Nitric oxide mediates strigolactone signaling in auxin and ethylene-sensitive lateral root formation in sunflower seedlings

Strigolactones (SLs) play significant role in shaping root architecture whereby auxin-SL crosstalk has been observed in SL-mediated responses of primary root elongation, lateral root formation and adventitious root (AR) initiation. Whereas GR24 (a synthetic strigolactone) inhibits LR and AR formation, the effect of SL biosynthesis inhibitor (fluridone) is just the opposite (root proliferation). Naphthylphthalamic acid (NPA) leads to LR proliferation but completely inhibits AR development. The diffusive distribution of PIN1 in the provascular cells in the differentiating zone of the roots in response to GR24, fluridone or NPA treatments further indicates the involvement of localized auxin accumulation in LR development responses. Inhibition of LR formation by GR24 treatment coincides with inhibition of ACC synthase activity. Profuse LR development by fluridone and NPA treatments correlates with enhanced [Ca²⁺]_cyt in the apical region and differentiating zones of LR, indicating a critical role of [Ca²⁺] in LR development in response to the coordinated action of auxins, ethylene and SLs. Significant enhancement of carotenoid cleavage dioxygenase (CCD) activity (enzyme responsible for SL biosynthesis) in tissue homogenates in presence of cPTIO (NO scavenger) indicates the role of endogenous NO as a negative modulator of CCD activity. Differences in the spatial distribution of NO in the primary and lateral roots further highlight the involvement of NO in SL-modulated root morphogenesis in sunflower seedlings. Present work provides new report on the negative modulation of SL biosynthesis through modulation of CCD activity by endogenous nitric oxide during SL-modulated LR development.     

CYSL-1 interacts with the O2-sensing hydroxylase EGL-9 to promote H2S-modulated hypoxia-induced behavioral plasticity in C. elegans

The C. elegans HIF-1 proline hydroxylase EGL-9 functions as an O(2) sensor in an evolutionarily conserved pathway for adaptation to hypoxia. H(2)S accumulates during hypoxia and promotes HIF-1 activity, but how H(2)S signals are perceived and transmitted to modulate HIF-1 and animal behavior is unknown. We report that the experience of hypoxia modifies a C. elegans locomotive behavioral response to O(2) through the EGL-9 pathway. From genetic screens to identify novel regulators of EGL-9-mediated behavioral plasticity, we isolated mutations of the gene cysl-1, which encodes a C. elegans homolog of sulfhydrylases/cysteine synthases. Hypoxia-dependent behavioral modulation and H(2)S-induced HIF-1 activation require the direct physical interaction of CYSL-1 with the EGL-9 C terminus. Sequestration of EGL-9 by CYSL-1 and inhibition of EGL-9-mediated hydroxylation by hypoxia together promote neuronal HIF-1 activation to modulate behavior. These findings demonstrate that CYSL-1 acts to transduce signals from H(2)S to EGL-9 to regulate O(2)-dependent behavioral plasticity in C. elegans.     

Ion distribution measured by electron probe X-ray microanalysis in apoplastic and symplastic pathways in root cells in sunflower plants grown in saline medium

Little is known about how salinity affects ions distribution in root apoplast and symplast. Using x-ray microanalysis, ions distribution and the relative contribution of apoplastic and symplastic pathways for delivery of ions to root xylem were studied in sunflower plants exposed to moderate salinity (EC=6). Cortical cells provided a considerably extended Na+ and Cl- storage facility. Their contents are greater in cytoplasm (root symplast) as compared to those in intercellular spaces (root apoplast). Hence, in this level of salinity, salt damage in sunflower is not dehydration due to extracellular accumulation of sodium and chloride ions, as suggested in the Oertli hypothesis. On the other hand, reduction in calcium content due to salinity in intercellular space is less than reduction in the cytoplasm of cortical cells. It seems that sodium inhibits the radial movement of calcium in symplastic pathway more than in the apoplastic pathway. The cell wall seems to have an important role in providing calcium for the apoplastic pathway. Redistribution of calcium from the cell wall to intercellular space is because of its tendency towards xylem through the apoplastic pathway. This might be a strategy to enhance loading of calcium to xylem elements and to reduce calcium deficiency in young leaves under salinity. This phenomenon may be able to increase salt tolerance in sunflower plants. Supplemental calcium has been found to be effective in reducing radial transport of Na+ across the root cells and their loading into the xylem, but not sodium absorption. Supplemental calcium enhanced Ca2+ uptake and influx into roots and transport to stele.     

