Are there associations between grain-filling rate and photosynthesis in the flag leaves of field-grown rice?

Rate of grain filling in terms of dry mass accumulated per panicle per day was measured in field-grown rice in the dry season in the Philippines and compared to rates of light-saturated photosynthesis per unit leaf area (P(max)) measured at 350 micro l l(-1) CO(2) for 21 d after flowering. Five new plant type (tropical japonica) varieties (NPT) and one indica variety (IR72) were used and these gave some variation in rates and patterns of grain filling. A rapid grain-filling phase (RGFP) occurred approximately 10 d after flowering in most varieties. There was no consistent relationship in any variety between the rate of grain-filling and P(max) and chlorophyll content, both of which remained mostly unchanged throughout grain filling. Significant declines in the amount of total leaf protein and ribulose bisphosphate carboxylase-oxygenase (Rubisco) occurred, but these did not occur at the same time as the RGFP in all varieties. A decrease in the ratio of chlorophyll a/b preceded these changes and a transient rise in chlorophyll content was also observed in four varieties at this time. There was no significant change in leaf non-structural carbohydrate content during or following the RGFP. It is concluded that the decline in Rubisco and protein content in NPT was not reflected in photosynthetic activity. Hence in these field experiments Rubisco accumulated to a level in excess of photosynthetic requirements, serving as a store of nitrogen for grain filling.     

Body temperature and sleep: Are they controlled by the same mechanism?

Simultaneous changes in sleep and body temperature, produced either by lesion or by stimulation of the medial preoptic area (mPOA), have given reasons to suggest that thermoregulation and sleep regulation are controlled by the same set of neurons. The reasons for simultaneous changes in these parameters are discussed in the present paper with a view to explaining the relationship between thermoregulation and sleep regulation. Changes in body temperature and sleep on destruction of the preoptic area (POA) neurons and the sequence of these changes, suggest a separate control mechanism in the mPOA for regulation of sleep and body temperature. Evidence is put forward in the present paper to show that the mPOA is not involved in the downregulation or upregulation of changes in body temperature with alteration in the vigilance state. On the other hand, circadian modulation of body temperature is possibly involved in altering sleep propensity. A clear indication regarding separate control of sleep and body temperature came from the studies in which noradrenergic agents were applied into the mPOA of animals with and without lesion of the noradrenergic fibers projecting to the mPOA. Experiments in which sleep was analyzed after experimental manipulations of ambient temperature and body temperature, including peripheral, core and brain temperature, are presented here to show a close relationship between thermoregulation and sleep regulation. Various theories regarding the regulation of body temperature during slow wave sleep and rapid eye movement sleep are also discussed. The functional integrity of the mPOA may be essential not only for the regulation of body temperature and sleep-wakefulness but even for the homeostatic regulation of energy balance of the body in response to alterations in environmental temperature and sleep-wakefulness.

     

Are all GMOs the same? Consumer acceptance of cisgenic rice in India

India has more than 215 million food‐insecure people, many of whom are farmers. Genetically modified (GM) crops have the potential to alleviate this problem by increasing food supplies and strengthening farmer livelihoods. For this to occur, two factors are critical: (i) a change in the regulatory status of GM crops, and (ii) consumer acceptance of GM foods. There are generally two classifications of GM crops based on how they are bred: cisgenically bred, containing only DNA sequences from sexually compatible organisms; and transgenically bred, including DNA sequences from sexually incompatible organisms. Consumers may view cisgenic foods as more natural than those produced via transgenesis, thus influencing consumer acceptance. This premise was the catalyst for our study—would Indian consumers accept cisgenically bred rice and if so, how would they value cisgenics compared to conventionally bred rice, GM‐labelled rice and ‘no fungicide’ rice? In this willingness‐to‐pay study, respondents did not view cisgenic and GM rice differently. However, participants were willing‐to‐pay a premium for any aforementioned rice with a ‘no fungicide’ attribute, which cisgenics and GM could provide. Although not significantly different (P = 0.16), 76% and 73% of respondents stated a willingness‐to‐consume GM and cisgenic foods, respectively.     

Is light quality involved in the regulation of the photosynthetic apparatus in attached rice leaves?

