Red Mexican grapefruit: a novel source for bioactive limonoids and their antioxidant activity

Citrus limonoids have shown to inhibit the growth of cancer in colon, lung, mouth, stomach and breast in animal and cell culture studies. For the first time in the present study, an attempt has been made to isolate antioxidant fractions and five limonoids from red Mexican grapefruit seeds. Defatted seed powder was successively extracted with hexane, ethyl acetate (EtOAc), acetone, methanol (MeOH) and MeOH/water and the extracts were concentrated under vacuum. Radical scavenging activity of 1,1-diphenyl-2-picrylhydrazyl (DPPH) and total phenolic content were also measured for comparison with the antioxidant capacity in the phosphomolybdenum method for the above extracts. Acetone and MeOH extracts, respectively, showed the highest (85.7%) and lowest (53.3%) radical scavenging activity, at 500 ppm. The total phenolic contents were found to be highest in the acetone extract (15.94%) followed by the MeOH extract (5.92%), ethyl acetate extract (5.54%) and water extract (5.26%). Antioxidant capacity of the extracts as equivalents to ascorbic acid (micromol/g of the extract) was in the order, EtOAc extract > acetone extract > water extract > methanol extract. Furthermore, the EtOAC and acetone extracts were loaded onto silica gel columns to obtain four limonoid aglycons. MeOH fraction was loaded onto a dowex-50 and sepabeads resin column to obtain a limonoid glucoside. The purity of the isolated five compounds was analyzed by HPLC using a C18 column and UV detection at 210 nm. Finally, the structures of the compounds were identified as obacunone, nomilin, limonin, deacetylnomilin (DAN) and limonin-17-beta-D-glucopyranoside (LG) using 1H and 13C NMR studies.     

Characterization of the wave phenomenon of flash-induced chlorophyll fluorescence in Chlamydomonas reinhardtii

Flash-induced chlorophyll fluorescence relaxation is a powerful tool to monitor the reoxidation reactions of the reduced primary quinone acceptor, Q_A^? by Q_B and the plastoquinone (PQ) pool, as well as the charge recombination reactions between the donor and acceptor side components of Photosystem II (PSII). Under certain conditions, when the PQ pool is highly reduced (e.g. in microaerobic conditions), a wave phenomenon appears in the fluorescence relaxation kinetics, which reflects the transient reoxidation and re-reduction of Q_A^? by various electron transfer processes, which in cyanobacteria is mediated by NAD(P)H dehydrogenase (NDH-1). The wave phenomenon was also observed and assigned to the operation of type 2 NAD(P)H dehydrogenase (NDH-2) in the green alga Chlamydomonas reinhardtii under hydrogen-producing conditions, which required a long incubation of algae under sulphur deprivation (Krishna et al. J Exp Bot 70 (21):6321–6336, 2019). However, the conditions that induce the wave remained largely uncharacterized so far in microalgae. In this work, we investigated the wave phenomenon in Chlamydomonas reinhardtii under conditions that lead to a decrease of PSII activity by applying hydroxylamine treatment, which impacts the donor side of PSII in combination with a strongly reducing environment of the PQ pool (microaerobic conditions). A similar wave phenomenon could be induced by photoinhibitory conditions (illumination with strong light in the presence of the protein synthesis inhibitor lincomycin). These results indicate that the fluorescence wave phenomenon is activated in green algae when the PSII activity decreases relative to Photosystem I (PS I) activity and the PQ pool is strongly reduced. Therefore, the fluorescence wave could be used as a sensitive indicator of altered intersystem electron transfer processes, e.g. under stress conditions.

     

Correction to: Exogenous dsRNA-mediated field protection against Pigeonpea sterility mosaic emaravirus

Journal of Plant Biochemistry and Biotechnology - Unfortunately, the title of the article was incorrectly published in the original publication. The correct title is updated.     

Phosphoproteomic screening identifies Rab GTPases as novel downstream targets of PINK1

Mutations in the PTEN‐induced kinase 1 (PINK1) are causative of autosomal recessive Parkinson''s disease (PD). We have previously reported that PINK1 is activated by mitochondrial depolarisation and phosphorylates serine 65 (Ser⁶⁵) of the ubiquitin ligase Parkin and ubiquitin to stimulate Parkin E3 ligase activity. Here, we have employed quantitative phosphoproteomics to search for novel PINK1‐dependent phosphorylation targets in HEK (human embryonic kidney) 293 cells stimulated by mitochondrial depolarisation. This led to the identification of 14,213 phosphosites from 4,499 gene products. Whilst most phosphosites were unaffected, we strikingly observed three members of a sub‐family of Rab GTPases namely Rab8A, 8B and 13 that are all phosphorylated at the highly conserved residue of serine 111 (Ser¹¹¹) in response to PINK1 activation. Using phospho‐specific antibodies raised against Ser¹¹¹ of each of the Rabs, we demonstrate that Rab Ser¹¹¹ phosphorylation occurs specifically in response to PINK1 activation and is abolished in HeLa PINK1 knockout cells and mutant PINK1 PD patient‐derived fibroblasts stimulated by mitochondrial depolarisation. We provide evidence that Rab8A GTPase Ser¹¹¹ phosphorylation is not directly regulated by PINK1 in vitro and demonstrate in cells the time course of Ser¹¹¹ phosphorylation of Rab8A, 8B and 13 is markedly delayed compared to phosphorylation of Parkin at Ser⁶⁵. We further show mechanistically that phosphorylation at Ser¹¹¹ significantly impairs Rab8A activation by its cognate guanine nucleotide exchange factor (GEF), Rabin8 (by using the Ser111Glu phosphorylation mimic). These findings provide the first evidence that PINK1 is able to regulate the phosphorylation of Rab GTPases and indicate that monitoring phosphorylation of Rab8A/8B/13 at Ser¹¹¹ may represent novel biomarkers of PINK1 activity in vivo. Our findings also suggest that disruption of Rab GTPase‐mediated signalling may represent a major mechanism in the neurodegenerative cascade of Parkinson''s disease.     

