The glucosinolate transporters 1/2/3 (GTR1/2/3) from the Nitrate and Peptide transporter Family (NPF) play an essential role in the transport, accumulation, and distribution of the specialized plant metabolite glucosinolates. Due to representing both antinutritional and health-promoting compounds, there is increasing interest in characterizing GTRs from various plant species. We generated seven artificial glucosinolates (either aliphatic or benzenic) bearing different fluorophores (Fluorescein, BODIPY, Rhodamine, Dansylamide, and NBD) and investigated the ability of GTR1/2/3 from Arabidopsis thaliana to import the fluorescent glucosinolates (F-GSLs) into oocytes from Xenopus laevis. Five out of the seven F-GSLs synthesized were imported by at least one of the GTRs. GTR1 and GTR2 were able to import three F-GSLs actively above external concentration, while GTR3 imported only one actively. Competition assays indicate that the F-GSLs are transported by the same mechanism as non-tagged natural glucosinolates. The GTR-mediated F-GSL uptake is detected via a rapid and sensitive assay only requiring simple fluorescence measurements on a standard plate reader. This is highly useful in investigations of glucosinolate transport function and provides a critical prerequisite for elucidating the relationship between structure and function through high-throughput screening of GTR mutant libraries. The F-GSL themselves may also be suitable for future studies on glucosinolate transport in vivo.

Glucosinolates (GSLs) are a unique class of thioglucosides that evolved as defense mechanisms in the 16 families of the Brassicales order and present molecular tags which can be placed in a robust phylogenetic framework through investigations into their evolution and diversity. The GSL profiles of three Resedaceae species, Reseda alba, R. lutea, and R. phyteuma, were examined qualitatively and quantitatively with respect to their desulfo-counterparts utilizing UHPLC-DAD-MS/MS. In addition, NMR analysis of isolated 2-hydroxy-2-methylpropyl desulfoGSL (d31) was performed. Three Phe-derived GSLs were found in R. lutea, including glucotropaeolin (11) (0.6–106.69 mol g−1 DW), 2-(α-L-ramnopyranosyloxy)benzyl GSL (109) (8.10–57.89 μmol g−1 DW), glucolepigramin (22) (8.66 μmol g−1 DW in flower), and Trp-derived glucobrassicin (43) (0.76–5.92 μmol g−1 DW). The Phe-derived GSLs 109 (50.79–164.37 μmol g−1 DW), gluconasturtiin (105) (1.97 μmol g−1 DW), and 11 (tr), as well as the Trp-derived GSL glucobrassicin (43) (3.13–11.26 μmol g−1 DW), were all present in R. phyteuma. R. alba also contained Phe-derived 105 (0.10–107.77 μmol g−1 DW), followed by Trp-derived 43 (0.85–3.50 μmol g−1 DW) and neoglucobrassicin (47) (0.23–2.74 μmol g−1 DW). However, regarding the GSLs in R. alba, which originated from Leu biosynthesis, 31 was the major GSL (6.48 to 52.72 μmol g−1 DW) and isobutyl GSL (62) was the minor GSL (0.13 to 1.13 μmol g−1 DW). The discovered Reseda profiles, along with new evidence provided by GSL characterizations, were studied in the context of the current knowledge on GLSs in the Resedaceae family. With the exception of R. alba, the aliphatic GSLs of which were outliers among the Resedaceae species studied, this family typically contains GSLs derived primarily from Trp and Phe biosynthesis, which modifications resulted in GSLs unique to this family, implying presence of the specific genes. responsible for this diversification.

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