The regulatory effect of light quality on the photosynthetic apparatus in attached leaves of rice plants was investigated by keeping rice plants under natural light, in complete darkness, or under illumination with light of different colors. When leaves were left in darkness and far-red (FR)-light conditions for 6 days at 30°C, there was an initial lag in chlorophyll (Chl) content, Chl a/b ratio, and maximum photosystem (PS) II photochemistry that lasted until the second day; these then rapidly decreased on the fourth day. In contrast, ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) rapidly disappeared with no lag under low or zero light conditions. By using spectrophotometric quantitation, it was determined that the PSII and PSI reaction centers were regulated by light quality, but cytochrome (Cyt) f was regulated by light intensity. However, the PSII heterogeneity was also strongly modified by the light intensity; PSIIα with the large antenna decreased markedly both in content and in antenna size. Consequently, the PSIIα/PSI ratio declined under FR-light because the low intensity of FR-light dominated over its quality in the modulation of the PSIIα/PSI ratio. An imbalance between them induced the generation of reactive oxygen species (ROS), although the ROS were scavenged by stromal enzymes such as superoxide dismutase (SOD), ascorbate peroxidase (APX), and glutathione reductase (GR). The activities of these stromal enzymes are also regulated by light quality. Thus, although the photosynthetic apparatus is regulated differently depending on light quality, light quality may play an important role in the regulation of the photosynthetic apparatus.     

What's in a name? Are MSG and umami the same?

The Japanese word `umami' has a long past. It was already inuse during the Edo period (Tokugawa Shogunate) of Japanese history,which ended in 1868 (Mason, 1993). In Japanese, `umami' oftenconnotes a cognitive category (Yamaguchi and Ninomiya, 1998) oftaste, or perhaps flavor, with definitions that include deliciousness, flavor,relish,     

Are monophyly and synapomorphy the same or different? Revisiting the role of morphology in phylogenetics

Species are groups of organisms, marked out by reproductive (replicative) properties. Monophyletic taxa are groups of species, marked out by synapomorphies. In Nelson’s analysis, monophyly and synapomorphy are identical relations. Monophyly and synapomorphy, however, are not equivalent relations. Monophyly is epistemically not accessible, whereas synapomorphy is epistemically accessible through character analysis. Monophyly originates with speciation, the two sister‐species that come into being through the splitting of the ancestral species lineage forming a monophyletic taxon at the lowest level of inclusiveness. Synapomorphy provides the empirical evidence for monophyly, inferred from character analysis in the context of a three‐taxon statement. If synapomorphy and monophyly were equivalent, phylogenetic systematists should find a single tree, instead of multiple equally parsimonious trees. Understanding synapomorphy as the relevant evidence for phylogenetic inference reveals a category mistake in contemporary phylogenetics: the treatment of morphological characters mapped onto molecular trees as synapomorphies and homoplasies. The mapping of morphological characters onto nodes of a molecular tree results in an empirically empty procedure for synapomorphy discovery. Morphological synapomorphies and homoplasies can only be discovered by morphological and combined analyses. The use of morphology in phylogenetic inference in general is defended by examples from Laurales and Squamata in particular. To make empirical evidence scientifically relevant in order to search for concordance, or dis‐concordance, of phylogenetic signal, is certainly more fruitful for phylogenetics than the uncritical mapping of morphological traits on a molecular scaffold. © The Willi Hennig Society 2010.     

Are NPY and enkephalins costored in the same noradrenergic neurons and vesicles?

