Changes in rubisco content in relation to saccharides accumulation in wheat leaves during day

Two wheat varieties, T. durum (HD 4502) and T. aestivum (Kalyansona) were examined for photosynthesis rate and contents of sugars and rubisco protein in the flag leaf, at forenoon and afternoon at anthesis stage. A decrease in photosynthesis rate was observed in the afternoon compared to forenoon in both the varieties and was associated with an increase in non-reducing sugars and a decrease in rubisco content in the leaves.     

Enterohaemorrhagic and enteropathogenic Escherichia coli Tir proteins trigger a common Nck-independent actin assembly pathway

The Tir proteins of enterohaemorrhagic and enteropathogenic Escherichia coli (EHEC and EPEC respectively) are each translocated into the host plasma membrane where they promote F-actin pedestals in epithelial cells beneath adherent bacteria, but the two proteins act by different means. The canonical EPEC Tir becomes phosphorylated on tyrosine residue 474 (Y474) to recruit the host adaptor protein Nck, and also stimulates an inefficient, Nck-independent pathway utilizing tyrosine residue 454 (Y454). In contrast, the canonical EHEC Tir lacks Y474 and instead utilizes residues 452-463 to recruit EspF(U), an EHEC-specific effector that stimulates robust Nck-independent actin assembly. EHEC Tir Y458 and EPEC Tir Y454 are both part of an asparagine-proline-tyrosine (NPY) sequence. We report that each of the EHEC Tir NPY residues is required for EspF(U) recruitment and pedestal formation, and each of the EPEC Tir NPY residues is critical for inefficient, Nck-independent pedestal formation. Introduction of EspF(U) into EPEC dramatically enhanced Nck-independent actin assembly by EPEC Tir in a manner dependent on NPY(454). These results suggest that EPEC and EHEC Tir trigger a common Nck-independent actin assembly pathway and are both derived from an ancestral Tir molecule that utilized NPY to stimulate low-level pedestal formation.     

Transamination of glutamic acid during germination, growth and seed development in Bengal gram

The activity of glutamic acid aminotransferase with respect to six keto acids was studied in dialysed extracts obtained from germinating seeds, leaves of plants at seedling, preanthesis and postanthesis stages and the developing seeds of Bengal gram. There was a considerable amount of non-enzymic aminotransferase activity which changed at different stages of growth. The efficiency of glutamic acid to transfer amino group to various keto acids also varied in two different varieties in relation to growth and development. The possibility of the existence of either many aminotransferases or of several isozymes is discussed.     

ATM-NFκB axis-driven TIGAR regulates sensitivity of glioma cells to radiomimetics in the presence of TNFα

Gliomas are resistant to radiation therapy, as well as to TNFα induced killing. Radiation-induced TNFα triggers Nuclear factor κB (NFκB)-mediated radioresistance. As inhibition of NFκB activation sensitizes glioma cells to TNFα-induced apoptosis, we investigated whether TNFα modulates the responsiveness of glioma cells to ionizing radiation-mimetic Neocarzinostatin (NCS). TNFα enhanced the ability of NCS to induce glioma cell apoptosis. NCS-mediated death involved caspase-9 activation, reduction of mitochondrial copy number and lactate production. Death was concurrent with NFκB, Akt and Erk activation. Abrogation of Akt and NFκB activation further potentiated the death inducing ability of NCS in TNFα cotreated cells. NCS-induced p53 expression was accompanied by increase in TP53-induced glycolysis and apoptosis regulator (TIGAR) levels and ATM phosphorylation. siRNA-mediated knockdown of TIGAR abrogated NCS-induced apoptosis. While DN-IκB abrogated NCS-induced TIGAR both in the presence and absence of TNFα, TIGAR had no effect on NFκB activation. Transfection with TIGAR mutant (i) decreased apoptosis and γH2AX foci formation (ii) decreased p53 (iii) elevated ROS and (iv) increased Akt/Erk activation in cells cotreated with NCS and TNFα. Heightened TIGAR expression was observed in GBM tumors. While NCS induced ATM phosphorylation in a NFκB independent manner, ATM inhibition abrogated TIGAR and NFκB activation. Metabolic gene profiling indicated that TNFα affects NCS-mediated regulation of several genes associated with glycolysis. The existence of ATM-NFκB axis that regulate metabolic modeler TIGAR to overcome prosurvival response in NCS and TNFα cotreated cells, suggests mechanisms through which inflammation could affect resistance and adaptation to radiomimetics despite concurrent induction of death.     

