In this report, we have investigated the influence of different light qualities on Digitalis purpurea under a controlled environment. For this purpose, red (R), blue (B), fluorescent lamp (FL, ...control), along with combined red and blue (R:B) LEDs were used. Interestingly, the plant growth parameters such as number of leaf, longest root, width of leaf, width of stomata, width of trichome, leaf area, leaf or root fresh weight (FW), weight (DW) as well as length of trichome were maximum under R:B (8:2), and significantly larger than control plants. The stomatal conductance or anthocyanin was maximum under B LED than those under FL, however the photosynthesis rate was greater under FL. RuBisCO activity was maximum under R:B (1:1) LEDs while the quantity of the UV absorbing substances was highest under R LED than under FL. The maximum amount of cardenolides were obtained from leaf tissue under R:B (2:8) LED than those under FL. The R:B LEDs light was suitable for Digitalis plant growth, development, micro- and macro-elements, as well as cardenolides accumulation in the plant factory system. The adaptation of the growth strategy developed in this study would be useful for the production of optimized secondary metabolites in Digitalis spp.
This review provides a renewed look at the genus
. Emphasis will be put on those issues that attracted the most attention or even went through paradigmatic changes since the turn of the millennium. ...PubMed and Google Scholar were used ("
" and "Foxglove" were the key words) to identify research from 2000 till 2017 containing data relevant enough to be presented here. Intriguing new results emerged from studies related to the phylogeny and taxonomy of the genus as well as to the biosynthesis and potential medicinal uses of the key active compounds, the cardiac glycosides. Several Eastern and Western Foxgloves were studied with respect to their propagation
In this context, molecular biology tools were applied and phytochemical analyses were conducted. Structure elucidation and analytical methods, which have experienced less exciting progress, will not be considered here in great detail.
Abstract
Cardenolides are steroidal metabolites in Digitalis lanata with potent cardioactive effects on animals. In plants, cardenolides are likely involved in various stress responses. However, the ...molecular mechanism of cardenolide increase during stresses is mostly unknown. Additionally, cardenolides are proposed to arise from cholesterol, but indirect results show that phytosterols may also be substrates for cardenolide biosynthesis. Here, we show that cardenolides increased after methyl jasmonate (MJ), sorbitol, potassium chloride (KCl) and salicylic acid analog 2,1,3-benzothiadiazole (BTH) treatments. However, the expression of three known genes for cardenolide biosynthesis did not correlate well with these increases. Specifically, the expression of progesterone-5β-reductases (P5βR and P5βR2) did not correlate with the cardenolide increase. The expression of 3β-hydroxysteroid dehydrogenase (3βHSD) correlated with changes in cardenolide levels only during the BTH treatment. Mining the D. lanata transcriptome identified genes involved in cholesterol and phytosterol biosynthesis: C24 sterol sidechain reductase 1 (SSR1), C4 sterol methyl oxidase 1, and 3 (SMO1 and SMO3). Surprisingly, the expression of all three genes correlated well with the cardenolide increase after the BTH treatment. Phylogenetic analysis showed that SSR1 is likely involved in both cholesterol and phytosterol biosynthesis. In addition, SMO1 is likely specific to phytosterol biosynthesis, and SMO3 is specific to cholesterol biosynthesis. These results suggest that stress-induced increase of cardenolides in foxglove may correlate with cholesterol and phytosterol biosynthesis. In summary, this work shows that cardenolides are important for stress responses in D. lanata and reveals a potential link between phytosterol and cardenolide biosynthesis.
Key message
Studying RNAi-mediated
DlP5βR1
and
DlP5βR2
knockdown shoot culture lines of
Digitalis lanata,
we here provide direct evidence for the participation of PRISEs (progesterone ...5β-reductase/iridoid synthase-like enzymes) in 5β-cardenolide formation.
