Nitric Oxide Induces Flowering in the Duckweed Lemna aequinoctialis Welw. (Syn. L. paucicostata Hegelm.) Under Noninductive Conditions

Nitric oxide (NO) plays diverse roles in the growth and development of plants and in their responses to various abiotic and biotic stresses. It has also been reported to repress flowering in Arabidopsis thaliana. In the present study, NO donors sodium nitroprusside (SNP), S-nitroso-N-acetyl penicillamine (SNAP), and 3-morpholinosydnonimine (SIN-1) induced flowering in Lemna aequinoctialis 6746 (a short-day strain) and in L. aequinoctialis LP₆ (a photoperiod-insensitive strain) under noninductive conditions. Nitrate and nitrite, two stable metabolites of NO, did not induce flowering. On the other hand, cyanide donors potassium ferricyanide {K₃[Fe(CN)₆]} and potassium cyanide (KCN) induced flowering in both strains under noninductive conditions. The flowering induced under a 8-h daily photoperiod regime in the short-day strain L. aequinoctialis 6746 was inhibited by NO and cyanide donors. Vegetative multiplication of both strains was adversely affected by NO and cyanide donors, irrespective of the photoperiod conditions. The observed effects of NO donors on flowering were substantially negated by NO scavengers c-PTIO [2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide] and methylene blue. This confirmed the role of NO in induction of flowering. The inductive effect of CN⁻ also appeared to be partly mediated through NO as NO scavengers partially negated the effect of CN⁻.     

NAD+ supplementation prevents STING‐induced senescence in ataxia telangiectasia by improving mitophagy

Senescence phenotypes and mitochondrial dysfunction are implicated in aging and in premature aging diseases, including ataxia telangiectasia (A‐T). Loss of mitochondrial function can drive age‐related decline in the brain, but little is known about whether improving mitochondrial homeostasis alleviates senescence phenotypes. We demonstrate here that mitochondrial dysfunction and cellular senescence with a senescence‐associated secretory phenotype (SASP) occur in A‐T patient fibroblasts, and in ATM‐deficient cells and mice. Senescence is mediated by stimulator of interferon genes (STING) and involves ectopic cytoplasmic DNA. We further show that boosting intracellular NAD⁺ levels with nicotinamide riboside (NR) prevents senescence and SASP by promoting mitophagy in a PINK1‐dependent manner. NR treatment also prevents neurodegeneration, suppresses senescence and neuroinflammation, and improves motor function in Atm^−/− mice. Our findings suggest a central role for mitochondrial dysfunction‐induced senescence in A‐T pathogenesis, and that enhancing mitophagy as a potential therapeutic intervention.     

Putative role of ethylene in Datura metel microspore embryogenesis

The role of ethylene in microspore embryogenesis was analyzed by studying the effect of cobalt ions, silver ions, methionine and Ethrel on the androgenic response of in vitro cultured anthers of Datura metel L. Cobalt and silver ions, provided in the form of cobalt chloride and silver nitrate, respectively, decreased the average number of embryos/plantlets developed per anther, at all the concentrations tested. In contrast, methionine (10⁻⁵–10⁻³ M ) and Ethrel (10⁻⁶ and 10⁻⁵ M ) stimulated embryo formation. The optimal enhancement was recorded at 10⁻⁵ M of both methionine and Ethrel.     

Changes in sialic acid and fucose contents of enterocytes across the crypt-villus axis in developing rat intestine

Alterations in sialic acid and fucose contents of different populations of epithelial cells have been studied in suckling and adult rat intestine. The progression of cells from crypt base to villus tip is associated with an increase in sialic acid and a decrease in fucose levels of the cells in adult rats. In suckling pups, sialic acid is uniformly distributed along the length of villi, and fucose is richly (P less than 0.01) present in cryptic cells compared to that at the villus tip. Adult-type changes in sialylation and fucosylation of enterocytes across the crypt-villus axis were precociously produced by cortisone administration to suckling pups. Thyroxine treatment was less effective in influencing the glycosylation process in rat intestine.     

Nitric oxide is involved in salicylic acid-induced flowering of Lemna aequinoctialis Welw.

Salicylic acid (SA) is a well-known inducer of flowering in Lemna under both non-inductive and inductive photoperiod conditions. However, the underlying mechanism is not well understood. Herein, we report for the first time that nitric oxide (NO) is partially involved in SA-induced flowering in L. aequinoctialis (Syn. L. paucicostata Hegelm.). Our results demonstrated that SA-induced flowering is significantly reduced by exogenous application of NO scavengers; 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide and methylene blue, nitric oxide synthase inhibitors; N-ω-nitro-l-arginine and N-ω-nitro-l-arginine-methyl ester hydrochloride, and nitrate reductase inhibitor; sodium tungstate in two strains of Lemna viz. 6746 and LP₆. Altogether our present findings shed a light on the new role of NO in SA-induced flowering and open interesting directions that need further investigation.     

