Predicting leaf traits of herbaceous species from their spectral characteristics

Trait predictions from leaf spectral properties are mainly applied to tree species, while herbaceous systems received little attention in this topic. Whether similar trait–spectrum relations can be derived for herbaceous plants that differ strongly in growing strategy and environmental constraints is therefore unknown. We used partial least squares regression to relate key traits to leaf spectra (reflectance, transmittance, and absorbance) for 35 herbaceous species, sampled from a wide range of environmental conditions. Specific Leaf Area and nutrient‐related traits (N and P content) were poorly predicted from any spectrum, although N prediction improved when expressed on a per area basis (mg/m² leaf surface) instead of mass basis (mg/g dry matter). Leaf dry matter content was moderately to good correlated with spectra. We explain our results by the range of environmental constraints encountered by herbaceous species; both N and P limitations as well as a range of light and water availabilities occurred. This weakened the relation between the measured response traits and the leaf constituents that are truly responsible for leaf spectral behavior. Indeed, N predictions improve considering solely upper or under canopy species. Therefore, trait predictions in herbaceous systems should focus on traits relating to dry matter content and the true, underlying drivers of spectral properties.     

Properties of Haemophilus influenzae mutants that are slightly recombination deficient and carry a mutation in the rec-1 gene region.

The highly recombination-deficient rec-1 mutants of Haemophilus influenzae are, as far as tested, equivalent to recA mutants of Escherichia coli. By selection for mutations in the rec-1 gene of H. influenzae, mutants designated ird (intermediary recombination-deficient) mutants were isolated; these mutants were much less recombination deficient (degree of transformability, 0.2 to 30% of wild-type value) than previously isolated rec-1 mutants (degree of transformability, 0.0001% of wild-type value). The ird mutants were more sensitive to ultraviolet irradiation and mytomycin C treatment than the wild type, but less sensitive than rec-1 mutants. Spontaneous production of phage HP1c1 by lysogenic MC11 cells and prophage induction by mitomycin C or ultraviolet irradiation were the same as in the wild type. In the ird mutants endogenous deoxyribonucleic acid was degraded both spontaneously and after ultraviolet irradiation to the same extent as in the wild type. Examination of one of the ird mutants revealed that recombination could be enhanced by ultraviolet irradiation, possibly because of an increased synthesis of the rec-1 gene product induced by ultraviolet irradiation.     

Engineering Filamentous Fungi for Conversion of d-Galacturonic Acid to l-Galactonic Acid

d-Galacturonic acid, the main monomer of pectin, is an attractive substrate for bioconversions, since pectin-rich biomass is abundantly available and pectin is easily hydrolyzed. l-Galactonic acid is an intermediate in the eukaryotic pathway for d-galacturonic acid catabolism, but extracellular accumulation of l-galactonic acid has not been reported. By deleting the gene encoding l-galactonic acid dehydratase (lgd1 or gaaB) in two filamentous fungi, strains were obtained that converted d-galacturonic acid to l-galactonic acid. Both Trichoderma reesei Δlgd1 and Aspergillus niger ΔgaaB strains produced l-galactonate at yields of 0.6 to 0.9 g per g of substrate consumed. Although T. reesei Δlgd1 could produce l-galactonate at pH 5.5, a lower pH was necessary for A. niger ΔgaaB. Provision of a cosubstrate improved the production rate and titer in both strains. Intracellular accumulation of l-galactonate (40 to 70 mg g biomass⁻¹) suggested that export may be limiting. Deletion of the l-galactonate dehydratase from A. niger was found to delay induction of d-galacturonate reductase and overexpression of the reductase improved initial production rates. Deletion of the l-galactonate dehydratase from A. niger also delayed or prevented induction of the putative d-galacturonate transporter An14g04280. In addition, A. niger ΔgaaB produced l-galactonate from polygalacturonate as efficiently as from the monomer.     

Macroecology meets macroevolution: evolutionary niche dynamics in the seaweed Halimeda