Nucleoside diphosphate kinase of Mycobacterium tuberculosis acts as GTPase-activating protein for Rho-GTPases

Several bacterial pathogens secrete proteins into the host cells that act as GTPase-activating proteins (GAPs) for Rho-GTPases and convert GTP-bound active form to GDP-bound inactive form. However, no such effector molecule has been identified in Mycobacterium tuberculosis. In this study, we show that culture supernatant of M. tuberculosis H(37)Rv harbors a protein that stimulates the conversion of GTP-bound Rho-GTPases to the GDP-bound form. Nucleoside diphosphate kinase (Ndk) was identified as this culture supernatant protein that stimulated in vitro GTP hydrolysis by members of Rho-GTPases. The histidine-117 mutant of Ndk, which is impaired for autophosphorylation and nucleotide-binding activities, shows GAP activity. These results suggest that Ndk of M. tuberculosis functions as a Rho-GAP to downregulate Rho-GTPases, and this activity may aid in pathogenesis of the bacteria.     

Variation in carbon stocks on different slope aspects in seven major forest types of temperate region of Garhwal Himalaya,India

The present study was undertaken in seven major forest types of temperate zone (1500 m a.s.l. to 3100 m a.s.l.) of Garhwal Himalaya to understand the effect of slope aspects on carbon (C) density and make recommendations for forest management based on priorities for C conservation/sequestration. We assessed soil organic carbon (SOC) density, tree density, biomass and soil organic carbon (SOC) on four aspects, viz. north-east (NE), north-west (NW), south-east (SE) and south-west (SW), in forest stands dominated by Abies pindrow, Cedrus deodara, Pinus roxburghii, Cupressus torulosa, Quercus floribunda, Quercus semecarpifolia and Quercus leucotrichophora. TCD ranged between 77.3 CMg ha⁻¹ on SE aspect (Quercus leucotrichophora forest) and 291.6 CMg ha⁻¹ on NE aspect (moist Cedrus deodara forest). SOC varied between 40.3 CMg ha⁻¹ on SW aspect (Himalayan Pinus roxburghii forest) and 177.5 CMg ha⁻¹ on NE aspect (moist Cedrus deodara forest). Total C density (SOC + TCD) ranged between 118.1 CMg ha⁻¹ on SW aspect (Himalayan Pinus roxburghii forest) and 469.1 CMg ha⁻¹ on NE aspect (moist Cedrus deodara forest). SOC and TCD were significantly higher on northern aspects as compared with southern aspects. It is recommended that for C sequestration, the plantation silviculture be exercised on northern aspects, and for C conservation purposes, mature forest stands growing on northern aspects be given priority.     

Photosynthetic response of wheat cultivar to long-term exposure to elevated temperature

Wheat (Triticum aestivum L. cv. HD 2285) was grown in control (C) and heated (H) open top chambers (OTCs) for entire period of growth and development till maturity. The mean maximum temperature of the entire period was 3 °C higher in H-compared to C-OTCs. Net photosynthetic rate (P _N) measured at different temperature (20–40 °C) of C-and H-grown plants showed greater sensitivity to high temperature in H-plants. P _N measured at respective growth temperature was lower in H-compared to C-plants. The CO₂ and irradiance response curves of photosynthesis also showed lesser response in H-compared to C-plants. The initial slope of P _N versus internal CO₂ concentration (P _N/C _i) curve was lower in H-than C-plants indicating ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) limitation. In irradiance response curve, the plateau was lower in H-compared to C-plants which is interpreted as RuBPCO limitation. RuBPCO content in the leaves of C-and H-plants, however, was not significantly different. Ribulose-1,5-bisphosphate carboxylase (RuBPC) initial activity was lower in H-plants, whereas activity of fully activated enzyme was not affected, indicating a decrease in activation state of the enzyme. This was further substantiated by the observed decrease in RuBPCO activase activity in H-compared to C-plants. RuBPCO activase was thus sensitive even to moderate heat stress. The decrease in P _N under moderate heat stress was mainly due to a decrease in activation state of RuBPCO catalysed by RuBPCO activase.     

