Cilia and the cell cycle?

A recent convergence of data indicating a relationship between cilia and proliferative diseases, such as polycystic kidney disease, has revived the long-standing enigma of the reciprocal regulatory relationship between cilia and the cell cycle. Multiple signaling pathways are localized to cilia in mammalian cells, and some proteins have been shown to act both in the cilium and in cell cycle regulation. Work from the unicellular alga Chlamydomonas is providing novel insights as to how cilia and the cell cycle are coordinately regulated.     

9-Aminoacridine and dibucaine exhibit competitive interactions and complicated inhibitory effects that interfere with measurements of ΔpH and xanthophyll cycle-dependent Photosystem II energy dissipation

This study concerns measurements and interpretations of the trans-thylakoid membrane pH gradient, pH, and xanthophyll cycle-dependent energy dissipation in Photosystem II (PS II). Compared and contrasted are the concentration-dependent inhibitory effects and interactions between two lipophilic tertiary amines, namely, 9-aminoacridine the pH indicator and dibucaine a local anesthetic reported to inhibit both the pH and xanthophyll cycle deepoxidation. Chlorophyll a fluorescence monitored both electron transport efficiency and xanthophyll cycle-dependent energy dissipation, high-performance liquid chromatography monitored deepoxidase and chloroplast ATPase activities and steady-state fluorescence monitored various activities of the amines in solution. Low concentrations (up to 2 M) of both 9-aminoacridine and dibucaine showed similar fluorescence properties and pH-dependent uptake into thylakoids. Importantly both amines exhibited mutually competitive inhibitory effects with respect to this pH-dependent uptake and fluorescence quenching. The fluorescence yields of both compounds in aqueous solution were strongly quenched by sodium ascorbate, a necessary cofactor for in vitro deepoxidation. Both compounds similarly inhibited several light induced activities including deepoxidation, photosynthetic electron transport and PS II energy dissipation. However, for all these activities 9-aminoacridine was 2 to 5 times more potent. Importantly, 9-aminoacridine inhibited deepoxidation with an I₅₀1 M, a concentration far below that which inhibits the pH, ATP synthesis/hydrolysis or electron transport. The inhibitory effects of both compounds on PS II energy dissipation were exerted at 3 to 5 times lower concentration if added before as opposed to after a saturating level of deepoxidation. This result confirms the important role for deepoxidation in mediating PS II energy dissipation. Compared to 9-aminoacridine and in contrast to similar effects on the light-induced activities, dibucaine exhibited significantly different inhibitory effects on ATPase activity and ATPase mediated PS II energy dissipation. However, we conclude from the more potent inhibition by 9-aminoacridine and the similar inhibitory patterns of all the light-induced activities that neither 9-aminoacridine nor dibucaine possess unique capacities to neutralize the light-mediated pH. DCMU–3-(3,4-dichlorophenyl)-1,1-dimethylurea; DTT–dithiothreitol; f_x–fractional intensity of fluorescence lifetime component x; F()_m–maximal PS II Chl a fluorescence intensity with all Q_A reduced in the absence (presence) of thylakoid membrane energization; F_o–minimal PS II Chl a fluorescence intensity with all Q_A oxi dized; F_s–steady state PS II Chl a fluorescence; HPLC–high performance liquid chromatography; I_(o)–intensity of fluorescence in the presence (absence) of quencher; K_a–association constant between Z (and A) and protonated PS II units; LA–local anesthetic; NaAsc–sodium ascorbate; NR–neutral red; PAM–pulse-amplitude modulation fluorometer; PFD–photon-flux density, mols photons m^-2 s^-1; PS I–Photosystem I; PS II–Photosystem II; [PS II^-+]–concentration of PS II units with inactive/deprotonated (active/protonated ) xanthophyll binding sites; [PS II_tot]–total concentration of PS II units; [PS II⁺-Z]–concentration of PS II units with Z or A bound; Q–fraction of fluorescence intensity that is quenched; Q_max–fraction of fluorescence intensity that is quenched under control conditions; Q_A–primary quinone electron acceptor of PS II; V–violaxanthin; Z–zeaxanthin; 9AA–9-aminoacridine; pH–trans-thylakoid membrane proton gradient; _f–lifetime of Chl a fluorescence     

Do the capacity and kinetics for modification of xanthophyll cycle pool size depend on growth irradiance in temperate trees?

