Elicitation of Jerusalem artichoke (Helianthus tuberosus L.) cell suspension culture for enhancement of inulin production and altered degree of polymerisation

Occurrence, Distribution, and Transmission of Alfalfa Viruses in China

Alfalfa (Medicago sativa L.) is one of the most important quality forages worldwide and is cultivated throughout China. Alfalfa is susceptible to a variety of viral diseases during its growth, which has caused huge amounts of commercial losses. However, the profile of the alfalfa virus in China remains ambiguous and the viruses transmitted by Odontothrips loti (Haliday), dominant insect pests in alfalfa, are also poorly understood. In the present study, virus diversity was investigated in the primary alfalfa-growing areas in China. A total of 18 alfalfa viruses were identified through RNA-sequencing (RNA-seq) and reverse transcription-polymerase chain reaction (RT-PCR). Two new plant viruses, Medicago sativa virus 1 (MsV1) and Medicago sativa luteovirus 1 (MsLV1), were detected for the first time. Another four viruses, including the Alfalfa ringspot-associated virus (ARaV), Alfalfa virus F (AVF), Alfalfa enamovirus 1 (AEV1), and Alfalfa deltaparitivirus (ADPV), were reported in China for the first time as well. Both Alfalfa mosaic virus (AMV) and Medicago sativa alphapartitivirus 2 (MsAPV2) are the dominant pathogens, with an infection incidence of 91.7-100%, and 74.4-97.2%, respectively. Additionally, O. loti with first- and second-instar nymphs were shown to acquire the AMV within 0.25 h of feeding on a virus-infected alfalfa. Transmission by thrips to healthy alfalfa plants was also demonstrated. Additionally, we clarified the dynamic changes in the AMV in pre-adult stages of O. loti, which indicated that the AMV is propagated in the nymph stage of O. loti. These findings provide valuable information for understanding the alfalfa virome, confirm the role thrips O. loti plays in alfalfa virus transmission, and improve our fundamental knowledge and management of diseases in China.

Arnica montana Cell Culture Establishment, and Assessment of Its Cytotoxic, Antibacterial, α-Amylase Inhibitor, and Antioxidant In Vitro Bioactivities

Arnica montana cell suspension culture could be a sustainable source of a vegetal material producer of secondary metabolites (SMs) possessing biological effects. Different plant growth regulator concentrations (0-5 mg/L) were tested in foliar explants to induce a callus that was used to establish a cell suspension culture. Growth kinetics was carried out for 30 days. A methanolic extract obtained from biomass harvested at 30 days of growth kinetics was fractionated, and three fractions were tested for bioactivities. We induced a callus with 1 mg/L of picloram and 0.5 mg/L of kinetin in foliar explants, which allowed for the establishment of a cell suspension culture, and the latter had the highest total SMs contents at day 30. Three fractions showed differences in total SMs contents, with the highest values per gram as follows: 270 mg gallic acid equivalent for total phenolic content, 200 mg quercetin equivalent for total flavonoid content, 83 mg verbascoside equivalent for total phenolic acid content, and 396 mg parthenolide equivalent for total sesquiterpene lactone content. The best bioactivities were 2-6 µg/mL for the 50% inhibition of 2,2-diphenyl-1-picrylhydrazyl radical, 30% cellular viability of lymphoma cells at 40 µg/mL, 17% inhibition against Escherichia coli and Staphylococcus aureus at 8 µg/disk, and α-amylase inhibition at 12% with 10 µg/mL. The total SMs contents were correlated with bioactivities.

Improvement and prediction of secondary metabolites production under yeast extract elicitation of Azadirachta indica cell suspension culture using response surface methodology

