ABSTRACT
Lignin and lignans share monolignols as common precursors and are both potentially involved in plant defence against pathogens. In this study, we investigated the effects of fungal elicitors on lignin and lignan metabolism in flax (Linum usitatissimum) cell suspensions. Cell suspension cultures of flax were treated with elicitor preparations made from mycelium extracts of Botrytis cinerea, Phoma exigua and Fusarium oxysporum F ssp lini. Elicitors induced a rapid stimulation of the monolignol pathway, as confirmed by the increase in PAL (phenylalanine ammonia-lyase, EC 4.1.3.5), CCR (cinnamoyl-CoA reductase EC 1.2.1.44) and CAD (cinnamyl alcohol dehydrogenase EC 1.1.1.195) gene expression and PAL activity. At the same time, CCR activity only increased significantly in F. oxysporum-treated cells 24 h post elicitation. On the other hand, CAD activity measured for coniferyl alcohol formation was transiently decreased but a substrate-specific activation of CAD activity was observed in F. oxysporum-treated cells when using sinapyl alcohol as substrate. The accumulation of monolignol-derived products varied according to the elicitor used. B. cinerea or P. exigua-elicited cell cultures were characterised by a reinforcement of the cell wall by a deposit of 8-O-4'-linked non-condensed lignin structures and phenolic monomers, while at the same time no stimulation of 8-8'-linked lignan or 8-5'-linked phenylcoumaran lignan accumulation was observed. Additionally, elicitation of cell cultures with F. oxysporum extracts even triggered a strong incorporation of monolignols in the non condensed labile ether-linked lignin fraction concomitantly with a decrease in lignan and phenylcoumaran lignan accumulation. Several hypotheses are proposed to explain the putative role of these compounds in the defence response of flax cells against pathogens.
Subject(s)
Biological Factors/pharmacology , Coumaric Acids/metabolism , Flax/metabolism , Lignans/metabolism , Lignin/metabolism , Ascomycota/chemistry , Ascomycota/physiology , Botrytis/chemistry , Botrytis/physiology , Butylene Glycols/metabolism , Cell Wall/metabolism , Cells, Cultured , Flax/drug effects , Flax/microbiology , Fusarium/chemistry , Fusarium/physiology , Glucosides/metabolism , Lignans/biosynthesis , Mycelium/chemistry , Phenols/metabolism , Spectroscopy, Fourier Transform InfraredABSTRACT
The growth, the alkaloid production, as well as the scopolamine/hyoscyamine ratio of two clones of belladonna hairy roots were studied. The effects of nitrate and ammonium concentrations on these cultures were investigated. A rise in ammonium concentration caused the decline of the hairy roots, while nitrate had a marked effect on the alkaloid content. The alkaloid production obtained with 15.8 mM of NO3- and 20.5 mM of NH4+ was 1.2-1.4 times higher than that obtained when the roots were grown in the standard Murashige and Skoog medium (MS medium, 39.5 mM of NO3- and 20.5 mM of NH4+). The nitrate and ammonium concentrations in the culture medium also had a strong influence on the scopolamine/hyoscyamine ratio. When nitrate or ammonium concentrations were raised, that ratio also was increased 2-3-fold. The hairy root clones originating from transformations with two distinct strains of Agrobacterium had similar responses.
Subject(s)
Atropa belladonna/growth & development , Atropa belladonna/metabolism , Belladonna Alkaloids/metabolism , Nitrates/metabolism , Plant Roots/growth & development , Plant Roots/metabolism , Plants, Medicinal , Plants, Toxic , Quaternary Ammonium Compounds/metabolism , Atropa belladonna/chemistry , Atropine Derivatives/metabolism , Belladonna Alkaloids/chemistry , Chromatography, High Pressure Liquid , Nitrates/chemistry , Plant Roots/chemistry , Quaternary Ammonium Compounds/chemistry , Scopolamine/metabolismABSTRACT
Transformed callus cultures of Nicotiana tabacum were generated in which the SAM-1 gene from Arabidopsis thaliana encoding S-adenosylmethionine synthetase (SAM-S), under the control of the 35S promoter, had been integrated. The presence of the SAM-1 gene was detected in all tested transformants and the SAM-S activity correlated with the accumulation of SAM in the tobacco callus cultures. Three distinct phenotypic classes were identified among the transgenic cell lines in relation to growth of the cells, structure of the calli, and level of SAM. Transgene silencing was observed in several cultivated transgenic calli and this phenomenon was correlated directly with a low level of SAM-1 mRNA accompanied by a decrease of the SAM-S activity. The transgenic calli overexpressing the SAM-1 gene accumulated a high SAM level. The modifications in SAM-S activity were reflected in the pattern of secondary products present in the different cell lines, thereby demonstrating that the flux through the biosynthetic pathway of a plant secondary product can be modified by means of genetic engineering.