The present study investigated the interaction of growth irradiance (Q_int) with leaf capacity for and kinetics of adjustment of the pool size of xanthophyll cycle carotenoids (sum of violaxanthin, antheraxanthin and zeaxanthin; VAZ) and photosynthetic electron transport rate (J_max) after changes in leaf light environment. Individual leaves of lower‐canopy/lower photosynthetic capacity species Tilia cordata Mill. and upper canopy/higher photosynthetic capacity species Populus tremula L. were either illuminated by additional light of 500–800 µmol m^?2 s^?1 for 12 h photoperiod or enclosed in shade bags. The extra irradiance increased the total amount of light intercepted by two‐fold for the upper and 10–15‐fold for the lower canopy leaves, whereas the shade bags transmitted 45% of incident irradiance. In control leaves, VAZ/area, VAZ/Chl and J_max were positively associated with leaf growth irradiance (Q_int). After 11 d extra illumination, VAZ/Chl increased in all cases due to a strong reduction in foliar chlorophyll, but VAZ/area increased in the upper canopy leaves of both species, and remained constant or decreased in the lower canopy leaves of T. cordata. The slope for VAZ/area changes with cumulative extra irradiance was positively associated with Q_int only in T. cordata, but not in P. tremula. Nevertheless, all leaves of P. tremula increased VAZ/area more than the most responsive leaves of T. cordata. Shading reduced VAZ content only in P. tremula, but not in T. cordata, again demonstrating that P. tremula is a more responsive species. Compatible with the hypothesis of the role of VAZ in photoprotection, the rates of photosynthetic electron transport declined less in P. tremula than in T. cordata after the extra irradiance treatment. However, foliar chlorophyll contents of the exposed leaves declined significantly more in the upper canopy of P. tremula, which is not consistent with the suggestion that the leaves with the highest VAZ content are more resistant to photoinhibition. This study demonstrates that previous leaf light environment may significantly affect the adaptation capacity of foliage to altered light environment, and also that species differences in photosynthetic capacity and acclimation potentials importantly alter this interaction.     

Dehydration-mediated activation of the xanthophyll cycle in darkness: is it related to desiccation tolerance?

The development of desiccation tolerance by vegetative tissues was an important step in the plants’ conquest of land. To counteract the oxidative stress generated under these conditions the xanthophyll cycle plays a key role. Recent reports have shown that desiccation itself induces de-epoxidation of xanthophyll cycle pigments, even in darkness. The aim of the present work was to study whether this trait is a common response of all desiccation-tolerant plants. The xanthophyll cycle activity and the maximal photochemical efficiency of PS II (F _v/F _m) as well as β-carotene and α-tocopherol contents were compared during slow and rapid desiccation and subsequent rehydration in six species pairs (with one desiccation-sensitive and one desiccation-tolerant species each) belonging to different taxa. Xanthophyll cycle pigments were de-epoxidised in darkness concomitantly with a decrease in F _v/F _m during slow dehydration in all the desiccation-tolerant species and in most of the desiccation-sensitive ones. De-epoxidation was reverted in darkness by re-watering in parallel with the recovery of the initial F _v/F _m. The stability of the β-carotene pool confirmed that its hydroxylation did not contribute to zeaxanthin formation. The α-tocopherol content of most of the species did not change during dehydration. Because it is a common mechanism present in all the desiccation-tolerant taxa and in some desiccation-sensitive species, and considering its role in antioxidant processes and in excess energy dissipation, the induction of the de-epoxidation of xanthophyll cycle pigments upon dehydration in the dark could be understood as a desiccation tolerance-related response maintained from the ancestral clades in the initial steps of land occupation by plants.     

