Limited seed retention during winter inhibits vegetation establishment in spring,affecting lateral marsh expansion capacity

Coastal systems worldwide deliver vital ecosystem services, such as biodiversity, carbon sequestration, and coastal protection. Effectivity of these ecosystem services increases when vegetation is present. Understanding the mechanisms behind vegetation establishment in bio‐geomorphic systems is necessary to understand their ability to recover after erosive events and potential adaptations to climate change. In this study, we examined how seed availability affects vegetation establishment in the salt marsh–intertidal flat transition zone: the area with capacity for lateral marsh expansion. This requires vegetation establishment; therefore, seed availability is essential. In a 6‐month field experiment, we simulated a before and after winter seed dispersal at two locations, the salt‐marsh vegetation edge and the intertidal flat, and studied seed retention, the seed bank, and the seed viability of three pioneer marsh species: Salicornia procumbens, Aster tripolium, and Spartina anglica. During winter storm conditions, all supplied seeds eroded away with the sediment surface layer. After winter, supplied seeds from all three species were retained, mostly at the surface while 9% was bioturbated downwards. In the natural seed bank, A. tripolium and S. anglica were practically absent while S. procumbens occurred more frequently. The viability of S. procumbens seeds was highest at the surface, between 80% and 90%. The viability quickly decreased with depth, although viable S. procumbens seeds occurred up to 15 cm depth. Only when seeds were supplied after winter, many S. procumbens and some S. anglica individuals did establish successfully in the transition zone. Viable seed availability formed a vegetation establishment threshold, even with a local seed source. Our results suggest that, although boundary conditions such as elevation, inundation, and weather conditions were appropriate for vegetation establishment in spring, the soil surface in winter can be so dynamic that it limits lateral marsh expansion. These insights can be used for designing effective nature‐based coastal protection.     

Carbonic anhydrases: from biomedical applications of the inhibitors and activators to biotechnological use for CO2 capture

Abstract

Context: Asthma is multifaceted disease where many targets contribute towards its development and progression. Among these, adenosine receptor subtypes play a major role.

Objective: MCD-KV-10, a novel thiazolo-thiophene was designed and evaluated pre-clinically for its implication in management of asthma.

Materials and methods: This compound showed good affinity and selectivity towards A_2A/A₃ adenosine receptor (AR) subtypes. Furthermore, MCD-KV-10 was evaluated for in vitro lipoxygenase inhibition activity; in vivo mast cell stabilization potential and in vivo anti-asthmatic activity was done in ovalbumin-induced airway inflammation model in guinea pigs.

Results: The compound showed good (>57%) inhibition of lipoxygenase enzyme and also effectively protected mast cell degranulation (>63%). The compound showed good anti-asthmatic activity as inferred from the in vivo studies.

Discussion: These results indicate that MCD-KV-10 has an inhibitory effect on airway inflammation.

Conclusion: Though, we have identified a potential candidate for management of asthma, further mechanistic studies are needed.     

Variation in Polyphenolic Profiles,Antioxidant and Antimicrobial Activity of Different Achillea Species as Natural Sources of Antiglycative Compounds

A comparative study was carried out on the methanolic extracts from six Achillea species and the examined polyphenols from these plants on the formation of advanced glycation end‐products (AGE) in vitro. A. pachycephala which was richer in flavonoids (15 mg quercetin/g W) and phenolics (111.10 mg tannic acid/g DW) with substantial antioxidant activity (IC₅₀ = 365.5 μg/ml) presented strong anti‐AGE properties. Chlorogenic acid, luteolin, quercetin and caffeic acid were identified as the major polyphenols in the extracts by HPLC. In general, polyphenolic content follows the order of A. pachycephalla > A. nobilis > A. filipendulina > A. santolina > A. aucheri > A. millefolium. Most extracts exhibited marked anti‐AGE ability in the bovine serum albumin (BSA)/methylglyoxal (MG) system, though A. pachycephala showed the highest potential. The formation of AGEs was assessed by monitoring the production of fluorescent products and circular dichroism (CD) spectroscopy. Diminution in free radical production (assessed by 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) assays) is discussed as potential mechanism for delay or reduced AGE. The results demonstrate the antiglycative, antioxidant and antimicrobial potential of Achillea species which can be attributed to polyphenols content and the effectiveness on generation of AGEs, thus Achillea species can be considered as natural sources for slowing down glycation related diseases.     

