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UBC Theses and Dissertations

Phylogenomic analysis of the transcriptome of spruce (genus Picea) Albouyeh, Rokneddin M.


Trees are sessile and exposed to a plethora of pests throughout their life-span and natural history. Diversification of the specialized (secondary) metabolism is known as a key factor in the co-evolution of trees with pests. This work focuses on tissue-related gene expression, and the expression of specialized pathways of phenolics and terpenoids in relation to the evolution of biochemical defenses in the coniferous species of spruce (genus Picea). Gene expression resources were assessed for the superimposition of tissue-related expression and cross-species expression profiling. Five species of spruce, P. abies, P. glauca, P. jezoensis, P. omorika, and P. mariana, were used to infer the evolution of gene expression among representative spruce species. As gene expression also depends upon tissue, I examined three sources of tissue: needles, outer stem (bark and the attached phloem) and xylem. The overall expression of phenolics was significantly diverged in the outer stem. At the gene family level, expression was predominantly stabile among species. Significant among-species divergence of gene expression, indicative of diversifying selection, was found for eight gene families. These families were: cinnamate 4- hydroxylases (C4H), dirigent-like proteins (DIR), glycosyl transferases (GLYTR), laccases (LAC), O-methyl transferases (OMT), phenylalanine ammonia lyases (PAL), putative caffeoyl CoA O-methyl transferases (pCCoAOMT) and putative phenylcoumaran benzylic ether reductases (pPCBER). Analysis of the expression of the terpenoid pathways in the outer stem revealed that for terpene synthase gene family (TPS), expression is significantly diverged among species. In a novel approach, heritability of gene expression using parent-offspring regression was inferred for Interior spruce (P. glauca x engelmannii), and average expression for TPS genes showed substantial heritability.

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