Elevated ΔpH restores rapidly reversible photoprotective energy dissipation in <Emphasis Type="Italic">Arabidopsis</Emphasis> chloroplasts deficient in lutein and xanthophyll cycle activity

The xanthophylls of the light-harvesting complexes of photosystem II (LHCII), zeaxanthin, and lutein are thought to be essential for non-photochemical quenching (NPQ). NPQ is a process of photoprotective energy dissipation in photosystem II (PSII). The major rapidly reversible component of NPQ, qE, is activated by the transmembrane proton gradient, and involves the quenching of antenna chlorophyll excited states by the xanthophylls lutein and zeaxanthin. Using diaminodurene (DAD), a mediator of cyclic electron flow around photosystem I, to enhance ΔpH we demonstrate that qE can still be formed in the absence of lutein and light-induced formation of zeaxanthin in chloroplasts derived from the normally qE-deficient lut2npq1 mutant of Arabidopsis. The qE induced by high ΔpH in lut2npq1 chloroplasts quenched the level of fluorescence when all PSII reaction centers were in the open state (F _o state), protected PSII reaction centers from photoinhibition, was sensitive to the uncoupler nigericin, and was accompanied by absorption changes in the 410–565 nm region. Titrations show the ΔpH threshold for activation of qE in lut2npq1 chloroplasts lies outside the normal physiological range and is highly cooperative. Comparison of quenching in isolated trimeric (LHCII) and monomeric (CP26) light-harvesting complexes from lut2npq1 plants revealed a similarly shifted pH dependency compared with wild-type LHCII. The implications for the roles of lutein and zeaxanthin as direct quenchers of excitation energy are discussed. Furthermore, we argue that the control over the proton-antenna association constant, pK, occurs via influence of xanthophyll structure on the interconnected phenomena of light-harvesting antenna reorganization/aggregation and hydrophobicity.     

Analysis of ΔpH and the xanthophyll cycle in NPQ of the Antarctic sea ice alga Chlamydomonas sp. ICE-L

Non-photochemical fluorescence quenching (NPQ) is mainly associated with the transthylakoid proton gradient (ΔpH) and xanthophyll cycle. However, the exact mechanism of NPQ is different in different oxygenic photosynthetic organisms. In this study, several inhibitors were used to study NPQ kinetics in the sea ice alga Chlamydomonas sp. ICE-L and to determine the functions of ΔpH and the xanthophyll cycle in the NPQ process. NH₄Cl and nigericin, uncouplers of ΔpH, inhibited NPQ completely and zeaxanthin (Z) was not detected in 1 mM NH₄Cl-treated samples. Moreover, Z and NPQ were increased in the samples containing N,N’-dicyclohexyl-carbodiimide (DCCD) under low light conditions. We conclude that ΔpH plays a major role in NPQ, and activation of the xanthophyll cycle is related to ΔpH. In dithiothreitol (DTT)-treated samples, no Z was observed and NPQ decreased. NPQ was completely inhibited when NH₄Cl was added suggesting that part of the NPQ process is related to the xanthophyll cycle and the remainder depends on ΔpH. Moreover, lutein and β-carotene were also essential for NPQ. These results indicate that NPQ in the sea ice alga Chlamydomonas sp. ICE-L is mainly dependent on ΔpH which affects the protonation of PSII proteins and de-epoxidation of the xanthophyll cycle, and the transthylakoid proton gradient alone can induce NPQ.     