Photosynthetic Acclimation to Elevated CO2 in Relation to Leaf Saccharide Constituents in Wheat and Sunflower

Wheat (T. durum cvs. HD 4502 and B 449, T. aestivum cvs. Kalyansona and Kundan) and sunflower (Helianthus annuus L. cv. Morden) were grown under atmospheric (360±10 cm³ m^–3, AC) and elevated CO₂ (650±50 cm³ m^–3, EC) concentration in open top chambers for entire period of growth and development till maturity. Leaf net photosynthetic rate (P _N) of EC-grown plants of wheat measured at EC was significantly decreased in comparison with AC-plants of wheat measured at EC. Sunflower, however, showed no significant depression in P _N in EC-plants. There was a decrease in ribulose-1,5-bisphosphate carboxylase (RuBPC) activity, its activation state and amount in EC-plants of wheat, whereas no significant decrease was observed in sunflower. The above different acclimation to EC in wheat and sunflower was related with saccharide constituents accumulated in the leaves. Under EC, sunflower accumulated in the leaves more starch, whereas wheat accumulated more sugars.     

Argonaute loading improves the 5' precision of both MicroRNAs and their miRNA* strands in flies

MicroRNAs (miRNAs) are short regulatory RNAs that direct repression of their mRNA targets. The miRNA "seed"-nucleotides 2-7-establishes target specificity by mediating target binding. Accurate processing of the miRNA 5' end is thought to be under strong selective pressure because a shift by just one nucleotide in the 5' end of a miRNA alters its seed sequence, redefining its repertoire of targets (Figure 1). Animal miRNAs are produced by the sequential cleavage of partially double-stranded precursors by the RNase III endonucleases Drosha and Dicer, thereby generating a transitory double-stranded intermediate comprising the miRNA paired to its partially complementary miRNA strand. Here, we report that in flies, the 5' ends of miRNAs and miRNA strands are typically more precisely defined than their 3' ends. Surprisingly, the precision of the 5' ends of both miRNA and miRNA sequences increases after Argonaute2 (Ago2) loading. Our data imply that either many miRNA sequences are under evolutionary pressure to maintain their seed sequences-that is, they have targets-or that secondary constraints, such as the sequence requirements for loading small RNAs into functional Argonaute complexes, narrow the range of miRNA and miRNA 5' ends that accumulate in flies.     

Photosynthetic acclimation to rising atmospheric carbon dioxide concentration

With rising level of CO2 in the atmosphere plants are expected to be exposed to higher concentration of CO2. Since, CO2 is a substrate limiting photosynthesis particularly in C3 plants in the present atmosphere, the impact of elevated CO2 would depend mainly on how photosynthesis acclimates or adjusts to the long term elevated level of CO2. Photosynthetic acclimation is a change in photosynthetic efficiency of leaves due to long term exposure to elevated CO2. This change in photosynthetic efficiency could be a biochemical adjustment that may improve the overall performance of a plant in a high CO2 environment or it could be due to metabolic compulsions as a result of physiological dysfunction. Acclimation has generally become synonymous with the word response, if long term exposure to elevated CO2 decreases the photosynthesis rate (Pn) at a given CO2 level, it is called negative acclimation, if it stimulates Pn at a given CO2 level, it is called positive acclimation. Photosynthetic acclimation is clearly revealed by comparing Pn of ambient and elevated CO2 grown plants at same level of CO2. Species level differences in acclimation to elevated CO2 have been reported. The physiological basis of differential photosynthetic acclimation to elevated CO2 is discussed in relation to the regulation of photosynthesis and photosynthetic carbon partitioning at cellular level.