Neonatal amygdalae and hippocampi are influenced by genotype and prenatal environment,and reflected in the neonatal DNA methylome

The amygdala and hippocampus undergo rapid development in early life. The relative contribution of genetic and environmental factors to the establishment of their developmental trajectories has yet to be examined. We performed imaging on neonates and examined how the observed variation in volume and microstructure of the amygdala and hippocampus varied by genotype, and compared with prenatal maternal mental health and socioeconomic status. Gene × Environment models outcompeted models containing genotype or environment only to best explain the majority of measures but some, especially of the amygdaloid microstructure, were best explained by genotype only. Models including DNA methylation measured in the neonate umbilical cords outcompeted the Gene and Gene × Environment models for the majority of amygdaloid measures and minority of hippocampal measures. This study identified brain region‐specific gene networks associated with individual differences in fetal brain development. In particular, genetic and epigenetic variation within CUX1 was highlighted.     

Regulation of gametangial formation in bryophytes

Under in vitro conditions gametangial formation in bryophytes can be regulated by a variety of physical and chemical factors. Liverworts are relatively more sensitive to photoperiod than are mosses. With the exception ofRiccia crystallina all species of liverworts thus far investigated are either long-day or short-day plants. Among mosses, all butSphagnum plumulosum appear to be independent of photoperiod for the onset of the reproductive phase. The photoperiodic response in liverworts increases with increasing light intensity. Mosses, on the other hand, exhibit differential behavior.Leptobryum pyriforme andBartramidula bartramioides exhibit a linear relationship with light intensity for this response, whereasBryum argenteum, B. coronatum andBarbula gregaria have a specific light intensity requirement for optimal response. The photoperiodic effect in bryophytes is operative within certain temperature limits. Most bryophytes do not require a low temperature pretreatment for gametangial induction. Some become fertile in a broad temperature range, whereas others require a specific temperature. Among chemical factors, carbohydrates in general enhance gametangial formation.Riccia crystallina andBartramidula bartramioides develop gametangia in the presence of a carbohydrate, butBryum spp. (B. argenteum andB. coronatum) andBarbula gregaria respond even in its absence. High carbohydrate-nitrogen ratio seems more favorable for the onset of reproductive phase. Bryophytes respond differentially to various forms of nitrogen. Depletion of inorganic nitrogen (nitrate or ammonium) significantly favors gametangial induction. On the other hand, organic nitrogen (such as amino acids, peptone and urea) has differential effects on the enhancement of antheridial and archegonial formation in liverworts. Growth hormones have variable effects on gametangial induction. Indole-3-acetic acid increases archegonial formation inRiccia crystallina, but it is more favorable for antheridial production in mosses likeBryum coronatum, B. argenteum andBarbula gregaria. Gibberellins enhance antheridial formation in all the investigated bryophytes. Cytokinins stimulate induction of archegonia and inhibit antheridial formation inRiccia crystallina andBryum argenteum. Auxins, gibberellins and cytokinins also interact in eliciting the response. Iron and copper chelating agents such as EDTA and EDDHA favor vegetative growth and gametangial formation. InRiccia these chelates enhance archegonial production more than antheridial formation, but inBryum argenteum their effect is just the reverse. Salicylic acid, known to chelate iron and copper in certain animal systems, inhibits gametangial formation in most bryophytes, except inBartramidula in which it enhances vegetative growth as well as gametangial formation. InBryum argenteum the effect of these chelates is accompanied with marked changes in the endogenous levels of iron and copper. Iron appears to favor the onset of reproductive phase, whereas copper is inhibitory. Cyclic AMP, a well known mediator of hormone action in animal systems, enhances gametangial formation inBryum argenteum. The response is specific and is mimicked by phosphodiesterase inhibitors. Cyclic AMP also increases antheridial production inBryum coronatum andBarbula gregaria. InBryum argenteum it overcomes the inhibitory effect of ammonium ions and high concentrations of sucrose on gametangial formation. In addition to the above factors, pH and nutritional status of the medium also affect the onset of reproductive phase. Bryophytes exhibit maximum response in a definite pH range. Moreover, a specific change in pH of the medium is observed during gametangial initiation. Nutritional status, as affected by the concentration of nutrients in the medium, has varied effects on gametangial formation. In most instances dilution of the medium is more favorable for the response. Certain other factors, such as yeast extract and animal sex hormones, also enhance the formation of antheridia and archegonia. The onset of the reproductive phase involves metabolic changes in the differentiating tissues. Archegonial initiation is accomplished by intense metabolic activities, and in certain liverworts there is an increase in the content of carbohydrates, auxins, RNA and proteins, whereas the level of total nitrogen drops. Besides this a number of enzymes and phenolic compounds also exhibit marked qualitative and quantitative changes. Once gametangia are induced under in vitro conditions, fertilization can be accomplished by flooding the cultures bearing mature gametangia with sterile, distilled water. Development of sporophytes is markedly affected by temperature and nutritional status of the medium.     