Aim Because of their broad distribution in geographical and ecological dimensions, seaweeds (marine macroalgae) offer great potential as models for marine biogeographical inquiry and exploration of the interface between macroecology and macroevolution. This study aims to characterize evolutionary niche dynamics in the common green seaweed genus Halimeda, use the observed insights to gain understanding of the biogeographical history of the genus and predict habitats that can be targeted for the discovery of species of special biogeographical interest. Location Tropical and subtropical coastal waters. Methods The evolutionary history of the genus is characterized using molecular phylogenetics and relaxed molecular clock analysis. Niche modelling is carried out with maximum entropy techniques and uses macroecological data derived from global satellite imagery. Evolutionary niche dynamics are inferred through application of ancestral character state estimation. Results A nearly comprehensive molecular phylogeny of the genus was inferred from a six‐locus dataset. Macroecological niche models showed that species distribution ranges are considerably smaller than their potential ranges. We show strong phylogenetic signal in various macroecological niche features. Main conclusions The evolution of Halimeda is characterized by conservatism for tropical, nutrient‐depleted habitats, yet one section of the genus managed to invade colder habitats multiple times independently. Niche models indicate that the restricted geographical ranges of Halimeda species are not due to habitat unsuitability, strengthening the case for dispersal limitation. Niche models identified hotspots of habitat suitability of Caribbean species in the eastern Pacific Ocean. We propose that these hotspots be targeted for discovery of new species separated from their Caribbean siblings since the Pliocene rise of the Central American Isthmus.     

Opposing effects of hypoxia on catecholaminergic locus coeruleus and hypocretin/orexin neurons in chick embryos

Terrestrial vertebrate embryos face a risk of low oxygen availability (hypoxia) that is especially great during their transition to air‐breathing. To better understand how fetal brains respond to hypoxia, we examined the effects of low oxygen availability on brain activity in late‐stage chick embryos (day 18 out of a 21‐day incubation period). Using cFos protein expression as a marker for neuronal activity, we focused on two specific, immunohistochemically identified cell groups known to play an important role in regulating adult brain states (sleep and waking): the noradrenergic neurons of the Locus Coeruleus (NA‐LC), and the Hypocretin/Orexin (H/O) neurons of the hypothalamus. cFos expression was also examined in the Pallium (the avian analog of the cerebral cortex). In adult mammalian brains, cFos expression changes in a coordinated way in these areas. In chick embryos, oxygen deprivation simultaneously activated NA‐LC while deactivating H/O‐producing neurons; it also increased cFos expression in the Pallium. Activity in one pallial primary sensory area was significantly related to NA‐LC activity. These data reveal that at least some of the same neural systems involved in brain‐state control in adults may play a central role in orchestrating prenatal hypoxic responses, and that these circuits may show different patterns of coordination than seen in adults. © 2014 Wiley Periodicals, Inc. Develop Neurobiol 74: 1030–1037, 2014     

Habitat selection by wintering male and female Snowy Owls on the Canadian prairies in relation to prey abundance and a competitor,the Great Horned Owl

Birds overwintering at high latitudes may find it challenging to meet their energy budgets when thermoregulatory costs are high and food availability is low. Snowy Owls (Bubo scandiacus), like most raptors, exhibit reversed sexual size dimorphism, so , if availability of high‐quality (food‐rich) habitats is limited, we predicted that larger and dominant females would use better ‐ quality habitat than males. During the winters of 2014–2015 and 2015–2016 in Saskatchewan , where many Snowy Owls overwinter annually, we measured prey (small mammal) abundance in fields with four types of cover, including cut stalks (stubble) of canola, grain and legume crops, and pasture, and related this estimate of quality to habitat selection by males and females. Small mammal abundance varied annually , but not among the three types of crop stubble. However, prey were less abundant in pastures than in the three types of crop cover in one of three years. Biweekly surveys of owls conducted during the two winters along a 60 ‐ km transect revealed weak selection for legume fields, especially by males. The home ranges of nine females with transmitters included proportionally less canola stubble than those of eight males with transmitters. Within home ranges, males avoided canola stubble and tended to use legume fields more, whereas females used all four habitat types in proportion to availability. Fewer Snowy Owls than expected were observed at locations along the transect within 800 m of Great Horned Owls (Bubo virginianus) and their associated habitats , suggesting that Snowy Owls also avoided these potential competitors on the landscape. Our results suggest that larger females outcompete smaller male Snowy Owls for home ranges in preferred habitat with less canola stubble because stubble‐free legume fields provide easier access to prey than canola fields with numerous rigid stalks.     

Iodoazomycin riboside (1-(5'-iodo-5'-deoxyribofuranosyl)-2-nitroimidazole), a hypoxic cell marker. I. Synthesis and in vitro characterization

Misonidazole (MISO), a selective radiosensitizer of hypoxic cells, forms adducts with cellular biomolecules with rates which are 30-50 X higher under hypoxic as compared to aerobic conditions of incubation. This technique of sensitizer adduct formation was proposed as a possible means of measuring the hypoxic fraction of solid tumors by noninvasive procedures. Iodoazomycin riboside (5'-IAZR) and 5'-[125I]AZR were synthesized and chemically characterized. Measurements of in vitro cytotoxicity and radiosensitizing ability with EMT-6 tumor cells in vitro indicated that 5'-IAZR is approximately 3 X more toxic and effective than is azomycin riboside (AZR) and approximately 10 X more toxic and effective than is MISO. 5'-[125I]AZR was shown to selectively bind to hypoxic EMT-6 cells at rates which were 2.5-3 X faster than those of MISO. The absolute rates of binding of 5'-IAZR to hypoxic cells at concentrations of 10-100 microM are the highest observed in this laboratory for any hypoxic cell radiosensitizer tested to date. These data suggest that 5'-IAZR, when labeled with an appropriate radioisotope (e.g., 131I), might be a useful marker for hypoxic cells in solid tumors amenable to noninvasive detection. Additional studies with animal tumor models appear to be warranted.     

