Cell wall integrity, genotoxic injury and PCD dynamics in alfalfa saponin-treated white poplar cells highlight a complex link between molecule structure and activity

Triterpenic saponins from Medicago marina L

The saponin composition of leaves and roots from Medicago marina L., sea medic, was investigated by a combination of chromatographic, spectroscopic and spectrometric (GC, LC, ESI-MS/MS, NMR) methods. Several compounds were detected and quantified by HPLC using the external standard method. Saponins from this plant species consist of a mixture of high molecular weight bidesmosidic derivatives of medicagenic and zanhic acid, containing up to six sugars in the molecules. Six of the detected saponins were previously isolated and reported as constituents of other Medicago spp.; one saponin was previously described in other plant species; four saponins are undescribed compounds in Medicago and never reported before in other plant species. These are: 3-O-β-D-glucopyranosyl-(1 → 2)-β-D-glucopyranosylzanhic acid 28-O-β-D-xylopyranosyl-(1 → 4)-[β-D-apiofuranosyl-(1 → 3)]-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosyl ester; 3-O-β-D-glucopyranosyl-(1 → 2)-β-D-glucopyranosylzanhic acid 28-O-β-D-xylopyranosyl-(1 → 4)-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosyl ester; 3-O-β-D-glucopyranosyl-(1 → 2)-β-D-glucopyranosylmedicagenic acid 28-O-β-D-xylopyranosyl-(1 → 4)-[α-L-arabinopyranosyl-(1 → 3)]-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosyl ester and 3-O-β-D-glucopyranosylmedicagenic acid 28-O-β-D-xylopyranosyl-(1 → 4)-[α-L-arabinopyranosyl-(1 → 3)]-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosyl ester. The specific saponins synthesized by M. marina may have a role in its tolerance to environment, representing a reservoir of osmolytic sugars.

Expression profiling of immature florets of IR58025A, a wild-abortive cytoplasmic male sterile line of rice and its cognate, isonuclear maintainer line, IR58025B

Interaction between gene products encoded by the cytoplasm and nucleus form the core of wild abortive cytoplasmic male sterile (WA-CMS) system of hybrid breeding in rice. Gaining insights into such interactions can be helpful in the development of better three-line rice hybrids and also identify novel male sterility systems. In the present study, the whole transcriptome profiles of immature florets of IR58025A, a WA-CMS line and its isonuclear maintainer line, IR58025B, collected at pre-anthesis stage were compared to delineate the pathways involved in pollen abortion and male sterility. Among the 774 differentially expressed transcripts (DETs), 496 were down regulated and 278 were up regulated in IR58025A compared to IR58025B. The genes associated with oxidative stress response, defense response, etc. were significantly up-regulated, while those associated with respiration, cell wall modifications, pectinesterase activity, etc. were significantly down-regulated in the WA-CMS line. Gene ontology and pathway enrichment analyses revealed the down-regulation of both nuclear and organellar genes involved in key metabolic processes of cell respiration, photosynthesis and other energy yielding metabolites in IR58025A, relative to IR58025B, indicating a general shift toward conservation of energy and other key resources in the florets of WA-CMS line. The data derived from RNA-Seq analysis were validated through qRT-PCR analysis. Based on the results obtained, it can be hypothesized that pollen abortion principally occurs due to up-regulation of pathways leading to oxidative stress leading to energy starvation conditions in consonance with reduced expression of genes associated with the cell wall formation, respiration, and other key metabolic processes.

In Vitro Anthelmintic Activity of Saponins Derived from Medicago spp. Plants against Donkey Gastrointestinal Nematodes

With the aim to find new effective natural compounds for the control of nematodes, the in vitro anthelminthic properties of purified 1% saponins showing different chemical compositions and derived from Medicago sativa (MS), Medicago arborea (MA), Medicago polymorpha cultivar ‘Santiago’ (MPS), M. polymorpha cultivar ‘Anglona’ (MPA), and 1% prosapogenins from M. sativa (MSp), were evaluated and compared. As a source of nematode eggs, pooled fresh fecal samples taken from dairy donkeys naturally infected by gastrointestinal nematodes were used. From fecal samples, eggs were recovered, suspended in deionized water, and used immediately in the bioassay (egg hatch test). The activity of the tested compounds was compared to positive (0.1% thiabendazole) and negative (deionized water and 1% DMSO) controls. All experiments were repeated in triplicate and the obtained data were statistically analyzed. All the tested plant compounds caused a significant (p < 0.05) inhibition of nematode egg hatching (>80%). Moreover, all saponins and prosapogenins showed in vitro anthelmintic properties statistically comparable to that of the reference drug (p < 0.05), except for MPS extract. Obtained results showed that the different Medicago saponins evaluated in this study possess high anthelmintic properties against gastrointestinal nematodes of dairy donkeys, although to a different extent depending on their composition.

DNA Diffusion Assay Applied to Plant Cells

DNA diffusion assay is a simple, sensitive and reliable technique which allows the assessment of programmed cell death (PCD) or necrosis events based on nuclear morphology. It consists in isolating nuclei from plant material, which are then embedded in agarose and subjected to lysis in alkaline buffers. Under these conditions, and due to the presence of abundant alkali-labile sites in the DNA, small pieces of DNA diffuse in the agarose gel giving a specific halo appearance when stained with fluorescent dyes like DAPI (4',6-diamidino-2-phenylindole). Here, we describe an optimized protocol for DNA diffusion assay applied to different types of plant cells/tissues, indicating all the critical steps required for a successful experimental procedure.

The use of comet assay in plant toxicology: recent advances

The systematic study of genotoxicity in plants induced by contaminants and other stress agents has been hindered to date by the lack of reliable and robust biomarkers. The comet assay is a versatile and sensitive method for the evaluation of DNA damages and DNA repair capacity at single-cell level. Due to its simplicity and sensitivity, and the small number of cells required to obtain robust results, the use of plant comet assay has drastically increased in the last decade. For years its use was restricted to a few model species, e.g., Allium cepa, Nicotiana tabacum, Vicia faba, or Arabidopsis thaliana but this number largely increased in the last years. Plant comet assay has been used to study the genotoxic impact of radiation, chemicals including pesticides, phytocompounds, heavy metals, nanoparticles or contaminated complex matrices. Here we will review the most recent data on the use of this technique as a standard approach for studying the genotoxic effects of different stress conditions on plants. Also, we will discuss the integration of information provided by the comet assay with other DNA-damage indicators, and with cellular responses including oxidative stress, cell division or cell death. Finally, we will focus on putative relations between transcripts related with DNA damage pathways, DNA replication and repair, oxidative stress and cell cycle progression that have been identified in plant cells with comet assays demonstrating DNA damage.