accumulation of (+)-3-carene was induced to a higher fold change than any other TPS or metabolite measured,
indicating an important role in the induced terpenoid defense response in Norway spruce.
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