Separate studies show that NPY and enkephalins are widely distributed in peripheral noradrenergic neurons. In the present study, the subcellular costorage and release in response to intense sympathetic stimulation and reserpine at near therapeutic doses (0.05 mg/kg every other day) were examined. In young pig arteries and vas deferens, enkephalin and D beta H immunofluorescence show consistent but not total overlap. Also NPY is colocalized with D beta H in many fibers but with VIP (nonnoradrenergic) in others. Ultrastructural immunogold labeling indicates that individual terminals contain large dense cored vesicles (LDVs) which store either NPY or enkephalins, even though costorage of both peptides occurs. Some LDVs costore NPY and VIP, especially in the middle cerebral artery and in the lamina propria of vas deferens. Acute CNS ischemia depletes enkephalins and norepinephrine in all tissues analyzed without parallel loss of NPY. Reserpine depletes norepinephrine 70-85% but does not deplete NPY or enkephalins. The latter is in contrast to commonly used high doses known to produce nonspecific, detergent-like effects. In fact, low doses of reserpine induce a time-dependent new synthesis and processing of NPY precursor peptides in vas deferns. Contrasting effects of reserpine on NPY and enkephalin contents, new synthesis and apparent processing, and a differential response to acute CNS ischemia were found in every tissue studied. Activation of precursor neuropeptide processing occurred immediately upon intense sympathetic stimulation in most tissues. Dual localization of NPY in noradrenergic and nonnoradrenergic fibers and differences in subcellular LDV storage help explain why enkephalin correlates better than NPY with norepinephrine loss in response to acute CNS ischemia. Furthermore, the costorage of NPY and enkephalins in distinct subpopulations of noradrenergic fibers, which varies according to tissue, is likely to be under separate CNS control.     

Senescence in wheat leaves: is a cysteine endopeptidase involved in the degradation of the large subunit of Rubisco?

In wheat (Triticum aestivum L.), leaf senescence can be initiated by different factors. Depending on the plant system (intact plants or detached leaves) or the environmental conditions (light, nutrient availability), the symptoms of senescence differ. The aim of this work was to elucidate the catabolism of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco, EC. 4.1.1.39) under various senescence-inducing conditions. Leaf senescence was initiated in intact plants by darkness or by N-deprivation and in leaf segments by exposure to light or darkness. Depending on the treatment, a 50 kDa fragment of Rubisco was observed. The formation of this fragment was enhanced by leaf detachment and low light. In segments exposed to high light and in intact plants induced to senesce by N-deprivation, the fragment was essentially absent. Since an antibody against the N-terminus of a large subunit of Rubisco (LSU) did not cross-react with the fragment, it appears likely that a smaller fragment was removed from the N-terminus of LSU. Inhibitor studies suggest that a cysteine endopeptidase was involved in the formation of the 50 kDa fragment. Non-denaturing-PAGE followed by SDS-PAGE revealed that the fragment was produced while LSU was integrated in the holoenzyme complex, and that it remained there after being produced. It remains open how the putative endopeptidase reaches the stromal protein Rubisco. The results indicate that depending on the senescence-inducing conditions, different proteolytic enzymes may be involved. The involvement of vacuolar proteases must be considered as occurring during LSU degradation, which takes place in darkness, low light or under carbon limitation.     

Are fear memories made and maintained by the same NMDA receptor-dependent mechanisms?

A recent finding indicates that inducible knockout of the NR1 NMDA receptor subunit promotes the loss of fear memories formed months earlier. One view is that posttraining NMDA receptor activation protects modified synapses from "synaptic drift." An alternative view is that NMDA receptors help maintain appropriate connectivity in memory-encoding networks.     

Are tyrosine residues involved in the photoconversion of the water‐soluble chlorophyll‐binding protein of Chenopodium album?

Non‐photosynthetic and hydrophilic chlorophyll (Chl) proteins, called water‐soluble Chl‐binding proteins (WSCPs), are distributed in various species of Chenopodiaceae, Amaranthaceae, Polygonaceae and Brassicaceae. Based on their photoconvertibility, WSCPs are categorised into two classes: Class I (photoconvertible) and Class II (non‐photoconvertible). Chenopodium album WSCP (CaWSCP; Class I) is able to convert the chlorin skeleton of Chl a into a bacteriochlorin‐like skeleton under light in the presence of molecular oxygen. Potassium iodide (KI) is a strong inhibitor of the photoconversion. Because KI attacks tyrosine residues in proteins, tyrosine residues in CaWSCP are considered to be important amino acid residues for the photoconversion. Recently, we identified the gene encoding CaWSCP and found that the mature region of CaWSCP contained four tyrosine residues: Tyr13, Tyr14, Tyr87 and Tyr134. To gain insight into the effect of the tyrosine residues on the photoconversion, we constructed 15 mutant proteins (Y13A, Y14A, Y87A, Y134A, Y13‐14A, Y13‐87A, Y13‐134A, Y14‐87A, Y14‐134A, Y87‐134A, Y13‐14‐87A, Y13‐14‐134A, Y13‐87‐134A, Y14‐87‐134A and Y13‐14‐87‐134A) using site‐directed mutagenesis. Amazingly, all the mutant proteins retained not only chlorophyll‐binding activity, but also photoconvertibility. Furthermore, we found that KI strongly inhibited the photoconversion of Y13‐14‐87‐134A. These findings indicated that the four tyrosine residues are not essential for the photoconversion.     

