Conifer forests worldwide are becoming increasingly vulnerable to the effects of climate
change. Although the production of phenolic compounds (PCs) has been shown to
be modulated by biotic and abiotic stresses, the genetic basis underlying the variation
in their constitutive production level remains poorly documented in conifers. We used
QTL mapping and RNA-Seq to explore the complex polygenic network underlying the
constitutive production of PCs in a white spruce (Picea glauca) full-sib family for 2 years.
QTL detection was performed for nine PCs and differentially expressed genes (DEGs)
were identified between individuals with high and low PC contents for five PCs exhibiting
stable QTLs across time. A total of 17 QTLs were detected for eightmetabolites, including
one major QTL explaining up to 91.3% of the neolignan-2 variance. The RNA-Seq
analysis highlighted 50 DEGs associated with phenylpropanoid biosynthesis, several key
transcription factors, and a subset of 137 genes showing opposite expression patterns
in individuals with high levels of the flavonoids gallocatechin and taxifolin glucoside. A
total of 19 DEGs co-localized with QTLs. Our findings represent a significant step toward
resolving the genomic architecture of PC production in spruce and facilitate the functional
characterization of genes and transcriptional networks responsible for differences in
constitutive production of PCs in conifers.National Sciences and Engineering Research Council of Canada, the Spruce-Up LSARP project with funding from Genome Canada and Genome Quebec and Genomics Research and Development Initiative of Canada.http://www.frontiersin.org/Plant_Scienceam2022Forestry and Agricultural Biotechnology Institute (FABI)Zoology and Entomolog
