Supporting Data for: Differential gene expression associated with a floral scent polymorphism in the evening primrose Oenothera harringtonii (Onagraceae)

Background: Plant volatiles play an important role in both
plant-pollinator and plant-herbivore interactions. Intraspecific
polymorphisms in volatile production are ubiquitous, but studies that
explore underlying differential gene expression are rare. Oenothera
harringtonii populations are polymorphic in floral emission of the
monoterpene (R)-(-)-linalool; some plants emit (R)-(-)-linalool (linalool+
plants) while others do not (linalool- plants). However, the genes
associated with differential production of this floral volatile in
Oenothera are unknown. We used RNA-Seq to broadly characterize
differential gene expression involved in (R)-(-)-linalool biosynthesis. To
identify genes that may be associated with the polymorphism for this
trait, we used RNA-Seq to compare gene expression in six different
Oenothera harringtonii tissues from each of three linalool+ and linalool-
plants. Results: Three clusters of differentially expressed genes were
enriched for terpene synthase activity: two were characterized by
tissue-specific upregulation and one by upregulation only in plants with
flowers that produce (R)-(-)-linalool. A molecular phylogeny of all
terpene synthases identified two putative (R)-(-)-linalool synthase
transcripts in Oenothera harringtonii, a single allele of which is found
exclusively in linalool+ plants. Conclusions: By using a naturally
occurring polymorphism and comparing different tissues, we were able to
identify genes putatively involved in the biosynthesis of
(R)-(-)-linalool. Expression of these genes in linalool- plants suggests a
regulatory polymorphism, rather than a population-specific
loss-of-function allele. Additional terpene biosynthesis-related genes
that are up-regulated in plants that emit (R)-(-)-linalool may be
associated with herbivore defense, suggesting a potential economy of scale
between plant reproduction and defense.