Can energy policies affect the cycle of carbon emissions? Case study on the energy consumption of industrial terminals in Shanghai,Jiangsu and Zhejiang

This paper proposes an approach to calculate the time series of cumulative carbon dioxide (CO₂) emissions between 1995 and 2014 based on industrial energy consumption data in three Eastern China jurisdictions in Shanghai, Jiangsu and Zhejiang during these two decades. Using the Hodrick-Prescott filter, the fluctuation components of the cumulative CO₂-emission time-series data in the three provinces are obtained. Subsequently, a grey correlation-based change-point search algorithm is used to determine change-points in these data. Additionally, the CO₂-emission time-series is divided into stages based on the change-points. The cycle characteristics of national energy policies, laws, and regulations are compared with those of the cumulative CO₂-emission cycle of the three provinces to analyse the impact of energy policies on CO₂ emissions. This study shows that, although the industrial structure and trends in the CO₂ emission time-series data of the three provinces are different, their cumulative CO₂-emission cycle remains the same from 1995 to 2014. The variation characteristics of the cumulative CO₂ emissions for each cycle during this period are well aligned with the stage characteristics of energy policies, laws, and regulations, indicating that energy policies play a consistent role in regulating such emissions. This study examines low-carbon production and sustainable energy development, and offers suggestions for issuing and perfecting energy policies, laws, and regulations, considering the indicators of energy consumption and CO₂ emissions.     

Phosphatidylcholine and the CDP–choline cycle

The CDP–choline pathway of phosphatidylcholine (PtdCho) biosynthesis was first described more than 50 years ago. Investigation of the CDP–choline pathway in yeast provides a basis for understanding the CDP–choline pathway in mammals. PtdCho is considered as an intermediate in a cycle of synthesis and degradation, and the activity of a CDP–choline cycle is linked to subcellular membrane lipid movement. The components of the mammalian CDP–choline pathway include choline transport, choline kinase, phosphocholine cytidylyltransferase, and choline phosphotransferase activities. The protein isoforms and biochemical mechanisms of regulation of the pathway enzymes are related to their cell‐ and tissue-specific functions. Regulated PtdCho turnover mediated by phospholipases or neuropathy target esterase participates in the mammalian CDP–choline cycle. Knockout mouse models define the biological functions of the CDP–choline cycle in mammalian cells and tissues. This article is part of a Special Issue entitled Phospholipids and Phospholipid Metabolism.     

Oligosaccharins and Pectimorf? stimulate root elongation and shorten the cell cycle in higher plants

The aim was to test promotive effects of oligosaccharins on root growth and development at the root apical meristem and the cell cycle using the model systems, Arabidopsis thaliana and the tobacco (Nicotiana tabacum) BY-2 cell line. Arabidopsis was grown on medium supplemented with 0.1?mg L^?1 oligoxyloglucan (OX), 10?mg L^?1 Pectimorf^? (P) or 0.5?mg L^?1 indole butyric acid (IBA). Primary root length, number of lateral root primordia, root apical meristem (RAM) length and epidermal cell length were recorded. Three genotypes were used: wild type (WT) and transgenic lines expressing either Schizosaccharomyces pombe (Sp) cdc25 or over-expressing^(oe) Arath;WEE1. All treatments promoted primary root elongation but repressed lateral root production. Only P had a clear positive effect on meristem length whereas all other genotype?×?treatment interactions showed shorter RAMs. Whilst IBA, OX and P induced an increase in cell length in Spcdc25, the same treatments caused a significant decrease in WEE1 ^oe . Mitotic indices were also significantly higher in roots treated with oligosaccharins suggesting a shortening of the cell cycle. This hypothesis was tested in the BY-2 cell line. Both OX and P shortened the cell cycle exclusively through a shortening of G1 whilst mitotic cell size remained constant between treatments. In conclusion, both OX and P do indeed stimulate growth and shorten the cell cycle in higher plants and at the cellular level are able to reverse large and small cell size phenotypes normally exhibited by WEE1 ^oe and Spcdc25 genotypes, respectively.     

How much energy does the breast fed infant consume and expend?