Progesterone 5β-reductases (P5βR) are assumed to catalyze the reduction of progesterone to 5β-pregnane-3,20-dione, which is a crucial step in the biosynthesis of the 5β-cardenolides. P5βRs are encoded by
VEP
1-like genes occurring ubiquitously in embryophytes. P5βRs are substrate-promiscuous enone-1,4-reductases recently termed PRISEs (progesterone 5β-reductase/iridoid synthase-like enzymes). Two PRISE genes, termed
DlP5βR1
(AY585867.1) and
DlP5βR2
(HM210089.1) were isolated from
Digitalis lanata
. To give experimental evidence for the participation of PRISEs in 5β-cardenolide formation, we here established several RNAi-mediated
DlP5βR1
and
DlP5βR2
knockdown shoot culture lines of
D. lanata
. Cardenolide contents were lower in
D. lanata P5βR-RNAi
lines than in wild-type shoots. We considered that the gene knockdowns may have had pleiotropic effects such as an increase in glutathione (GSH) which is known to inhibit cardenolide formation. GSH levels and expression of glutathione reductase (GR) were measured. Both were higher in the
Dl P5βR-RNAi
lines than in the wild-type shoots. Cardenolide biosynthesis was restored by buthionine sulfoximine (BSO) treatment in
Dl P5βR2-RNAi
lines but not in
Dl P5βR1-RNAi
lines. Since progesterone is a precursor of cardenolides but can also act as a reactive electrophile species (RES), we here discriminated between these by comparing the effects of progesterone and methyl vinyl ketone, a small RES but not a precursor of cardenolides. To the best of our knowledge, we here demonstrated for the first time that
P5βR1
is involved in cardenolide formation. We also provide further evidence that PRISEs are also important for plants dealing with stress by detoxifying reactive electrophile species (RES).
Je donnerai ici des pistes pour construire une séquence d’enseignement/apprentissage à partir d’un exemple concret, fourni par une peinture sur vase (images 1 et 2) et par deux courts extraits de ...textes littéraires en langue originale (1a et 2a) : leur avantage est d’illustrer d’une manière synthétique et efficace un imaginaire héroïque ancré dans la mémoire culturelle des Grecs. En l’occurrence, j’ai sélectionné un moment particulier de la chute de Troie en m’appuyant sur deux monographies scientifiques (Anderson 1997 et Mangold 2006). L’objectif de la séquence est d’amener les élèves à reconstruire ce moment à travers une lecture contextualisée de l’image et des textes, ainsi qu’à comprendre et à mémoriser les points forts de cet imaginaire : des détails figuratifs susceptibles d’illustrer le champ sémantique de certains mots grecs.
Elimination of calcium (Ca), magnesium (Mg) or both from the medium of callus cultures of Digitalis davisiana Heywood, Digitalis lamarckii Ivanina, Digitalis trojana Ivanina and Digitalis cariensis ...Boiss. ex Jaub. et Spach increased cardenolides production. Callus was induced from hypocotyl segments from one-month old seedlings were cultured on MS medium containing 0.5 μg ml−1 thidiazuron (TDZ) and 0.25 μg ml−1 indole acetic acid (IAA). After 30 days of culture, callus was transferred in hormone-free MS medium (MSO) as well as Ca or Mg or both were completely eliminated from same medium. The amount of five cardenolides from D. davisiana Heywood, D. lamarckii Ivanina, D. trojana Ivanina and D. cariensis Boiss. ex Jaub. et Spach were compared. Higher amounts of five cardenolides and total cardenolides were obtained when callus of four Digitalis species were incubated on MS medium lacking both Ca and Mg. The mean contents of total cardenolides obtained were in the order of D. lamarckii (2017.97 μg g−1) > D. trojana (1385.75 μg g−1) > D. cariensis (1038.65 μg g−1) > D. davisiana (899.86 μg g−1) when both Ca and Mg were eliminated from the medium, respectively. This protocol is useful for development of new strategies for the large-scale production of cardenolides.
