共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
André Barretto Bruno Wilke Sarah Scaife Luke Alphey Mauro Toledo Marrelli 《Memórias do Instituto Oswaldo Cruz》2013,108(4):529-531
Culex quinquefasciatus mosquitoes have been successfully
genetically modified only once, despite the efforts of several laboratories to
transform and establish a stable strain. We have developed a transient gene
expression method, in Culex, that delivers plasmid DNA directly
to the mosquito haemolymph and additional tissues. We were able to express
DsRed2 fluorescent protein in adult Cx.
quinquefasciatus mosquitoes by injecting plasmids directly into
their thorax. The expression of DsRed2 in adult Cx.
quinquefasciatus mosquitoes is an important stepping stone to
genetic transformation and the potential use of new control strategies and
genetic interactions. 相似文献
3.
Acclimation of Photosynthesis to Elevated CO2
under
Low-Nitrogen Nutrition Is Affected by the Capacity for
Assimilate Utilization. Perennial Ryegrass under
Free-Air
CO2 Enrichment 总被引:3,自引:0,他引:3 下载免费PDF全文
Alistair Rogers Bernt U. Fischer Jonathan Bryant Marco Frehner Herbert Blum Christine A. Raines Stephen P. Long 《Plant physiology》1998,118(2):683-689
Acclimation of photosynthesis to elevated CO2 has previously been shown to be more pronounced when N supply is poor. Is this a direct effect of N or an indirect effect of N by limiting the development of sinks for photoassimilate? This question was tested by growing a perennial ryegrass (Lolium perenne) in the field under elevated (60 Pa) and current (36 Pa) partial pressures of CO2 (pCO2) at low and high levels of N fertilization. Cutting of this herbage crop at 4- to 8-week intervals removed about 80% of the canopy, therefore decreasing the ratio of photosynthetic area to sinks for photoassimilate. Leaf photosynthesis, in vivo carboxylation capacity, carbohydrate, N, ribulose-1,5-bisphosphate carboxylase/oxygenase, sedoheptulose-1,7-bisphosphatase, and chloroplastic fructose-1,6-bisphosphatase levels were determined for mature lamina during two consecutive summers. Just before the cut, when the canopy was relatively large, growth at elevated pCO2 and low N resulted in significant decreases in carboxylation capacity and the amount of ribulose-1,5-bisphosphate carboxylase/oxygenase protein. In high N there were no significant decreases in carboxylation capacity or proteins, but chloroplastic fructose-1,6-bisphosphatase protein levels increased significantly. Elevated pCO2 resulted in a marked and significant increase in leaf carbohydrate content at low N, but had no effect at high N. This acclimation at low N was absent after the harvest, when the canopy size was small. These results suggest that acclimation under low N is caused by limitation of sink development rather than being a direct effect of N supply on photosynthesis. 相似文献
4.
5.
6.
7.
Mutation of Residue Threonine-2 of the D2 Polypeptide and Its
Effect on Photosystem II Function in
Chlamydomonas
reinhardtii 下载免费PDF全文
Christos Andronis Olaf Kruse Zsuzsanna Deák Imre Vass Bruce A. Diner Peter J. Nixon 《Plant physiology》1998,117(2):515-524
The D2 polypeptide of the photosystem II (PSII) complex in the green alga Chlamydomonas reinhardtii is thought to be reversibly phosphorylated. By analogy to higher plants, the phosphorylation site is likely to be at residue threonine-2 (Thr-2). We have investigated the role of D2 phosphorylation by constructing two mutants in which residue Thr-2 has been replaced by either alanine or serine. Both mutants grew photoautotrophically at wild-type rates, and noninvasive biophysical measurements, including the decay of chlorophyll fluorescence, the peak temperature of thermoluminescence bands, and rates of oxygen evolution, indicate little perturbation to electron transfer through the PSII complex. The susceptibility of mutant PSII to photoinactivation as measured by the light-induced loss of PSII activity in whole cells in the presence of the protein-synthesis inhibitors chloramphenicol or lincomycin was similar to that of wild type. These results indicate that phosphorylation at Thr-2 is not required for PSII function or for protection from photoinactivation. In control experiments the phosphorylation of D2 in wild-type C. reinhardtii was examined by 32P labeling in vivo and in vitro. No evidence for the phosphorylation of D2 in the wild type could be obtained. [14C]Acetate-labeling experiments in the presence of an inhibitor of cytoplasmic protein synthesis also failed to identify phosphorylated (D2.1) and nonphosphorylated (D2.2) forms of D2 upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Our results suggest that the existence of D2 phosphorylation in C. reinhardtii is still in question. 相似文献
8.