Synthesis,In Vitro Biological Stability,and Anti-HIV Activity of 5-Halo (or Methoxy)-6-Alkoxy (Azido or Hydroxy)-5,6-Dihydro-2′,3′-Didehydro-3′-Deoxythymidine Diastereomers as Potential Prodrugs of 2′,3′-Didehydro-3′-deoxythymidine (D4T)

Abstract

A new class of 5-halo (or methoxy)-6-alkoxy (azido or hydroxy)-5,6-dihydro-2′,3′-didehydro-3′-deoxythymidines (4–17) were investigated as potential anti-AIDS drugs. These 5,6-dihydro derivatives, which are also potential prodmgs of 2′,3′-didehydro-3′-deoxythymidine (D4T) were designed to have properties which would enhance their duration of action, lipophilicity and cephalic delivery to the central nervous system. The 5,6-dihydro derivatives of D4T (4–15), which differ in configuration at the C-5 and C-6 positions, were synthesized by the regiospecific addition of XR (X = Br, Cl, I; R = OMe, OEt, N₃, OH) to the 5,6-olefinic bond of D4T. These 5,6-disubstituted-5,6-dihydro analogs of D4T are more lipophilic (P = 0.70 – 4.0 range) than D4T (P = 0.12) and are stable to E. coli thymidine phosphorylase. Regeneration of the 5,6-olefinic bond to give D4T, upon incubation of the 5-bromo- and 5-iodo-6-methoxy-5,6-dihydro derivatives (6, 7, 10, 11) with glutathione or a mouse liver soluble enzyme fraction, was extensive (50–95%). The most potent anti-HIV-1 agents, 5-iodo-6-methoxy (10, 11), 5-bromo-6-azido (14, 15) and 5-methoxy-6-hydroxy (16, 17) derivatives of D4T, exhibited anti-HIV activities comparable to D4T.

     

Differential regulation of the secretion of luteinizing hormone and follicle-stimulating hormone around the time of ovulation in the bitch

Plasma concentrations of luteinizing hormone (LH) and follicle stimulating hormone (FSH) were determined 3-6 times daily in six Beagle bitches from the start of the follicular phase until 5 d after the estimated day of ovulation. The aim of the study was to gain more detailed information regarding the changes in and the temporal relation between these hormones around the time of ovulation. In all bitches, the pre-ovulatory LH surge was accompanied by a pre-ovulatory FSH surge. The mean duration of the pre-ovulatory FSH surge (110 +/- 8 h) was significantly longer than that of the pre-ovulatory LH surge (36 +/- 5 h). The FSH surge started concomitantly with the pre-ovulatory LH surge in four bitches, and 12 h before the start of the LH surge in the other two bitches. The pre-ovulatory LH surge had a bifurcated pattern in four bitches. The mean plasma LH concentration before (1.9 +/- 0.4 microg/L) and after (1.9 +/- 0.3 microg/L) the pre-ovulatory LH surge were similar. The mean plasma FSH concentration during the period 72-28 h before the pre-ovulatory LH surge (1.6 +/- 0.3 U/L) was lower (P < 0.001) than that during the period 100-144 h after the pre-ovulatory LH surge (3.1 +/- 0.2U/L). In conclusion, this study demonstrated concurrent pre-ovulatory surges of FSH and LH and provided more evidence for differential regulation of the secretion of FSH and LH.     

Isolation and characterization of polymorphic microsatellite loci for the northern flicker (Colaptes auratus; Aves)

To investigate the mating system of northern flickers (Colaptes auratus), we developed primers for 14 microsatellite loci and screened them in 68 unrelated adults and their offspring. All markers were highly polymorphic with 9 to +36 alleles per locus. One marker was Z‐chromosome linked; one marker exceeded the size standard range and could not be analysed further. We checked the other 12 markers for Mendelian inheritance in 36 broods for which the social parents were known. Seven markers showed evidence for the presence of null alleles, and three of those showed significant deviation from Hardy–Weinberg equilibrium. Markers were generally unlinked.