Antagonist binding and induced conformational dynamics of GPCR A2A adenosine receptor

The A_2A adenosine receptor (A_2AAR) is a unique G‐protein coupled receptor (GPCR), because besides agonist, its antagonist could also lead to therapeutic relevance. Based on A_2AAR‐antagonist crystal structure, we have studied the binding mechanism of two distinct antagonists, ZM241385 and KW6002, and dynamic behaviors of A_2AAR induced by antagonist binding. Key residues interacting with both antagonists and residues specifically binding to one of them are identified. ZM241385 specifically bound to S67^2.65, M177^5.38, and N253^6.55, while KW6002 binds to F62^2.60, A81^3.29, and H264^7.29. Moreover, interactions with L167^5.28 are found for both antagonists, which were not reported in agonist binding. The dynamic behaviors of antagonist bound holo‐A_2AARs were found to be different from the apo‐A_2AAR in three typical functional switches, (i) the “ionic lock” was in equilibrium between formation and breakage in apo‐A_2AAR, but stayed broken in holo‐A_2AARs; (ii) the “rotamer toggle switch,” T88^3.36/F242^6.44/W246^6.48, adopted different rotameric conformations in apo‐A_2AAR and holo‐A_2AARs; (iii) apo‐A_2AAR preferred α‐helical intracellular loop (IC)2 and flexible IC3, while holo‐A_2AARs had a flexible IC2 and α‐helical IC3. Our results indicated that antagonist binding induced different conformational rearrangements of these characteristic functional switches in apo‐A_2AAR and holo‐A_2AARs. Proteins 2013; 81:1399–1410. © 2013 Wiley Periodicals, Inc.     

Limonene-induced activation of A2A adenosine receptors reduces airway inflammation and reactivity in a mouse model of asthma

Animal models of asthma have shown that limonene, a naturally occurring terpene in citrus fruits, can reduce inflammation and airway reactivity. However, the mechanism of these effects is unknown. We first performed computational and molecular docking analyses that showed limonene could bind to both A_2A and A_2B receptors. The pharmacological studies were carried out with A_2A adenosine receptor knock-out (A_2AKO) and wild-type (WT) mice using ovalbumin (OVA) to generate the asthma phenotype. We investigated the effects of limonene on lung inflammation and airway responsiveness to methacholine (MCh) and NECA (nonselective adenosine analog) by administering limonene as an inhalation prior to OVA aerosol challenges in one group of allergic mice for both WT and KO. In whole-body plethysmography studies, we observed that airway responsiveness to MCh in WT SEN group was significantly lowered upon limonene treatment but no effect was observed in A_2AKO. Limonene also attenuated NECA-induced airway responsiveness in WT allergic mice with no effect being observed in A_2AKO groups. Differential BAL analysis showed that limonene reduced levels of eosinophils in allergic WT mice but not in A_2AKO. However, limonene reduced neutrophils in sensitized A_2AKO mice, suggesting that it may activate A_2B receptors as well. These data indicate that limonene-induced reduction in airway inflammation and airway reactivity occurs mainly via activation of A_2AAR but A_2B receptors may also play a supporting role.