Neem is a medicinal plant used as antimalarial, antibacterial, antiviral, insecticide, and antimicrobial drug. This study aimed to investigate and predict the effect of yeast extract and sampling time on cell growth, secondary metabolites synthesis, SQS1 and MOF1 genes expression by response surface methodology. The highest fresh and dry cell weights were 580.25 g/L and 21.01 g/L, respectively obtained 6 days after using 100 mg/L yeast extract. The highest azadirachtin accumulation and production were 16.08 mg/g DW and 219.78 mg/L obtained 2 and 4 days, respectively after using 25 mg/L yeast extract. Maximum mevalonic acid accumulation (1.75 mg/g DW) and production (23.77 mg/L) were observed 2 days after application of 50 mg/L yeast extract. The highest amount of squalene accumulation (0.22 mg/g DW) and production (4.53 mg/L) were achieved 4 days after using 50 mg/L yeast extract. Prediction results exhibited the highest azadirachtin accumulation (13.61 mg/g DW) and production (190.50 mg/L), mevalonic acid accumulation (0.50 mg/g DW) and production (5.57 mg/L), and squalene accumulation (0.30 mg/g DW) by using 245 mg/L yeast extract for 2 days, 71 mg/L yeast extract for 2 days, 200 mg/L yeast extract for 4.96 days, without yeast extract for 6.54 days and 4 days, respectively. Also, it was predicted that the highest squalene production is achieved by long-term exposure to high concentrations of yeast extract. The qRT-PCR analysis displayed the maximum relative gene expression of SQS1 and MOF1 by using 150 and 25 mg/L yeast extract for 4 and 2 days treatment.

Extraction and Characterization of Inulin-Type Fructans from Artichoke Wastes and Their Effect on the Growth of Intestinal Bacteria Associated with Health

Globe artichoke is an intriguing source of indigestible sugar polymers such as inulin-type fructans. In this study, the effect of ultrasound in combination with ethanol precipitation to enhance the extraction of long chain fructans from artichoke wastes has been evaluated. The inulin-type fructans content both from bracts and stems was measured using an enzymatic fructanase-based assay, while its average degree of polymerization (DP) was determined by HPLC-RID analysis. Results show that this method provides artichoke extracts with an inulin-type fructans content of 70% with an average DP between 32 and 42 both in bracts and in stems. The prebiotic effect of long chain inulins from artichoke extract wastes was demonstrated by its ability to support the growth of five Lactobacillus and four Bifidobacterium species, previously characterized as probiotics. Besides, we considered the possibility to industrialize the process developing a simpler method for the production of inulin-type fructans from the artichoke wastes so that the artichoke inulin preparation could be suitable for its use in synbiotic formulations in combination with different probiotics for further studies including in vivo trials.

The genus Portulaca as a suitable model to study the mechanisms of plant tolerance to drought and salinity

Drought and soil salinity are at present the major factors responsible for the global reduction of crop yields, and the problem will become more severe in the coming decades because of climate change effects. The most promising strategy to achieve the increased agricultural production that will be required to meet food demands worldwide will be based on the enhancement of crop stress tolerance, by both, traditional breeding and genetic engineering. This, in turn, requires a deep understanding of the mechanisms of tolerance which, although based on a conserved set of basic responses, vary widely among plant species. Therefore, the use of different plant models to investigate these mechanisms appears to be a sensible approach. The genus Portulaca could be a suitable model to carry out these studies, as some of its taxa have been described as tolerant to drought and/or salinity. Information on relevant mechanisms of tolerance to salt and water stress can be obtained by correlating the activation of specific defence pathways with the relative stress resistance of the investigated species. Also, species of the genus could be economically attractive as ‘new’ crops for ‘saline’ and ‘arid’, sustainable agriculture, as medicinal plants, highly nutritious vegetable crops and ornamentals.

Effect of soil salinity on fructan content and polymerization degree in the sprouting tubers of Jerusalem artichoke (Helianthus tuberosus L.)

In addition to their role as reserve carbohydrates, fructans have been recognized as compounds that are protective against adverse environments. The aim of this study was to identify changes in the content and the degree of polymerization (DP) of fructan in sprouting tubers of Jerusalem artichoke under salt stress. Fructan was extracted from tubers at 1, 3, 5, and 7 days after planting in sandy loam soil irrigated with NaCl solution. Fructan accumulation and polymerization and the expression of genes encoding enzymes for fructan synthesis and degradation were evaluated. No significant differences between the control and treatment groups were observed until 5 days after sowing. The highest level of salinity (250 mM) not only inhibited sprouting and root growth but also decreased the level of fructan in the tubers. The proportion of fructan at DP 2-5 rapidly increased one day after sowing and then decreased over time. Under various NaCl treatments, at 7 days after sowing, all fructans except fructan at DP 6-10 were present in proportions less than or equal to the control. The variation in the DP of fructan was related to the transcription level of fructan metabolism genes. Fructan may support sprouting or resistance to salt stress by changing the DP of fructan molecules through hydrolysis without changing the total amount of fructan. The low-molecular-weight oligosaccharides (DP < 5) may be the major carbohydrates that support tuber sprouting or that are involved in protection from salt stress.