Relationships between optically assessed polyphenols and chlorophyll contents,and leaf mass per area ratio in woody plants: a signature of the carbon–nitrogen balance within leaves?

Chlorophyll (Chl) and epidermal polyphenol (EPhen) contents were estimated in vivo using two optical leaf-clips, SPAD-502 and Dualex, respectively. The area-based measurements were transformed into mass-based data by taking into account the leaf dry mass per area (LMA). Measurements were performed on forest trees and on saplings grown under controlled conditions. While LMA increased with irradiance along a vertical transect in a beech canopy or in saplings grown under different and increasing irradiance levels, mass-based EPhen (EPhen(m)) increased, whereas mass-based Chl (Chl(m)) decreased. This was a signature of a gradual switch of investment from protein into polyphenol production. A similar signature was obtained in saplings grown on nitrogen-deficient soil with respect to fertilized controls. However, nitrogen effects remained moderate compared to irradiance-induced effects. EPhen(m) and Chl(m) both declined with plant ageing-induced increases in LMA, under all tested growth conditions. This was a signature of an accumulation of dry matter that diluted Chl and EPhen. The described competition between Chl and EPhen in leaves fits well with the predictions of the Protein Competition Model (PCM), that is, that the total leaf mass-based polyphenols content (Phen(t)) is controlled by the competition between protein and polyphenol biosynthetic pathways and its metabolic regulation.     

Effect of codon optimization on the enhancement of the β-carotene contents in rice endosperm

A β-carotene is the most well-known dietary source as provitamin A carotenoids. Among β-carotene-producing Golden Rice varieties, PAC (Psy:2A:CrtI) rice has been previously developed using a bicistronic recombinant gene that linked the Capsicum Psy and Pantoea CrtI genes by a viral 2A sequence. To enhance β-carotene content by improving this PAC gene, its codon was optimized for rice plants (Oryza sativa L.) by minimizing the codon bias between the transgene donor and the host rice and was then artificially synthesized as stPAC (stPsy:2A:stCrtI) gene. The GC content (58.7 from 50.9%) and codon adaptation index (0.85 from 0.77) of the stPAC gene were increased relative to the original PAC gene with 76% DNA identity. Among 67 T₁ seeds of stPAC transformants showing positive correlations between transgene copy numbers (up to three) and carotenoid contents, three stPAC lines with a single intact copy were chosen to minimize unintended insertional effects and compared to the representative line of the PAC transgene with respect to their codon optimization effects. Translation levels were stably increased in all three stPAC lines (3.0-, 2.5-, 2.9-fold). Moreover, a greater intensity of the yellow color of stPAC seeds was correlated with enhanced levels of β-carotene (4-fold, 2.37 μg/g) as well as total carotenoid (2.9-fold, 3.50 μg/g) relative to PAC seeds, suggesting a β-branch preference for the stPAC gene. As a result, the codon optimization of the transgene might be an effective tool in genetic engineering for crop improvement as proven at the enhanced levels of translation and carotenoid production.     

Are NADP-dependent isocitrate dehydrogenases and ferredoxin-dependent glutamate synthase co-regulated by the same photoreceptors?

