Changes in the δ13C values of trees during a tropical rainy season: some effects in addition to diffusion and carboxylation by rubisco?

The d13C values of deciduous and evergreen tree leaves were compared in open and closed- canopy environments throughout a rainy season in Panamá. Newly emerging leaves had higher d13C values than older leaves of all seedlings and trees at all dates sampled. This was apparently not caused by a decline in water use efficiency as leaves develop because instantaneous ci/ca was significantly higher in newly emerging than in expanded leaves on the same twigs of trees in the field as well as on seedlings growing in a controlled, unchanging environment. Higher d13C values in newly emerging leaves occurred across diverse environmental comparisons. For example, leaves emerging during the rainy season had higher d13C values than corresponding mature leaves that had emerged both during the dry season and when water was abundant. The early enrichment in 13C may thus reflect the translocation of carbon to initiate a new leaf. Furthermore, the lack of sensitivity of this enrichment to a microclimate suggests that it might be the result of processes that occur after carbon fixation by Rubisco. Other changes in d13C values as leaves developed may also have resulted from carbon translocation processes. Foliar d13C decreased significantly after most of the leaf biomass of the deciduous Apeiba membranacea had developed. The d13C values of the evergreen Cecropia insignis were lower in the open canopy than in closed-canopy forests at the end of the rainy season. These findings suggest that the d13C values of leaves can yield ecological information about the allocation of carbon within trees.     

3β-Hydroxysteroid dehydrogenase expressed by gut microbes degrades testosterone and is linked to depression in males

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Are Seasonal Dormancy Patterns in Arabidopsis thaliana Regulated by Changes in Seed Sensitivity to Light, Nitrate and Gibberellin?

Imbibed seeds of Arabidopsis thaliana (L.) Heynh., passed annuallythrough a pattern of changes in dormancy. Dormancy was brokenin summer and re-induced in autumn-winter. A second small germinationflush occurred in early spring. The role of sensitivity to light,nitrate and gibberellins (GAs) in regulating annual dormancypatterns and germination was studied with the use of GA-deficient(gal-2) and wild-type seeds. Dark-incubated seeds were exposedto a natural temperature regime for periods up to 18 monthsand at regular intervals germination capacity of portions ofseeds was tested at laboratory conditions. Germination datafitted as logistic dose response curves showed that sensitivityto light varied with the seasons in both genotypes. From interpretationof curve parameters, it is proposed that the observed sensitivitychanges involve alterations in the number of receptors, in thebinding characteristics of the receptors and/or in the responsechain initiated by ligand-receptor interaction. In this responsechain GA biosynthesis is stimulated (wild type) and sensitivityto GAs is enhanced (wild type, gal -2). GA sensitivity is alsodirectly influenced by temperature, thus without the interferenceof light. However, the significance of direct regulation ofGA requirement seemed to diminish with prolonged incubationoutdoors, whereas reversible changes in light sensitivity remainedclear. Therefore, we propose that seasonal dormancy patternsare mainly regulated by changes in sensitivity to light. GAsensitivity contributes to this pattern but is not primarilycontrolling dormancy. The GA requirement for germination isobvious as gal-2 seeds did not germinate at any time of theyear when deprived of applied GAs. However, GA biosynthesisis not required for dormancy control, as a dormancy patternwas also observed in the absence of the capacity to synthesizeGAs. Nitrate or sensitivity to nitrate did not contribute tothe regulation of dormancy and germination of this species.Copyright1994, 1999 Academic Press Arabidopsis thaliana (L.) Heynh., curve fitting, dormancy, fluence response curve, germination, gibberellin, gibberellin dose response curve, hormone mutant, light, mouse-ear-cress, nitrate, phytochrome, receptor, seasonal dormancy pattern, sensitivity     

A PCR-based method to test for the presence or absence of β-conglycinin α′- and α-subunits in soybean

The soybean cultivar Yumeminori, which lacks the α′- and α-subunits of β-conglycinin, carries both naturally occurring and induced mutations. While the cause of the natural mutation resulting in the α′-subunit deficiency has been determined, the induced mutation in the CG-2 gene encoding the α-subunit has not been characterized at the molecular level. In this study, we identified a four base pair insertion in the first exon of CG-2, which introduced a premature stop codon. The insertion co-segregated with the lack of α-subunit, indicating that this mutation is the cause of the α-subunit deficiency. A multiplex PCR method of testing for the presence or absence of α′- and α-subunits was developed based on the sequences of mutated and wild-type alleles. This PCR-based test was also capable of detecting the presence of wild-type genes when Yumeminori DNA samples were contaminated with wild-type DNA at levels of 0.2% or greater. Thus, this method will be useful both for marker-assisted selection in soybean breeding programs, and for seed purity tests in food industries.     