     

Elevated ozone induces jasmonic acid defense of tomato plants and reduces midgut proteinase activity in Helicoverpa armigera

As a consequence of membrane lipid peroxidation, foliar defense compounds are changed by elevated ozone (O₃), which in turn affects the palatability and performance of insect herbivores. The induced defense of two tomato [Solanum esculentum L. (Solanaceae)] genotypes, namely jasmonic acid (JA) pathway‐deficient mutant spr2 and its wild‐type control, was studied in response to cotton bollworm, Helicoverpa armigera Hübner (Lepidoptera: Noctuidae), as well as the digestive adaptation of these insects under elevated O₃ in open‐top field chambers. Our data indicated that elevated O₃ increased foliar JA and salicylic acid (SA) levels simultaneously and up‐regulated proteinase inhibitors (PIs) and lipoxidase activities in wild‐type plants, regardless of H. armigera infestation. In contrast, only the O₃+H. armigera treatment increased free SA levels in spr2 plants, but did not affect JA level or PI activities. Additionally, the lower activity of midgut digestive enzymes, including active alkaline trypsin‐like enzyme and chymotrypsin‐like enzyme, was observed in the midgut of cotton bollworms after they consumed wild‐type plants treated for 2 h with elevated O₃. With temporary increases at 8 h, all four digestive enzymes of interest in the insect midgut dropped when they were fed with wild‐type plants under elevated O₃ treatment. Increases in atmospheric O₃ are thought to increase JA signaling and consequently reduce the activities of midgut digestive enzymes in H. armigera, therefore enhancing plant resistance against insect herbivores.     

Jasmonate‐mediated stomatal closure under elevated CO2 revealed by time‐resolved metabolomics

Foliar stomatal movements are critical for regulating plant water loss and gas exchange. Elevated carbon dioxide (CO₂) levels are known to induce stomatal closure. However, the current knowledge on CO₂ signal transduction in stomatal guard cells is limited. Here we report metabolomic responses of Brassica napus guard cells to elevated CO₂ using three hyphenated metabolomics platforms: gas chromatography‐mass spectrometry (MS); liquid chromatography (LC)‐multiple reaction monitoring‐MS; and ultra‐high‐performance LC‐quadrupole time‐of‐flight‐MS. A total of 358 metabolites from guard cells were quantified in a time‐course response to elevated CO₂ level. Most metabolites increased under elevated CO₂, showing the most significant differences at 10 min. In addition, reactive oxygen species production increased and stomatal aperture decreased with time. Major alterations in flavonoid, organic acid, sugar, fatty acid, phenylpropanoid and amino acid metabolic pathways indicated changes in both primary and specialized metabolic pathways in guard cells. Most interestingly, the jasmonic acid (JA) biosynthesis pathway was significantly altered in the course of elevated CO₂ treatment. Together with results obtained from JA biosynthesis and signaling mutants as well as CO₂ signaling mutants, we discovered that CO₂‐induced stomatal closure is mediated by JA signaling.     

Jasmonoyl‐l‐isoleucine hydrolase 1 (JIH1) regulates jasmonoyl‐l‐isoleucine levels and attenuates plant defenses against herbivores

For most plant hormones, biological activity is suppressed by reversible conjugation to sugars, amino acids and other small molecules. In contrast, the conjugation of jasmonic acid (JA) to isoleucine (Ile) is known to enhance the activity of JA. Whereas hydroxylation and carboxylation of JA‐Ile permanently inactivates JA‐Ile‐mediated signaling in plants, the alternative deactivation pathway of JA‐Ile by its direct hydrolysis to JA remains unstudied. We show that Nicotiana attenuata jasmonoyl‐l ‐isoleucine hydrolase 1 (JIH1), a close homologue of previously characterized indoleacetic acid alanine resistant 3 (IAR3) gene in Arabidopsis, hydrolyzes both JA‐Ile and IAA‐Ala in vitro. When the herbivory‐inducible NaJIH1 gene was silenced by RNA interference, JA‐Ile levels increased dramatically after simulated herbivory in irJIH1, compared with wild‐type (WT) plants. When specialist (Manduca sexta) or generalist (Spodoptera littoralis) herbivores fed on irJIH1 plants they gained significantly less mass compared with those feeding on wild‐type (WT) plants. The poor larval performance was strongly correlated with the higher accumulation of several JA‐Ile‐dependent direct defense metabolites in irJIH1 plants. In the field, irJIH1 plants attracted substantially more Geocoris predators to the experimentally attached M. sexta eggs on their leaves, compared with empty vector plants, which correlated with higher herbivory‐elicited emissions of volatiles known to function as indirect defenses. We conclude that NaJIH1 encodes a new homeostatic step in JA metabolism that, together with JA and JA‐Ile‐hydroxylation and carboxylation of JA‐Ile, rapidly attenuates the JA‐Ile burst, allowing plants to tailor the expression of direct and indirect defenses against herbivore attack in nature.     