Activities of NADP-dependent isocitrate dehydrogenases (cytosolic and plastidic isoforms, ICDH1 and ICDH2; EC 1.1.1.42) and ferredoxin-dependent glutamate synthase (Fd-GOGAT; EC 1.4.7.1) in turions of Spirodela polyrhiza were all stimulated by light. Single or repeated red light (R) pulses induced the activity of the enzymes and this effect was reverted by subsequent far-red light (FR) pulses. The enzymes are, therefore, co-regulated by the low-fluence response of phytochrome. For ICDH, this is reported here for the first time. Neither an effect of the very low-fluence response nor of the FR-mediated high-irradiance response was detectable. Irradiance with continuous R resulted in enhanced enzyme activities and protein levels (Western analysis using polyclonal antibodies against ICDH1 and Fd-GOGAT). These additional effects of continuous R (called a non-induction effect) could be inhibited for ICDH1 and ICDH2 by the inhibitor of photosynthetic electron transport, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, and are therefore related to the effect of photosynthesis. In contrast, the non-induction effect of Fd-GOGAT was resistant against this inhibitor. Moreover, hourly R pulses did not replace the effect of continuous R. The non-induction effect of light on the activity and protein level of Fd-GOGAT was therefore tentatively classified as an R-mediated high-irradiance response. The activity of Fd-GOGAT but not that of ICDHs was additionally regulated by a specific blue-light receptor. It can be concluded that the levels of ICDHs and Fd-GOGAT were coordinated by light but were not co-regulated by the same photoreceptors. Nitrate is necessary for the light regulation of both enzymes, contributing to the coordinated expression of the relevant genes.Abbreviations DCMU 3-(3,4-Dichlorophenyl)-1,1-dimethylurea - Fd-GOGAT Ferredoxin-dependent glutamate synthase - FR Far-red light - HIR High-irradiance response - ICDH NADP-dependent isocitrate dehydrogenase - ICDH1 Cytosolic ICDH - ICDH2 Chloroplastic ICDH - LFR Low-fluence response - R Red light - SDS–PAGE Denaturing polyacrylamide gel electrophoresis - VLFR Very low-fluence response     

Are protein complexes made of cores,modules and attachments?

It has recently been proposed by Gavin et al. (Nature 2006, 440, 631-636) that protein complexes in the cell exist in different forms. The proteins within each complex were proposed to exist as three different classes, being core, module or attachment proteins. This study investigates whether the core-module-attachment classification of proteins within each complex is supported by other high-throughput protein data. Core proteins were found to have lower abundance, and shorter half-life as compared to attachment proteins, whilst the abundance and half-life of core and module proteins were similar. When the cell was perturbed, core proteins had smaller changes in abundance as compared to module and attachment proteins. Comparisons between six different pairwise interaction types of core, module and attachment proteins within a complex showed interaction types involving core or module proteins were more likely to be mediated by domain-domain interactions (DDIs) than interaction types involving attachment proteins. Interaction types that involve attachment proteins had a relatively higher ratio of abundance and ratio of half-life. So we conclude that, the core, module and attachment model of protein complexes is supported by data from these proteomic scale datasets, and describe a model for a typical protein complex that considers the above results.     

Expression profile of the α subunit of the heterotrimeric G protein in rice

Previous studies on the activity of the rice Gα promoter using a β-Glucuronidase (GUS) reporter construct indicated that Gα expression was highest in developing organs and changed in a developmental stage-dependent manner. In this paper, GUS activity derived from the rice Gα promoter was analyzed in seeds and developing leaves. In seeds, GUS activity was detected in the aleurone layer, embryo, endosperm and scutellar epithelium. In developing leaves, the activity was detected in the mesophyll tissues, phloem and xylem of the leaf sheath and in the mesophyll tissue of the leaf blade. The activity in the aleurone layer and scutellar epithelium suggests that the Gα subunit may be involved in gibberellin signaling. The activity in the mesophyll tissues of the leaf blade suggests that the Gα subunit may be related to the intensity of disease resistance. The pattern of the activity in the developing leaf also indicates that the expression of Gα follows a developmental profile at the tissue level.Key words: expression pattern, Gα subunit, GUS staining pattern, heterotrimeric G protein, riceThe rice mutant d1 is deficient in the heterotrimeric G protein α subunit (Gα). Recently it was found that the dwarfism phenotype of d1 is due to a reduction in cell numbers.¹ This discovery has led to new questions regarding how rice Gα regulates cell number, and which other signaling molecules are involved in this process in various tissues and at different development stages. Studies of d1 suggest that rice Gα participates in both gibberellin signaling^2–4 and brassinosteroid signaling.^5–8 Promoter studies using the β-Glucuronidase (GUS) reporter indicate that Gα expression is highest in developing organs.¹ In this paper, we report on the expression pattern of a Gα promoter::GUS construct in seeds and developing leaves of rice.