Changes in stream chemistry and biology in response to reduced levels of acid deposition during 1987–2003 in the Neversink River Basin,Catskill Mountains

Atmospheric acid deposition has decreased in the northeastern United States since the 1970s, resulting in modest increases in pH, acid-neutralizing capacity (ANC), and decreases in inorganic monomeric aluminum (Al_IM) concentrations since stream chemistry monitoring began in the 1980s in the acid-sensitive upper Neversink River basin in the Catskill Mountains of New York. Stream pH has increased by 0.01 units/year during 1987–2003 at three sites in the Neversink basin as determined by Seasonal Kendall trend analysis. In light of this observed decrease in stream acidity, we sampled 12 stream sites within the Neversink River watershed for water chemistry, macroinvertebrates, fish, and periphytic diatoms in 2003 to compare with a similar data set collected in 1987. Metrics and indices that reflect sensitivity to stream acidity were developed with these biological data to determine whether changes in stream biota over the intervening 16 years parallel those of stream chemistry. Statistical comparisons of data on stream chemistry and an acid biological assessment profile (Acid BAP) derived from invertebrate data showed no significant differences between the two years. For pH and ANC, however, values in 2003 were generally lower than those in 1987; this difference likely resulted from higher streamflow in summer 2003. Despite these likely flow-induced changes in summer 2003, an ordination and cluster analysis of macroinvertebrate taxa based on the Acid BAP indicated that the most acidic sites in the upstream half of the East Branch Neversink River form a statistically significant separate cluster consistent with less acidic stream conditions. This analysis is consistent with limited recovery of invertebrate species in the most acidic reaches of the river, but will require additional improvement in stream chemistry before a stronger conclusion can be drawn. Data on the fish and periphytic diatom communities in 2003 indicate that slimy sculpin had not extended their habitat to upstream reaches that previously were devoid of this acid-intolerant species in 1987; a diatom acid-tolerance index indicates continued high-acid impact throughout most of the East Branch and headwaters of the West Branch Neversink River.     

β-1,3-glucanase and chitinase activities in winter triticales during cold hardening and subsequent infection by Microdochium nivale

The accumulation of pathogenesis-related proteins such as β-1,3-glucanases and chitinases was studied in cold induced snow mould resistance in two Polish cultivars of winter triticale, cv. Hewo and cv. Magnat that substantially differ in resistance to Microdochium nivale. The plants were pre-hardened at 12°C for 10 days and hardened at 4°C for 28 days. Subsequently, cold hardened plants were inoculated with fungal mycelium (M. nivale) and incubated at 4°C for 7 days in dark. Cold acclimatisation resulted in suppression of the total glucanase and chitinases activities in the resistant Hewo as well as sensitive Magnat cultivars that possibly coincides with altered metabolism. However, upon infection with M. nivale the chitinases were markedly induced in the cv. Hewo. At the same time, total β-1,3 glucanases activities did not seem to be affected by fungus in any of the tested triticale cultivars. The pattern and/or the activity of chitinases in plants might be indicative for the resistance/susceptibility against M. nivale.     

Changes in Root Exudates and Root Proteins in Groundnut–Pseudomonas sp. Interaction Contribute to Root Colonization by Bacteria and Defense Response of the Host

Journal of Plant Growth Regulation - Selection and application of rhizobacteria, for improved plant health will benefit from a complete understanding of the plant–bacteria interaction. Root...     

HIF-1α drives resistance to ferroptosis in solid tumors by promoting lactate production and activating SLC1A1

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Lack of correlation between constitutive and induced resistance to a herbivore in crucifer plants: real or flawed by experimental methods?