Imaging of photochemical yield of photosystem II (PSII) computed from leaf chlorophyll fluorescence images and gas-exchange measurements were performed on Rosa rubiginosa leaflets during abscisic acid (ABA) addition. In air ABA induced a decrease of both the net CO2 assimilation (An) and the stomatal water vapor conductance (gs). After ABA treatment, imaging in transient nonphotorespiratory conditions (0.1% O2) revealed a heterogeneous decrease of PSII photochemical yield. This decline was fully reversed by a transient high CO2 concentration (7400 μmol mol−1) in the leaf atmosphere. It was concluded that ABA primarily affected An by decreasing the CO2 supply at ribulose-1,5-bisphosphate carboxylase/oxygenase. Therefore, the An versus intercellular mole fraction (Ci) relationship was assumed not to be affected by ABA, and images of Ci and gs were constructed from images of PSII photochemical yield under nonphotorespiratory conditions. The distribution of gs remained unimodal following ABA treatment. A comparison of calculations of Ci from images and gas exchange in ABA-treated leaves showed that the overestimation of Ci estimated from gas exchange was only partly due to heterogeneity. This overestimation was also attributed to the cuticular transpiration, which largely affects the calculation of the leaf conductance to CO2, when leaf conductance to water is low. 相似文献
9.
10.
11.
12.
13.
Grammatico P Majore S Marrocco G Poscente M Mordenti C Grammatico B Del Porto G 《Genetic counseling (Geneva, Switzerland)》1999,10(4):351-358
We describe a female child with complex cytogenetic anomalies consisting in partial trisomy of the short arm of chromosome 10, terminal deletion of the long arm of chromosome 2 and--at the same time--a mosaicism for X monosomy. To our knowledge, this is the first case reported in which 10p trisomy is associated to a 2qter deletion. Due to the scarcity of cases reported with pure trisomy, it has not been possible to define the 10p+ syndrome precisely yet. Comparison of our proband's phenotype to both the 2q37 deletion and 10p trisomy showed more features described in 2q37- subjects than in 10p+ ones. We also discuss the difficulties of genetic counseling in children with complex aberrations. 相似文献
14.
Cutin Monomers and Surface Wax Constituents Elicit
H2O2 in Conditioned Cucumber Hypocotyl Segments
and Enhance the Activity of Other H2O2
Elicitors 下载免费PDF全文
Markus Fauth Patrick Schweizer Antony Buchala Claus Markst?dter Markus Riederer Tadahiro Kato Heinrich Kauss 《Plant physiology》1998,117(4):1373-1380
Hypocotyls from etiolated cucumber (Cucumis sativus L.) seedlings were gently abraded at their epidermal surface and cut segments were conditioned to develop competence for H2O2 elicitation. Alkaline hydrolysates of cutin from cucumber, tomato, and apple elicited H2O2 in such conditioned segments. The most active constituent of cucumber cutin was identified as dodecan-1-ol, a novel cutin monomer capable of forming hydrophobic terminal chains. Additionally, the cutin hydrolysates enhanced the activity of a fungal H2O2 elicitor, similar to cucumber surface wax, which contained newly identified alkan-1,3-diols. The specificity of elicitor and enhancement activity was further elaborated using some pure model compounds. Certain saturated hydroxy fatty acids were potent H2O2 elicitors as well as enhancers. Some unsaturated epoxy and hydroxy fatty acids were also excellent H2O2 elicitors but inhibited the fungal elicitor activity. Short-chain alkanols exhibited good elicitor and enhancer activity, whereas longer-chain alkan-1-ols were barely active. The enhancement effect was also observed for H2O2 elicitation by ergosterol and chitosan. The physiological significance of these observations might be that once the cuticle is degraded by fungal cutinase, the cutin monomers may act as H2O2 elicitors. Corrosion of cutin may also bring surface wax constituents in contact with protoplasts and enhance elicitation. 相似文献
15.
