Production of pyrrolizidine alkaloids and shikonins in Echium plantagineum L. in response to various plant stressors

Abstract

Background Echium plantagineum, a native of Europe and Africa, is a noxious invasive weed in Australia forming monocultural stands in pastures and rangelands. It produces a complex mixture of bioactive secondary metabolites, including toxic pyrrolizidine alkaloids (PAs), that protect the plant from insect and livestock herbivory and naphthoquinones (NQs), which suppress competition from weeds, insects and pathogens, and also influence invasion success. However, the extent to which allelochemical production is impacted by environmental factors, thereby influencing plant defense against pests, remains unclear. Results Following plant stress induced by drought, herbivory and high temperature, extracts of E. plantagineum shoots and roots were subjected to metabolic profiling by UPLC‐MS‐DAD‐ QToF mass spectrometry. Abundance of NQs, especially deoxyshikonin, shikonin and dimethylacrylshikonin, rapidly increased in roots exposed to elevated temperatures. Water withholding initially increased NQ abundance, but prolonged drought resulted in reduced total PAs and NQs. Intraspecific competition elevated the production of NQs, whereas simulated herbivory had no initial effect on NQs. Following herbivory, the abundance of the PA 3′‐O‐acetylechimidine‐N‐oxide in seedling shoots was increased. Conclusions Differential accumulation of defense metabolites by E. plantagineum following exposure to various stressors suggested stress‐dependent biosynthetic regulation, particularly with respect to NQ production, which was rapidly induced following drought, intraspecific competition and high temperature treatment, thereby positively impacting resistance or defense against herbivores, weeds and pathogens. We propose that trade‐offs between above‐ and below‐ground metabolism in E. plantagineum may facilitate allelochemical production in response to stress, rendering plants with an enhanced ability to defend against other neighboring plants, insects and microbes, with allelochemical production further facilitated by catabolic recycling following lengthier exposure to stress. © 2019 Society of Chemical Industry

Metabolic Toxification of 1,2-Unsaturated Pyrrolizidine Alkaloids Causes Human Hepatic Sinusoidal Obstruction Syndrome: The Update

“…Second, PA synthesis is dependent on developmental stage and thus on the season of harvest, shown in a study from Italy presenting an average PA content of plants of 0.33% of dry weight over the growing season, in which the highest PA levels, of around 1%, were found in the young sprouts and flower heads [ 164 ], whereas another study showed increased total amounts of PAs during plant development, correlating with an increase in biomass at nearly constant PA concentrations [ 39 ]. More specifically, the highest PA concentrations ranged from 3.2 to 6.6 g/kg dry weight and were found in plants from the beginning of July until the middle of October when the rainy season begins [ 165 ], findings that are in line with increased PA concentrations in plants under drought conditions [ 166 , 167 ]. PA production in plants was reduced under the use of nutrients such as NBK (nitrogen, phosphorus, and potassium) fertilizers, which are complete fertilizers [ 168 ].…”

Root-associated bacteria modulate the specialised metabolome of Lithospermum officinale L.

“…Recent studies were performed to elucidate the shikonin production pathway and its regulation in planta . For example, Skoneczny et al (2019) used a metabolomic approach, profiling naphthoquinones and pyrrolizidine alkaloids and demonstrated the influence of high temperature and water withholding on the accumulation of A/Sd, especially deoxyshikonin, in Echium plantagineum . Similarly, shikonin derivatives were shown to accumulate over time in Echium spp.…”

Novel chemicals engender myriad invasion mechanisms

“…This article is protected by copyright. All rights reserved variation in soil nutrients (Effah et al, 2020) Chromolaena odorata Odoratin Higher amounts of odoratin in non- (Tharayil et al, 2009) Datura stramonium (native Atropine and scopolamine Greater amounts of two compounds in to Mexico; invasive in Spain) native range than in non-native range owing to presence of specialist herbivores (Castillo et al, 2019) Echium plantagineum Naphthoquinones and Defend against insect and (native to Europe and Asia; pyrrolizidine alkaloids livestock herbivory, competitive invasive in Australia) advantages against weeds (Skoneczny et al, 2019).…”