Regulation of adenosine receptors expression in rat B lymphocytes by insulin

Development of diabetes is associated with altered expression of adenosine receptors (ARs). Some of these alterations might be attributed to changes in insulin concentration. This study was undertaken to investigate the possible insulin effect on ARs level, and to determine the signaling pathway utilized by insulin to regulate the expression of ARs in rat B lymphocytes. Western blot analysis of B lymphocytes protein extracts indicated that all four ARs were present at detectable levels in the cells cultured for 24 h without insulin (≤10^?11 M), although the protein band of A_2A‐AR was barely visible. Inclusion of insulin (10^?8 M) in the culture medium resulted in an increase of A₁‐AR and A_2A‐AR protein levels and a significant decrease of A_2B‐AR protein, whereas the protein level of A₃‐AR remained unchanged. Alterations in the ARs protein content were accompanied by changes in the ARs mRNA levels. Increase of the insulin concentration from 10^?11 to 10^?8 M resulted in 50% decrease of A_2B‐AR mRNA level and two‐, and threefold increase of A₁‐AR and A_2A‐AR mRNA levels, respectively. Pretreatment of B cells with cycloheximide completely blocked the insulin action on A₁‐AR and A_2A‐AR mRNA, but not on A_2B‐AR expression. Detailed pharmacological analysis demonstrated that insulin‐induced A₁‐AR and A_2A‐AR mRNA expression through the Ras/Raf‐1/MEK/ERK pathway. The insulin effect on A_2B‐AR expression was blocked by p38 MAP kinase inhibitor (SB 203580). Concluding, elevated insulin concentration differentially affects the expression of ARs in B lymphocytes in a fashion that might enhance the various immunomodulatory effects of adenosine. J. Cell. Biochem. 109: 396–405, 2010. © 2009 Wiley‐Liss, Inc.     

Gender Effects on Adrenergic Receptor Expression and Lipolysis in White Adipose Tissue of Rats

Objective: To investigate the effects of short‐term (15 days) cafeteria‐diet feeding on the expression of α‐ and β‐adrenergic receptors (AR) and its association with lipolytic stimulation in isolated retroperitoneal white adipocytes. Research Methods and Procedures: Six female and 6 male Wistar rats (4 weeks old) were fed a cafeteria diet plus standard diet for 15 days. The remaining 12 age‐ and sex‐matched rats received a standard diet only. White retroperitoneal adipose tissue was isolated and used for the determination of both α₂ and β‐AR expression and for in vitro studies of lipolytic activity. Results: In female control rats, we found higher lipolytic capacities located at the postreceptor level and a lower α₂/β₃‐AR ratio than male rats. Cafeteria‐diet feeding for 15 days decreased lipolytic activity in both male and female rats and altered the α_2A‐ and β₃‐AR protein levels with an increase of α_2A‐AR in males and a β₃‐AR decrease in females. Discussion: Our results indicate that a 15‐day cafeteria‐diet feeding induced an increase in the α₂/β₃‐AR balance and impaired adipose tissue lipolytic activity, which was higher in males and may contribute to the development of increased fat mass. The higher functionality of α₂‐AR, together with the minor role developed by β₃‐AR and lower lipolytic capacities located at the postreceptor level in cafeteria‐diet‐fed male rats compared with female rats, may be responsible for the gender‐dependent differences observed in this study.     