16.
Luyang Yu Wang Min Yun He Lingfeng Qin Haifeng Zhang Anton M. Bennett Hong Chen 《The Journal of biological chemistry》2009,284(20):13481-13488
Previously we have shown that tyrosine 718 of ASK1 when phosphorylated is
critical for SOCS1 binding and SOCS1-mediated degradation of ASK1. However,
the kinase and phosphatase responsible for phosphorylation and
dephosphorylation of ASK1 at Tyr-718 are unknown. In this study, we identified
JAK2 and SHP2 as a Tyr-718-specific kinase and phosphatase, respectively.
Interferon-γ (IFN-γ) induced degradation of ASK1 in normal but not
in SOCS1-KO endothelial cells (EC). IFN-γ-induced tyrosine
phosphorylation of ASK1 at Tyr-718 was blocked by a JAK2-specific inhibitor.
IFN-γ enhanced the association between JAK2 and ASK1, and the ASK1-JAK2
complex was labile and was stabilized by the proteasomal inhibitor MG132.
Furthermore, JAK2, but not JAK1, directly bound to and phosphorylated ASK1 at
Tyr-718, leading to an enhanced association of ASK1 with SOCS1 and subsequent
ASK1 degradation. Next, we showed that overexpression of the SH2-containing
protein-tyrosine phosphatase-2 (SHP2) augmented, whereas a
phosphatase-inactive mutant of SHP2 inhibited, TNF-induced ASK1
dephosphorylation. SHP2 associated with ASK1 in response to tumor necrosis
factor in EC. An SHP-2 substrate-trapping mutant formed a complex with
tyrosine-phosphorylated ASK1, suggesting that ASK1 is a direct SHP2 substrate.
Moreover, SHP2 wild type, but not a catalytically inactive mutant, dissociated
SOCS1 from ASK1. IFN-γ-induced ASK1 Tyr(P)-718 was enhanced in mouse EC
deficient in SHP2 (SHP2-KO). In contrast, tumor necrosis factor-induced
dephosphorylation of ASK1 at Tyr(P)-718 and activation of ASK1-JNK signaling,
as well as EC apoptosis, are significantly reduced in SHP2-KO EC. Our data
suggest that JAK2-SOCS1 and SHP2 reciprocally regulate ASK1 phosphorylation
and stability in response to cytokines.Myocardial infarction due to atherosclerosis of coronary arteries remains
the leading cause of death in the United States. It has become clear that
increases in inflammatory mediators represent a common pathogenic mechanism
for atherosclerosis (1). The
vascular cell that normally limits the inflammatory and atherosclerotic
process is the EC.3
Proinflammatory stimuli induce EC dysfunction, which is characterized by an
enhanced sensitivity of vascular cells to proinflammatory and proapoptotic
stimuli. Studies from our laboratory and others have demonstrated that ASK1
(apoptosis signal-regulating kinase-1), a member of MAP3K family
(2,
3), is an effector of
inflammation in EC
(4–8).
