TY - JOUR

T1 - Phytoalexins of the crucifer Barbarea vulgaris

T2 - Structural profile and correlation with glucosinolate turnover

AU - Cárdenas, Pablo D.

AU - Landtved, Jonas P.

AU - Larsen, Signe H.

AU - Lindegaard, Nicolai

AU - Wøhlk, Sebastian

AU - Jensen, Karen R.

AU - Pattison, David I.

AU - Burow, Meike

AU - Bak, Søren

AU - Crocoll, Christoph

AU - Agerbirk, Niels

N1 - Funding Information: We thank Prof. M.S.C. Pedras for generously sharing standards and suggestions, including detailed comments to earlier versions of the manuscript, MSc E. Ciepiel for assisting with biological experiments, Dr. T. Yang for carrying out chiral HPLC of kjaerin, Dr. T.P. Hauser for constructive discussions, Torben og Alice Frimodts Fond for financial support, and three anonymous reviewers for constructive comments which improved the manuscript. Publisher Copyright: © 2023 The Authors

PY - 2023

Y1 - 2023

N2 - Phytoalexins are antimicrobial plant metabolites elicited by microbial attack or abiotic stress. We investigated phytoalexin profiles after foliar abiotic elicitation in the crucifer Barbarea vulgaris and interactions with the glucosinolate-myrosinase system. The treatment for abiotic elicitation was a foliar spray with CuCl2 solution, a usual eliciting agent, and three independent experiments were carried out. Two genotypes of B. vulgaris (G-type and P-type) accumulated the same three major phytoalexins in rosette leaves after treatment: phenyl-containing nasturlexin D and indole-containing cyclonasturlexin and cyclobrassinin. Phytoalexin levels were investigated daily by UHPLC-QToF MS and tended to differ among plant types and individual phytoalexins. In roots, phytoalexins were low or not detected. In treated leaves, typical total phytoalexin levels were in the range 1–10 nmol/g fresh wt. during three days after treatment while typical total glucosinolate (GSL) levels were three orders of magnitude higher. Levels of some minor GSLs responded to the treatment: phenethylGSL (PE) and 4-substituted indole GSLs. Levels of PE, a suggested nasturlexin D precursor, were lower in treated plants than controls. Another suggested precursor GSL, 3-hydroxyPE, was not detected, suggesting PE hydrolysis to be a key biosynthetic step. Levels of 4-substituted indole GSLs differed markedly between treated and control plants in most experiments, but not in a consistent way. The dominant GSLs, glucobarbarins, are not believed to be phytoalexin precursors. We observed statistically significant linear correlations between total major phytoalexins and the glucobarbarin products barbarin and resedine, suggesting that GSL turnover for phytoalexin biosynthesis was unspecific. In contrast, we did not find correlations between total major phytoalexins and raphanusamic acid or total glucobarbarins and barbarin. In conclusion, two groups of phytoalexins were detected in B. vulgaris, apparently derived from the GSLs PE and indol-3-ylmethylGSL. Phytoalexin biosynthesis was accompanied by depletion of the precursor PE and by turnover of major non-precursor GSLs to resedine. This work paves the way for identifying and characterizing genes and enzymes in the biosyntheses of phytoalexins and resedine.

AB - Phytoalexins are antimicrobial plant metabolites elicited by microbial attack or abiotic stress. We investigated phytoalexin profiles after foliar abiotic elicitation in the crucifer Barbarea vulgaris and interactions with the glucosinolate-myrosinase system. The treatment for abiotic elicitation was a foliar spray with CuCl2 solution, a usual eliciting agent, and three independent experiments were carried out. Two genotypes of B. vulgaris (G-type and P-type) accumulated the same three major phytoalexins in rosette leaves after treatment: phenyl-containing nasturlexin D and indole-containing cyclonasturlexin and cyclobrassinin. Phytoalexin levels were investigated daily by UHPLC-QToF MS and tended to differ among plant types and individual phytoalexins. In roots, phytoalexins were low or not detected. In treated leaves, typical total phytoalexin levels were in the range 1–10 nmol/g fresh wt. during three days after treatment while typical total glucosinolate (GSL) levels were three orders of magnitude higher. Levels of some minor GSLs responded to the treatment: phenethylGSL (PE) and 4-substituted indole GSLs. Levels of PE, a suggested nasturlexin D precursor, were lower in treated plants than controls. Another suggested precursor GSL, 3-hydroxyPE, was not detected, suggesting PE hydrolysis to be a key biosynthetic step. Levels of 4-substituted indole GSLs differed markedly between treated and control plants in most experiments, but not in a consistent way. The dominant GSLs, glucobarbarins, are not believed to be phytoalexin precursors. We observed statistically significant linear correlations between total major phytoalexins and the glucobarbarin products barbarin and resedine, suggesting that GSL turnover for phytoalexin biosynthesis was unspecific. In contrast, we did not find correlations between total major phytoalexins and raphanusamic acid or total glucobarbarins and barbarin. In conclusion, two groups of phytoalexins were detected in B. vulgaris, apparently derived from the GSLs PE and indol-3-ylmethylGSL. Phytoalexin biosynthesis was accompanied by depletion of the precursor PE and by turnover of major non-precursor GSLs to resedine. This work paves the way for identifying and characterizing genes and enzymes in the biosyntheses of phytoalexins and resedine.

KW - 2-Phenylethylglucosinolate

KW - Aromatic glucosinolates

KW - Benzenic glucosinolates

KW - Brassicaceae

KW - Copper chloride

KW - Elicitation

KW - Gluconasturtiin

KW - Glucosinolate hydrolysis

KW - Indole glucosinolates

KW - Indole phytoalexins

KW - Induction

KW - Myrosinase

KW - Phytoalexin biosynthesis

KW - Tribe cardamineae

U2 - 10.1016/j.phytochem.2023.113742

DO - 10.1016/j.phytochem.2023.113742

M3 - Journal article

C2 - 37269935

AN - SCOPUS:85161698023

VL - 213

JO - Phytochemistry

JF - Phytochemistry

SN - 0031-9422

M1 - 113742

ER -