Ca uptake and plasma membrane depolarization associated with blue light-sensitive exogenous NADH oxidation by Cuscuta protoplasts

Protoplasts isolated from the apical segments of Cuscuta reflexa exhibited blue light-sensitive PM-linked NADH oxidase activity and increased rate of Ca²⁺-uptake in presence of NADH in dark, which was also stimulated by blue light. Contrary to marginal inhibition by Con A treatment, the ATPase inhibitors significantly inhibited the Ca²⁺ uptake by the protoplasts both in dark and under blue light. The Ca²⁺-calmodulin antagonists, W-7 and calmidazolium, also inhibited Ca²⁺-uptake by protoplasts under similar conditions. The state of PM polarization was monitored by the fluorescent dye 9-amino acridine. It was observed that PM-linked NADH oxidation caused hyperpolarization of the membrane, the exposure of which to blue light resulted in membrane depolarization. The presence of Ca²⁺-calmodulin antagonists or Con A treatment completely abolished the blue light-induced membrane depolarization. It is argued that these actities at the PM, having some glycoproteic components, are functionally closely involved in blue light-induced signal transduction in Cuscuta     

DNA and LNA oligonucleotides containing N2'-functionalised derivatives of 2'-amino-2'-deoxyuridine

Synthesis of various N-acylated derivatives of 2'-amino-2'-deoxyuridine is described together with their incorporation into DNA and LNA oligonucleotides using the phosphoramidite approach on an automated DNA synthesizer. The thermal stabilities of duplexes formed by these 2'-amino-DNA-modified DNA or LNA/DNA chimeric strands and complementary DNA or RNA strands have been studied. Introduction of LNA monomers around the functionalised 2'-amino-DNA modifications results in reversal of the affinity-decreasing effect of the latter. This represents a novel general approach for design and synthesis of high-affinity functionalised oligonucleotides for biotechnological or medicinal applications.     

The discovery of glycine and related amino acid-based factor Xa inhibitors

Herein, we report on the identification of three potent glycine and related amino acid-based series of FXa inhibitors containing a neutral P1 chlorophenyl pharmacophore. A X-ray crystal structure has shown that constrained glycine derivatives with optimized N-substitution can greatly increase hydrophobic interactions in the FXa active site. Also, the substitution of a pyridone ring for a phenylsulfone ring in the P4 sidechain resulted in an inhibitor with enhanced oral bioavailability.