Abstract
Incidence of natural light stress renders it important to enhance our understanding of the mechanisms by which plants protect themselves from harmful effects of UV-B irradiation, as this is critical for fitness of land plant species. Here we describe natural variation of a class of phenylacylated-flavonols (saiginols), which accumulate to high levels in floral tissues of Arabidopsis. They were identified in a subset of accessions, especially those deriving from latitudes between 16° and 43° North. Investigation of introgression line populations using metabolic and transcript profiling, combined with genomic sequence analysis, allowed the identification of flavonol-phenylacyltransferase 2 (FPT2) that is responsible for the production of saiginols and conferring greater UV light tolerance in planta. Furthermore, analysis of polymorphism within the FPT duplicated region provides an evolutionary framework of the natural history of this locus in the Brassicaceae.
Highlights
Incidence of natural light stress renders it important to enhance our understanding of the mechanisms by which plants protect themselves from harmful effects of UV-B irradiation, as this is critical for fitness of land plant species
We studied the natural variation of floral secondary metabolites among Arabidopsis accessions, characterizing a novel class of phenylacylated-flavonols and a flavonol-phenylacyltransferase 2 (FPT2) gene corresponding to altered in planta UV-B light tolerance
Our hypothesized evolutionary framework for genes in this gene cluster is summarized in Fig. 5e with speciation tree based on NCBI taxonomic analysis
Summary
On the basis of the core chemical structure and decoration pattern of saiginol A, their retention times and the MS/MS experiments described above we were able to impute the chemical structure (Supplementary Fig. 3) and putative biosynthetic paths for the other unknown peaks, which we subsequently collectively refer to as saiginols (Fig. 1c) These peaks, we named as saiginols B-R, are putatively characterized by the presence or absence of three possible aglycones (kaempferol, quercetin and isorhamnetin) and by having one of three types of phenylacylation (sinapoyl, caffeoyl and p-coumaroyl moieties) based on annotation by fragmentation of MS/MS and elution time profile (Supplementary Data 1). Que-3G6′′Sin-7R (J) Que-3G6′′Caf-7R (K) Que-3G6′′pCou-7R (L) Que-3G2′′R6′′Sin-7R (G) Que-3G2′′R6′′Caf-7R (H) Que-3G2′′R6′′pCou-7R (I) Iso-3G6′′Sin-7R (P) Iso-3G6′′Caf-7R (Q) Iso-3G6′′pCou-7R (R)
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