Energy intake in breast fed infants is uncertain. The doubly labelled water method was used to measure, simultaneously and non-invasively, energy expenditure, energy intake, milk volume intake, energy deposition, and the energy content of breast milk in 12 "free living" breast fed babies at 5 and 11 weeks of age. The validity of this new approach was assessed in a parallel study in 12 formula fed infants. The babies who were exclusively breast fed expended 1.28 and 1.68 MJ/day at five and 11 weeks and had intakes of 1.81 and 2.22 MJ/day; these intakes were associated with normal growth but were well below those recommended previously. At five and 11 weeks the calculated energy content of breast milk was 0.24 and 0.25 MJ/100 ml, which is substantially lower than that commonly reported in milk obtained unphysiologically by expression of the breast. These data cast doubt on the widely used published standards for infant feeding.     

Phenolic compounds in black currant leaves – an interaction between the plant and foliar diseases?

Interactions between phenolic compounds in black currant leaves and foliar diseases may be important in breeding for resistant genotypes with a nutritional high profile for human applications. For increased understanding of such interactions, we evaluated the presence of major fungal diseases by visual inspection, and content of phenolic compounds by HPLC in leaves of five segregating black currant breeding populations. Eight individual flavonols (e.g. quercetin-3-O-glucoside, quercetin-3-O-rutinoside and kaempferol-malonylgucoside), three flavan-3-ols (epigallocatechin, catechin and epicatechin) and two chlorogenic acids (neochlorogenic acid and chlorogenic acid) were significantly correlated to the leaf diseases. Rib-0701 was the population possessing the highest content for several of the compounds, while genotype differences existed for content of various phenolic compounds and resistance to the diseases. The high variability of content of phenolic compounds opens up for opportunities to breed resistant genotypes with improved health properties of the leaves for functional food products.     

Increasing the lifetime of products by nanomaterial inclusions—life cycle energy implications

The International Journal of Life Cycle Assessment - Typically, the high energy required to manufacture nanomaterials is weighed against the benefits transferred to a product. Adequately...     

Do lipids shape the eukaryotic cell cycle?

Successful passage through the cell cycle presents a number of structural challenges to the cell. Inceptive studies carried out in the last five years have produced clear evidence of modulations in the lipid profile (sometimes referred to as the lipidome) of eukaryotes as a function of the cell cycle. This mounting body of evidence indicates that lipids play key roles in the structural transformations seen across the cycle. The accumulation of this evidence coincides with a revolution in our understanding of how lipid composition regulates a plethora of biological processes ranging from protein activity through to cellular signalling and membrane compartmentalisation. In this review, we discuss evidence from biological, chemical and physical studies of the lipid fraction across the cell cycle that demonstrate that lipids are well-developed cellular components at the heart of the biological machinery responsible for managing progress through the cell cycle. Furthermore, we discuss the mechanisms by which this careful control is exercised.     

Cell cycle: who turns the crank?

The oscillating activity of a single CDK-cyclin fusion protein can drive the orderly progression of yeast cells through DNA replication, mitosis and cell division.     

Do nuclear and renewable energy improve the environment? Empirical evidence from the United States

The central focus of this article is to assess the dynamic effects of nuclear and renewable energy consumption on CO₂ emissions, for a given level of income and energy consumption. We apply an autoregressive distributed lag (ARDL) approach to cointegration to U.S. data from 1960 to 2010. We find that nuclear energy consumption indeed reduces CO₂ emissions in both the short- and long-run, while renewable energy consumption does only in the short-run. We also find that income increases CO₂ emissions in the long-run after showing the environmental Kuznets curve (EKC) initially in the short-run. Finally, energy consumption is found to have a negative impact on reducing CO₂ emissions in the short- and long-run.     

When does a functional correctly describe both the structure and the energy of the transition state?

Requiring that several properties are well reproduced is a severe test on density functional approximations. This can be assessed through the estimation of joint and conditional success probabilities. An example is provided for a small set of molecules, for properties characterizing the transition states (geometries and energies).