The correlation between constitutive and induced resistance to herbivores in plants has long been of interest to evolutionary biologists, and various approaches to determining levels of resistance have been used in this field of research. In this study, we examined the relationship between constitutive and induced resistance to the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), in 11 closely related species of wild crucifers. We assessed the survival, development, and reproduction of the test insects and calculated their intrinsic rate of increase as an indicator of constitutive and induced resistance for the plants. We used larvae of P. xylostella and jasmonic acid as elicitors of the induced response. We failed to find a correlation between constitutive and induced resistance in these crucifer plants when the induction of resistance was initiated by either herbivory or jasmonic acid application. Analysis of the results suggests that the failure to detect a relationship between the two types of resistance could be caused by flaws in measuring constitutive resistance, which was apparently confounded with induced resistance. We discuss the difficulties and pitfalls in measuring constitutive resistance and ways to improve the methodology in investigating the relationships between constitutive and induced resistance in plants.     

Genetic relationships between resistance to stalk-tunneling by the European corn borer and cell-wall components in maize population B73×B52

The objective of this study was to assess the relationships among quantitative trait loci (QTL) detected for European corn borer (ECB) tunneling and cell-wall components (CWC) neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL) content in leaf-sheath and stalk tissues in a maize recombinant inbred line population derived from inbred lines B73 and B52. Most of the QTL for ECB resistance (10/13) were at QTL positions for one or more CWC. Of the 12 QTL for NDF and ADF in leaf-sheaths, five for each trait were at or near QTL for ECB tunneling. Four of these five QTL for NDF and ADF mapped to common locations. Four of the eight leaf-sheath ADL QTL were detected in the same genomic regions as ECB QTL. For stalk tissue, four regions contained common/overlapping QTL for ECB tunneling, NDF, and ADF. Six such regions were observed for stalk ADL and ECB tunneling. Seven of the ten QTL associated with both CWC and ECB tunneling contributed to the negative correlations observed between these traits, while relatively few QTL effects were positively correlated. This suggests that while CWC contribute to ECB resistance in this population, other mechanisms and other genes also are involved. Several QTL contributing to the negative correlations between ECB tunneling and CWC in the leaf-sheaths mapped to similar positions as QTL detected in tropical maize populations for resistance to leaf-feeding by Diatraea grandiosella Dyar and Diatraea saccharalis Fabricus. These regions may contain genes involved in the synthesis of cellulose, hemicellulose, and lignin in the leaf-blades and leaf-sheaths of maize.     

Exposure to a maternal n-3 fatty acid-deficient diet during brain development provokes excessive hypothalamic–pituitary–adrenal axis responses to stress and behavioral indices of depression and anxiety in male rat offspring later in life

Brain docosahexaenoic acid (DHA, 22:6n-3) accumulates rapidly during brain development and is essential for normal neurological function. The aim of this study was to evaluate whether brain development was the critical period in which DHA deficiency leads to dysregulation of the hypothalamic–pituitary–adrenal (HPA) axis in response to stress later in life. Rats were exposed to an n-3 fatty acid-deficient diet or the same diet supplemented with fish oil as an n-3 fatty acid-adequate diet either throughout the preweaning period from embryo to weaning at 3 weeks old or during the postweaning period from 3 to 10 weeks old. Exposure to the n-3 fatty acid-deficient diet during the preweaning period resulted, at weaning, in a significant decrease in hypothalamic DHA levels and a reduced male offspring body weight. DHA deficiency during the preweaning period significantly increased and prolonged restraint stress-induced changes in colonic temperature and serum corticosterone levels, caused a significant increase in GABA_A antagonist-induced heart rate changes and enhanced depressive-like behavior in the forced swimming test and anxiety-like behavior in the plus-maze test in later life. These effects were not seen in male rats fed the n-3 fatty acid-deficient diet during the postweaning period. These results suggest that brain development is the critical period in which DHA deficiency leads to excessive HPA responses to stress and elevated behavioral indices of depression and anxiety in adulthood. We propose that these effects of hypothalamic DHA deficiency during brain development may involve a GABA_A receptor-mediated mechanism.     

The tail that wags the dog: p12, the smallest subunit of DNA polymerase δ, is degraded by ubiquitin ligases in response to DNA damage and during cell cycle progression

DNA polymerase δ (Pol δ) is a key enzyme in eukaryotic DNA replication. Human Pol δ is a heterotetramer whose p12 subunit is degraded in response to DNA damage, leading to the in vivo conversion of Pol δ4 to Pol δ3. Two E3 ubiquitin ligases, RNF8 and CRL4^Cdt2, participate in the DNA damage-induced degradation of p12. We discuss how these E3 ligases integrate the formation of Pol δ3 and ubiquitinated PCNA for DNA repair processes. CRL4^Cdt2 partially degrades p12 during normal cell cycle progression, thereby generating Pol δ3 during S phase. This novel finding extends the current view of the role of Pol δ3 in DNA repair and leads to the hypothesis that it participates in DNA replication. The coordinated regulation of licensing factors and Pol δ3 by CRL4^Cdt2 now opens new avenues for control of DNA replication. A parallel study of Pol δ4 and Pol δ3 in Okazaki fragment processing provides evidence for a role of Pol δ3 in DNA replication. We discuss several new perspectives of the role of the 2 forms of Pol δ in DNA replication and repair, as well the significance of the integration of p12 regulation in DNA repair and cell cycle progression.     

