Abstract
Benzoxazinoids (BXs) are specialized metabolites with protective properties that are synthesized predominantly by Poaceae species, including rye (Secale cereale). Among factors known to influence BXs production, prolonged low temperature has not been studied previously. In this study, the influence of cultivation at 4 °C, which is essential for vernalization, on the concentration of BXs (HBOA, DIBOA, GDIBOA, DIMBOA, GDIMBOA, and MBOA) and the expression level of genes involved in the BX biosynthesis pathway (ScBx1–ScBx5 and ScIgl) in three rye inbred lines was investigated. After cultivation for seven weeks at 4 °C, the expression level of all analyzed genes and BX concentrations had decreased compared with those at the initiation of treatment (21 days after germination) in control and cold-treated plants. At this time point, the decrease in BX concentrations and gene expression was lower in cold-treated plants than in untreated plants. In contrast, at 77 days after germination, the gene expression levels and BX concentrations in untreated plants had generally increased. Investigation of the vernalization impact on rye BXs accumulation, as well as on Bx gene expression, may aid with determination of the most suitable winter lines and cultivars of rye for cultivation and breeding purposes.
Highlights
Benzoxazinoids (BXs) are specialized metabolites and an important element of the defense mechanism against biotic and abiotic stresses in plant species predominantly belonging to the Poaceae.BXs play an important role in allelopathy [1,2,3,4]
The lines were selected based on the distinct BX concentrations measured after a natural vernalization period; line L318 was characterized by the highest, line D33 by the intermediate, and line D39 by the lowest concentration of DIBOA and the sum of BXs [48] (Supplementary Materials, Table S1)
After seven weeks of cultivation, under both 4 ◦ C and the control temperature, the expression level of all analyzed genes, except that of ScIgl in lines L318 and D33, decreased compared with that observed at the first time point (Figure 1, Table 2)
Summary
Benzoxazinoids (BXs) are specialized metabolites and an important element of the defense mechanism against biotic and abiotic stresses in plant species predominantly belonging to the Poaceae. BXs play an important role in allelopathy [1,2,3,4]. BXs can influence other plant processes such as flowering time, auxin metabolism, iron uptake, and aluminum tolerance [5]. Four consecutive cytochrome P450 monooxygenases convert indole to 2,4-dihydroxy-2H-1,4-benzoxazin-3(4H)-one (DIBOA) [6,7,8]. 2-oxoglutarate-dependent dioxygenase and 7-O-methyltransferase are responsible for DIBOA glucoside (DIBOA-Glc; GDIBOA) transformation to 4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one glucoside (DIMBOA-Glc; GDIMBOA) (Figure S1) [9,10]. To protect the cell from toxic aglucons, glucosyltransferases transform the aglucons into harmless, stable compounds of increased solubility, which enable their storage in vacuoles [11,12]
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