Elevated CO2 affects photosynthetic responses in canopy pine and subcanopy deciduous trees over 10 years: a synthesis from Duke FACE

Leaf responses to elevated atmospheric CO₂ concentration (C_a) are central to models of forest CO₂ exchange with the atmosphere and constrain the magnitude of the future carbon sink. Estimating the magnitude of primary productivity enhancement of forests in elevated C_a requires an understanding of how photosynthesis is regulated by diffusional and biochemical components and up‐scaled to entire canopies. To test the sensitivity of leaf photosynthesis and stomatal conductance to elevated C_a in time and space, we compiled a comprehensive dataset measured over 10 years for a temperate pine forest of Pinus taeda, but also including deciduous species, primarily Liquidambar styraciflua. We combined over one thousand controlled‐response curves of photosynthesis as a function of environmental drivers (light, air C_a and temperature) measured at canopy heights up to 20 m over 11 years (1996–2006) to generate parameterizations for leaf‐scale models for the Duke free‐air CO₂ enrichment (FACE) experiment. The enhancement of leaf net photosynthesis (A_net) in P. taeda by elevated C_a of +200 μmol mol^?1 was 67% for current‐year needles in the upper crown in summer conditions over 10 years. Photosynthetic enhancement of P. taeda at the leaf‐scale increased by two‐fold from the driest to wettest growing seasons. Current‐year pine foliage A_net was sensitive to temporal variation, whereas previous‐year foliage A_net was less responsive and overall showed less enhancement (+30%). Photosynthetic downregulation in overwintering upper canopy pine needles was small at average leaf N (N_area), but statistically significant. In contrast, co‐dominant and subcanopy L. styraciflua trees showed A_net enhancement of 62% and no A_net–N_area adjustments. Various understory deciduous tree species showed an average A_net enhancement of 42%. Differences in photosynthetic responses between overwintering pine needles and subcanopy deciduous leaves suggest that increased C_a has the potential to enhance the mixed‐species composition of planted pine stands and, by extension, naturally regenerating pine‐dominated stands.     

Silencing of OPR3 in tomato reveals the role of OPDA in callose deposition during the activation of defense responses against Botrytis cinerea

Cis‐(+)‐12‐oxo‐phytodienoic acid (OPDA) is likely to play signaling roles in plant defense that do not depend on its further conversion to the phytohormone jasmonic acid. To elucidate the role of OPDA in Solanum lycopersicum (tomato) plant defense, we have silenced the 12‐oxophytodienoate reductase 3 (OPR3) gene. Two independent transgenic tomato lines (SiOPR3‐1 and SiOPR3‐2) showed significantly reduced OPR3 expression upon infection with the necrotrophic pathogen Botrytis cinerea. Moreover, SiOPR3 plants are more susceptible to this pathogen, and this susceptibility is accompanied by a significant decrease in OPDA levels and by the production of JA‐Ile being almost abolished. OPR3 silencing also leads to a major reduction in the expression of other genes of the jasmonic acid (JA) synthesis and signaling pathways after infection. These results confirm that in tomato plants, as in Arabidopsis, OPR3 determines OPDA availability for JA biosynthesis. In addition, we show that an intact JA biosynthetic pathway is required for proper callose deposition, as its pathogen‐induced accumulation is reduced in SiOPR3 plants. Interestingly, OPDA, but not JA, treatment restored basal resistance to B. cinerea and induced callose deposition in SiOPR3‐1 and SiOPR3‐2 transgenic plants. These results provide clear evidence that OPDA by itself plays a major role in the basal defense of tomato plants against this necrotrophic pathogen.