High internal resistance to CO2 uptake by submerged macrophytes that use HCO3 −: measurements in air,nitrogen and helium

Previous studies have shown that in water the affinity of submerged macrophytes for CO₂ is higher for species restricted to CO₂ than for species with an additional ability to use bicarbonate. We measured slopes of CO₂ uptake versus CO₂ concentration in the gas phase in air, nitrogen and helium for pairs of species, having or lacking the ability to use bicarbonate, but with similar leaf morphology. For species restricted to CO₂, the slope in nitrogen and helium was 1.5 times and 3.2 times greater than in air. The increased slope in nitrogen results from a suppression of photorespiration. The further increase in helium reflects the increased rate of diffusion of CO₂ and shows that, even in gas, external diffusion through the boundary layer is a significant hindrance to CO₂ uptake. In contrast, in species able to use bicarbonate, the uptake slope was not affected by gas composition, suggesting that photorespiration is absent or photorespired CO₂ is efficiently trapped and that internal resistance is high relative to external resistance. Elodea canadensis specimens grown under high concentrations of CO₂ de-regulated their ability to use bicarbonate, and slopes of CO₂ uptake in helium were significantly greater than in air or nitrogen. Overall, these results are consistent with the notion that while a high affinity for CO₂ will maximise carbon uptake in species restricted to CO₂, for species able to use bicarbonate, a high internal resistance would reduce loss of CO₂ and help maintain high concentrations of CO₂ at the site of fixation. This revised version was published online in August 2006 with corrections to the Cover Date.     

Bacteriophage types of methicillin--resistant Staphylococcus aureus strains isolated in 2005-2006 in the Gdańsk area and their resistance to other antibiotics

The phage type of 38 methicillin--resistant Staphylococcus aureus strains isolated from clinical samples in 5 hospitals in the Gdańsk area in 2005-2007 was determined and antibiotic resistance of obtained phage types was analysed. Phage typing was performed using set of 10 phages as following: MR8, MR12, MR25, 30, 33, 38, M3, M5, 622, 56B. Drug resistance was determined by the disc--diffusion method. There were 12 phage types observed. The most frequent (28.9%) was 56B type which was present in 3 hospitals and in one hospital was found to be predominated. The studied strains were most frequent (23.7%) resistant to erythromycin, clindamycin, ciprofloxacin, trimethoprim/sulfamethoxazole, tetracycline and gentamicin. This resistance pattern predominated in strains belonging to 56B type.     

Xanthomonas campestris pv. campestris lpsI and lpsJ genes encoding putative proteins with sequence similarity to the α- and β-subunits of 3-oxoacid CoA-transferases are involved in LPS biosynthesis

A 2.1-kb SmaI-EcoRI DNA fragment upstream of the xanA and xanB genes of Xanthomonas campestris pv. campestris carries two ORFs encoding putative proteins with sequence similarities to the α- and β-subunits of 3-oxoacid-CoA transferases. The two ORFs were termed lpsI and lpsJ because strains carrying appropriate mutations showed an autoagglutination phenotype and because lipopolysaccharides of these mutant strains were altered according to silver-stained polyacrylamide gels. The monosaccharide composition of the exopolysaccharide xanthan produced by lpsI and lpsJ mutants remained unchanged. Received: 29 March 1997 / Accepted: 21 July 1997     

Changes of inheritance mode and fitness in Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) along with its resistance evolution to Cry1Ac toxin

