Chemical genetic interrogation of natural variation uncovers a molecule that is glycoactivated

Abstract

Natural variation in human drug metabolism and target genes can cause pharmacogenetic or interindividual variation in drug sensitivity. We reasoned that natural pharmacogenetic variation in model organisms could be systematically exploited to facilitate the characterization of new small molecules. To test this, we subjected multiple Arabidopsis thaliana accessions to chemical genetic screens and discovered 12 accession-selective hit molecules. As a model for understanding this variation, we characterized natural resistance to hypostatin, a new inhibitor of cell expansion. Map-based cloning identified HYR1, a UDP glycosyltransferase (UGT), as causative for hypostatin resistance. Multiple lines of evidence demonstrate that HYR1 glucosylates hypostatin in vivo to form a bioactive glucoside. Additionally, we delineated a HYR1 substrate motif and used it to identify another molecule modulated by glucosylation. Our results demonstrate that natural variation can be exploited to inform the biology of new small molecules, and that UGT sequence variation affects xenobiotic sensitivity across biological kingdoms.

Activation of dimeric ABA receptors elicits guard cell closure, ABA-regulated gene expression, and drought tolerance

“…Chemical metabolism, uptake, transport, and target sites can vary between plant species, and consequently, many bioactive compounds can show species-or genotype-specific effects (37). We therefore examined the expression of ABA responsive genes after quinabactin applications to soybean, barley, and maize, diverse agricultural species that span the monocot-dicot split.…”

Potent and selective activation of abscisic acid receptors in vivo by mutational stabilization of their agonist-bound conformation

“…ABA can normally activate a multiplicity of receptors in the wild-type context, and it is not yet clear if different receptors have different subfunctions. To date, selective ABA receptor activation has only been achieved using pyrabactin (1,29), which has strong agonist activity on PYR1 and PYL1 and activates a full complement of ABA-responsive gene transcription in imbibed seeds. The genetic removal of PYR1, but not PYL1, causes pyrabactin insensitivity during germination, which argues that the major cellular target of pyrabactin in seeds is PYR1 and that activating PYR1 is sufficient to activate seed ABA signaling.…”

Molecular and functional characterization of novel furofuran-class lignan glucosyltransferases from Forsythia

“…Nevertheless, the structural diversity of lignan glycosides strongly suggests that not all lignan UGTs belong to the UGT71 family since flavonoid UGTs form separate phylogenetic clades based on their various regio-specificities (Noguchi et al 2009). It was previously reported that Sesamum UGT71A9 participates in the glucosylation of an intrinsic furofuran lignan, sesaminol, while other UGT71 enzymes are involved in the glucosylation of the flavonoid/triterpene (Medicago UGT71G1), a growth inhibitor (Arabidopsis UGT71B2/HYR1), exogenous naphthols (Nicotiana UGT71A6,7,11), exogenous curcumin (Catharanthus UGT71E2), and endogenous phytohormone (Arabidopsis UGT71B6) (Kaminaga et al 2004;Noguchi et al 2008;Priest et al 2006;Taguchi et al 2003;Zhao et al 2007), so the target compounds of the UGT71 enzymes are evidently structurally diverse (Figure 3). In addition to these reports, the present results support the view that the UGT71 family enzymes possess promiscuous substrate specificity, and some of them have adapted to lignans.…”