DNA barcoding of endangered Indian Paphiopedilum species

The indiscriminate collections of Paphiopedilum species from the wild for their exotic ornamental flowers have rendered these plants endangered. Although the trade of these endangered species from the wild is strictly forbidden, it continues unabated in one or other forms that elude the current identification methods. DNA barcoding that offers identification of a species even if only a small fragment of the organism at any stage of development is available could be of great utility in scrutinizing the illegal trade of both endangered plant and animal species. Therefore, this study was undertaken to develop DNA barcodes of Indian species of Paphiopedilum along with their three natural hybrids using loci from both the chloroplast and nuclear genomes. The five loci tested for their potential as effective barcodes were RNA polymerase-β subunit (rpoB), RNA polymerase-β' subunit (rpoC1), Rubisco large subunit (rbcL) and maturase K (matK) from the chloroplast genome and nuclear ribosomal internal transcribed spacer (nrITS) from the nuclear genome. The intra- and inter-specific divergence values and species discrimination rates were calculated by Kimura 2 parameter (K2P) method using mega 4.0. The matK with 0.9% average inter-specific divergence value yielded 100% species resolution, thus could distinguish all the eight species of Paphiopedilum unequivocally. The species identification capability of these sequences was further confirmed as each of the matK sequences was found to be unique for the species when a blast analysis of these sequences was carried out on NCBI. nrITS, although had 4.4% average inter-specific divergence value, afforded only 50% species resolution. DNA barcodes of the three hybrids also reflected their parentage.     

COPI–TRAPPII activates Rab18 and regulates its lipid droplet association

The transport protein particle (TRAPP) was initially identified as a vesicle tethering factor in yeast and as a guanine nucleotide exchange factor (GEF) for Ypt1/Rab1. In mammals, structures and functions of various TRAPP complexes are beginning to be understood. We found that mammalian TRAPPII was a GEF for both Rab18 and Rab1. Inactivation of TRAPPII‐specific subunits by various methods including siRNA depletion and CRISPR–Cas9‐mediated deletion reduced lipolysis and resulted in aberrantly large lipid droplets. Recruitment of Rab18 onto lipid droplet (LD) surface was defective in TRAPPII‐deleted cells, but the localization of Rab1 on Golgi was not affected. COPI regulates LD homeostasis. We found that the previously documented interaction between TRAPPII and COPI was also required for the recruitment of Rab18 to the LD. We hypothesize that the interaction between COPI and TRAPPII helps bring TRAPPII onto LD surface, and TRAPPII, in turn, activates Rab18 and recruits it on the LD surface to facilitate its functions in LD homeostasis.     

Gum katira – a cheap gelling agent for plant tissue culture media

Gum katira, an insoluble gum derived from the bark of Cochlospermum religiosum, has been successfully used as a gelling agent in tissue culture media for in vitro shoot formation and rooting in Syzygium cuminii and somatic embryogenesis in Albizzia lebbeck. The epicotyl segments, excised from in vitro grown seedlings of S. cuminii, developed shoots when cultured on MS medium (Murashige and Skoog, 1962), supplemented with 4% sucrose and 1 mg l^–1 BA. The so-developed shoots were rooted on Knop's medium, augmented with 2% sucrose and 1 mg l^–1 IAA. For somatic embryogenesis, hypocotyl segments derived from in vitro developed seedlings of A. lebbeck were cultured on B5 medium containing 2% sucrose. Media were gelled with either 3% gum or 0.9% agar. The quantitative response obtained on media fortified with either of the gelling agents was not significantly different. The media gelled with gum katira were almost as transparent as the liquid medium. However, viscosity of gum katira gelled medium was less than one-sixth of the viscosity of agar-gelled media, and therefore, shaking ofthe culture vessel often resulted in submersion of the explants. Nevertheless, even these submerged explants responded positively. To increase the firmness of the gum katira-gelled medium, various combinations of agar (0.2–0.6%) and gum (1–3%) were used. However, the viscosities of the media gelled with 3% gum katira as well as different concentrations of agar (0.2–0.6%) were lower than that of the medium containing only gum katira (3%). Moreover, the explant productivity obtained in neither of these combinations was more than those recorded on the control media, which were gelled either with 0.9% agar or 3% gum alone.     

Pectic oligosaccharides from agricultural by-products: production,characterization and health benefits

Pectin containing agricultural by-products are potential sources of a new class of prebiotics known as pectic oligosaccharides (POS). In general, pectin is made up of homogalacturonan (HG, α-1,4-linked galacturonic acid monomers) and rhamnogalacturonan (RG, alternate galacturonic acid and rhamnose backbone with neutral side chains). Controlled hydrolysis of pectin containing agricultural by-products like sugar beet, apple, olive and citrus by chemical, enzymatic and hydrothermal can be used to produce oligo-galacturonides (GalpOS), galacto-oligosaccharides (GalOS), rhamnogalacturonan-oligosaccharides (RGOS), etc. However, extensive research is needed to establish the role of POS, both as a prebiotic as well as therapeutic agent. This review comprehensively covers different facets of POS, including the nature and chemistry of pectin and POS, potential agricultural residual sources of pectin, pre-treatment methods for facilitating selective extraction of pectin, identification and characterization of POS, health benefits and important applications of POS in food and feed. This review has been compiled to establish a platform for future research in the purification and characterization of POS and for in vivo and in vitro studies of important POS, so that they could be commercially exploited.