Taxonomic importance of seed macro‐ and micro‐morphology in Abelmoschus (Malvaceae)

Seed morphology of Abelmoschus is known to be variable, but patterns of variation have never been critically studied. We studied seed macro‐ and micro‐morphological characters, including seed shape/size, seed coat pattern and trichome density/structure in multiple samples to evaluate the taxonomic significance of seed characters. Among the studied characters, seed shape and trichome structure were found to have major taxonomic importance and proved to be valuable characters for separating taxa. Two main seed types were present: seeds with deciduous trichomes and seeds with persistent trichomes. These characters offer significant evidence to the distinctness of certain species (A. esculentus, A. moschatus subsp. moschatus, A. moschatus subsp. tuberosus, A. crinitus and A. angulosus). Further, our results indicate that A. moschatus subsp. tuberosus should be maintained as a separate subspecies while A. manihot subsp. tetraphyllus var. pungens may be merged in A. angulosus. No significant intraspecific variation was observed, except in A. esculentus. We conclude that seed coat sculpturing and seed trichomes do indeed provide stable and diagnostic characters for many morphologically closely related taxa of Abelmoschus and that LM/SEM techniques can be useful in solving systematic problems and management of Abelmoschus genetic resources.     

Genetic variants in root architecture-related genes in a Glycine soja accession,a potential resource to improve cultivated soybean

Background

Root system architecture is important for water acquisition and nutrient acquisition for all crops. In soybean breeding programs, wild soybean alleles have been used successfully to enhance yield and seed composition traits, but have never been investigated to improve root system architecture. Therefore, in this study, high-density single-feature polymorphic markers and simple sequence repeats were used to map quantitative trait loci (QTLs) governing root system architecture in an inter-specific soybean mapping population developed from a cross between Glycine max and Glycine soja.

Results

Wild and cultivated soybean both contributed alleles towards significant additive large effect QTLs on chromosome 6 and 7 for a longer total root length and root distribution, respectively. Epistatic effect QTLs were also identified for taproot length, average diameter, and root distribution. These root traits will influence the water and nutrient uptake in soybean. Two cell division-related genes (D type cyclin and auxin efflux carrier protein) with insertion/deletion variations might contribute to the shorter root phenotypes observed in G. soja compared with cultivated soybean. Based on the location of the QTLs and sequence information from a second G. soja accession, three genes (slow anion channel associated 1 like, Auxin responsive NEDD8-activating complex and peroxidase), each with a non-synonymous single nucleotide polymorphism mutation were identified, which may also contribute to changes in root architecture in the cultivated soybean. In addition, Apoptosis inhibitor 5-like on chromosome 7 and slow anion channel associated 1-like on chromosome 15 had epistatic interactions for taproot length QTLs in soybean.

Conclusion

Rare alleles from a G. soja accession are expected to enhance our understanding of the genetic components involved in root architecture traits, and could be combined to improve root system and drought adaptation in soybean.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1334-6) contains supplementary material, which is available to authorized users.     

Validated TLC method for simultaneous quantitation of kutkoside and picroside‐I from Kutki extract

Introduction – The two iridoid glycosides kutkoside and picroside‐I are the active hepatoprotective principles of Picrorhiza kurroa Royle ex Benth (Scrophulariaceae), commonly known as Kutki. Quantitation of these phytoconstituents is important for the routine quality control of Kutki extract. Objective – To develop and validate a simple, precise and rapid thin‐layer chromatography (TLC) method for the simultaneous quantitation of kutkoside and picroside‐I in Kutki extract. Methodology – The analysis was performed on a TLC precoated silica gel 60 F₂₅₄ plate with ethyl acetate:methanol:glacial acetic acid:formic acid (25:5:1:1, v/v/v/v) as mobile phase. Densitometric evaluation of kutkoside and picroside‐I was carried out at 265 nm and the mobile phase showed good resolution with R_f values 0.42 ± 0.03 and 0.61 ± 0.03 for kutkoside and picroside‐I, respectively. The method was validated in terms of specificity, linearity, accuracy and precision. Results – The content of kutkoside and picroside‐I was found to be 2.18 and 1.90%, respectively, and was comparable with those obtained by HPLC. The linearity was found to be in the range of 80–480 ng/spot for both kutkoside and picroside‐I. The average recovery values were found to be 96.5 and 96.0% for kutkoside and picroside‐I, respectively. Conclusion – The developed method was found to be relatively simple, precise and reproducible for the simultaneous quantitation of kutkoside and picroside‐I. The method does not employ any derivatisation procedure and can be used as a quality control tool for the routine analysis of commercial Kutki extracts. Copyright © 2010 John Wiley & Sons, Ltd.     

Bayesian geostatistics in health cartography: the perspective of malaria

Maps of parasite prevalences and other aspects of infectious diseases that vary in space are widely used in parasitology. However, spatial parasitological datasets rarely, if ever, have sufficient coverage to allow exact determination of such maps. Bayesian geostatistics (BG) is a method for finding a large sample of maps that can explain a dataset, in which maps that do a better job of explaining the data are more likely to be represented. This sample represents the knowledge that the analyst has gained from the data about the unknown true map. BG provides a conceptually simple way to convert these samples to predictions of features of the unknown map, for example regional averages. These predictions account for each map in the sample, yielding an appropriate level of predictive precision.