The changes of inheritance mode and fitness of resistance in Helicoverpa armigera (Hübner) along with its resistance evolution to Cry1Ac toxin were evaluated in the laboratory. The resistance levels reached 170.0-, 209.6- and 2893.3-fold, on selection of the field population in the 16th (BtR-F(16)), 34th (BtR-F(34)) and 87th (BtR-F(87)) generation with artificial diet containing Cry1Ac toxin, respectively. As the resistance levels increased, more larvae feeding on the Bt cotton expressing Cry1Ac toxin survived. Most larvae of BtR-F(87) could develop to the 5th instar and about 3% individuals reached the adult stage. The inheritance of Cry1Ac resistance trait at three resistant levels was autosomal and incompletely recessive, but the degree of dominance decreased as the resistance increased. The resistance was primarily monogenic in BtR-F(16) strain, but polygenic as resistance increased. The relative fitness of H. armigera, measured as a ratio of R(0) (the net replacement rate) of resistant strain divided by R(0) of the susceptible strain, decreased with an increase of the resistance levels, with ratios of 0.79, 0.64 and 0.59 in their respective BtR-F(16), BtR-F(34) and BtR-F(87) strains.     

Phenotypic Adaptation of Tonoplast Fluidity to Growth Temperature in the CAM Plant Kalanchoë daigremontiana Ham. et Per. is Accompanied by Changes in the Membrane Phospholipid and Protein Composition

The present study deals with the phenotypic adaptation of tonoplast fluidity in the CAM plant Kalancho? daigremontiana to changes in growth temperature. Tonoplast fluidity was characterized by measuring fluorescence depolarization in membranes labeled with fluorescent fatty acid analogues and by following formation of eximeres in membranes labeled by eximere-forming fluorophores. With both techniques it was found that exposure of the plants to higher growth temperature compared with the control decreased the fluidity of the tonoplast while exposure to lower growth temperature caused the opposite. Three hours of high temperature treatment (raised from 25°C to 35°C; ``heat shock') were sufficient to decrease the tonoplast fluidity to roughly the same extent as growth under high temperature for 30 days. The phenotypic response of tonoplast fluidity to changes in growth temperature was found only in the complete membrane, not however in the lipid matrix deprived of the membrane proteins. Heat treatments of the plants decreased the lipid/protein ratio while exposure to low temperature (for 30 days) increased it. Heat treatments led to a decrease in the percentage of linolenic acid (C18:3) and linoleic acid (C18:2), heat shock and low temperature treatments induced an increase in the percentage of linoleic acid (C18:3), with concomitant decrease in the percentage of linoleic acid (C18:2). However, in the case of heat shock, increase in linolenic acid concerned mainly monogalactosyldiacylglycerol, while with low temperature treatment linoleic acid increased in phosphatidylcholine. Both treatment of the plants with high and low temperature led to a slight decrease in the contribution of phosphatidylcholine and phosphoethanolamine to the total phospholipid content of the tonoplast. High-temperature treatment of the plants not only decreased the phospholipid/protein ratio in the tonoplast, but also led to the occurrence of a 35 kDa polypeptide in the tonoplast which cross-reacted with an antiserum against the tonoplast H⁺-ATPase holoenzyme. The important role of membrane proteins in bringing about the phenotypic rigidization of the tonoplast was mimicked by reconstitution experiments showing that incorporation of the proteins isolated from the tonoplast into phosphatidylcholine vesicles decreased the fluidity of this membrane system. As to be expected from the analyses in the natural membrane, the degree of this effect depended on the phospholipid/protein ratio. Received: 4 March 1998/Revised: 28 July 1998     

A9C sensitive Cl? - accumulation in A. thaliana root cells during salt stress is controlled by internal and external calcium

The involvement of chloride in salt stress symptoms and salt tolerance mechanisms in plants has been less investigated in the past. Therefore, we studied the salt-induced chloride influx in Arabidopsis expressing the GFP-based anion indicator Clomeleon. High salt concentrations induce two phases of chloride influx. The fast kinetic phase is likely caused by membrane depolarization, and is assumed to be mediated by channels. This is followed by a slower "saturation" phase, where chloride is accumulated in the cytoplasm. Both phases of chloride uptake are dependent on the presence of external calcium. In general: with high [Ca²⁺] less chloride is accumulated in the cytoplasm. Surprisingly, also the internal calcium availability has an impact on chloride transport. A complete block of the second phase of chloride influx is achieved by the anion channel blocker A9C and trivalent cations (La³⁺, Gd³⁺, and Al³⁺). Other channel blockers and diuretics were found to inhibit the process partially. The results suggest that several transporter species are involved here, including electroneutral cation-chloride-cotransporters, and a part of chloride possibly enters the cells through cation channels after salt application.