•HPLC analysis revealed that all stress conditions were significantly effective.•The predominant cardiac glycoside was lanatoside C.•No digoxin was detected in all treatments.•Deficiency of both Ca and Mg resulted in the highest level of cardiac glycosides.
Digitalis purpurea
L. (Scrophulariaceae; Foxglove) is a source of cardiotonic glycosides such as digitoxin and digoxin which are commercially applied in the treatment to strengthen cardiac diffusion ...and to regulate heart rhythm. This investigation deals with in vitro propagation and elicited production of cardiotonic glycosides digitoxin and digoxin in shoot cultures of
D
.
purpurea
L. In vitro germinated seedlings were used as a primary source of explants. Multiple shoot formation was achieved for three explant types (nodal, internodal, and leaf) cultured on Murashige and Skoog (MS) medium with several treatments of cytokinins (6-benzyladenine—BA; kinetin—Kin; and thidiazuron—TDZ) and auxins (indole-3-acetic acid—IAA; α-naphthaleneacetic acid—NAA; and 2,4-dichlorophenoxy acetic acid—2,4-D). Maximum multiple shoots (12.7 ± 0.6) were produced from nodal explants on MS + 7.5 μM BA. Shoots were rooted in vitro on MS containing 15 μM IAA. Rooted plantlets were successfully acclimatized. To further maintain the multiple shoot induction, mother tissue was cut into four equal parts and repeatedly sub-cultured on fresh shoot induction liquid medium after each harvest. On adaptation of this strategy, an average of 18 shoots per explant could be produced. This strategy was applied for the production of biomass and glycosides digitoxin and digoxin in shoot cultures on MS medium supplemented with 7.5 μM BA and several treatments with plant growth regulators, incubation period, abiotic (salicylic acid, mannitol, sorbitol, PEG-6000, NaCl, and KCl), biotic (
Aspergillus niger
,
Helminthosporium
sp.,
Alternaria
sp., chitin, and yeast extract) elicitors, and precursors (progesterone, cholesterol, and squalene). The treatment of KCl, mycelial mass of
Helminthosporium
sp., and progesterone were highly effective for the production of cardenolides. In the presence of progesterone (200 to 300 mg/l), digitoxin and digoxin accumulation was enhanced by 9.1- and 11.9-folds respectively.
Long periods of high temperature or transitory increased temperature, a widespread agricultural problem, may lead to a drastic reduction in economic yield, affecting plant growth and development in ...many areas of the world. Heat stress causes many anatomical and physiological changes in plants. Its unfavorable effects can be alleviated by thermotolerance induced by exogenous application of plant growth regulators and osmoprotectants or by gradual application of temperature stress. Digitalis trojana Ivanina is an important medicinal plant species well known mainly for its cardenolides. The production of cardenolides via traditional agriculture is commercially inadequate. In this study, elicitation strategies were employed for improving crop thermotolerance and accumulation of cardenolides. For these purposes, the effects of salicylic acid (SA) and/or high temperature treatments in inducing cardenolide accumulation and thermotolerance were tested in callus cultures of D. trojana. Considerable increases in the production of cardenolides (up to 472.28 μg.g−1 dry weight, dw) and induction of thermotolerance capacity were observed when callus cultures were exposed to high temperature for 2 h after pretreating with SA. High temperature treatments (2 h and 4 h) caused a marked reduction in superoxide dismutase (SOD; EC 1.15.1.1) and catalase (CAT; EC 1.11.1.6) activities, while SA pretreatment increased their activities. High temperature and/or SA appeared to increase the levels of proline, total phenolic, and flavonoid content. Elevated phenolic accumulation could be associated with increased stress protection. These results indicated that SA treatments induced synthesis of antioxidants and cardenolides, which may play a significant role in resistance to high temperature stress.
•SA alleviates inhibitory effects of heat stress.•SA induces thermotolerance and cardenolide accumulation in Digitalis trojana.•SA activated antioxidant responses in D. trojana.
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