Almost all inflammatory stimuli such as tumor necrosis factor-α (TNF),
interleukin-1 (IL-1), and reactive oxygen species activate ASK1. Activated
ASK1 subsequently recruits and activates its downstream target MAP2Ks (MKK3/7
and MKK4/7), which in turn activate MAPKs (JNK and p38). Studies from
ASK1-deficient mice have also linked ASK1 to cardiovascular pathogenesis. ASK1
deletion in mice attenuated angiotensin II-induced cardiac hypertrophy and
remodeling. Neointimal formation due to proliferation of smooth muscle cells
in a cuff injury model is also attenuated by ASK1 deletion in mice
(9,
10).Although the linkage of ASK1 to inflammation is very strong, the mechanism
by which inflammatory stimuli, including TNF, activate ASK1 is not fully
understood. The identification of proteins associated with ASK1 and their
regulation on ASK1 have provided some insights into the mechanism for ASK1
activation. ASK1 is a 170-kDa protein that is composed of an inhibitory
N-terminal domain, an internal kinase domain, and a C-terminal regulatory
domain. One important regulatory mechanism of ASK1 activity is its Ser/Thr
phosphorylation and dephosphorylation by kinases and phosphatases. ASK1 is
basally phosphorylated at Ser-967 by an unidentified kinase, and 14-3-3 binds
to this site and inhibits ASK1 activity
(11,
12). TNF activates ASK1 in
part by dissociating these cellular inhibitors from ASK1
(4,
7). Recently, we have
identified PP2A as a phosphatase in TNF-induced dephosphorylation of ASK1
Ser(P)-967 (13). In addition
to the 14-3-3-binding site, Ser(P)-967, ASK1 is phosphorylated at Ser-83 by
Akt, leading to inhibition of ASK1 activity. In contrast, autophosphorylation
of ASK1 at Thr-838 leads to oligomerization and activation
(14). Phosphorylation of
Thr-845 can be negatively regulated by the phosphatase PP5
(15). Similarly, we found that
the ASK1 autophosphorylation at Thr-813 and Thr-842 also positively regulates
ASK1 signaling (16).In contrast to Ser/Thr phosphorylation, regulation of ASK1 by tyrosine
phosphorylation is less well understood. We have recently shown that ASK1 is
phosphorylated at Tyr-718, and this phosphorylation is critical for the
binding to suppressor of cytokine signaling-1 (SOCS1), a subunit of ubiquitin
ligase responsible for ASK1 degradation
(17). Tyrosine phosphorylation
of ASK1 is up-regulated in response to growth factors and cytokines such as
IFN-γ, whereas this phosphorylation can be down-regulated by TNF
treatment, resulting in ASK1 dissociation from SOCS1. However, the kinase and
phosphatase responsible for phosphorylation and dephosphorylation of ASK1 at
Tyr-718 are not known.The cytoplasmic tyrosine kinase, JAK2, autophosphorylates in response to
growth factors and cytokines, including IFN-γ. JAK2 then activates
cytokine receptors and other cytoplasmic proteins such as the STATs by
phosphorylating their key tyrosine residue. The JAK/STAT pathway can be
regulated by SH2-containing protein-tyrosine phosphatases such as SHP2
(18–20).
SHP2 is ubiquitously expressed and composed of two SH2 domains on the
N-terminal and C-terminal protein-tyrosine phosphatase (PTP) domain. The SH2
domain of SHP2 mediates the association with phosphotyrosine-containing
proteins present on activated receptors as well as on activated JAKs and
STATs; this association triggers activation of the tyrosine phosphatase domain
and subsequent dephosphorylation of substrates. SHP2 signals downstream of
receptor tyrosine kinases and cytokine receptors, and in most cases it serves
to positively transduce signals from these receptors. In other instances SHP2
has been shown to exhibit inhibitory signaling properties by negatively
regulating the JAK-STAT pathway
(19).In this study, we demonstrate that the IFN-γ-activated kinase JAK2
and TNF-activated SHP2 are the tyrosine kinase and phosphatase for Tyr-718 on
ASK1, respectively. The actions of both JAK2 and SHP2 affect protein turnover
of ASK1 and thus regulate ASK1/JNK-dependent proinflammatory and proapoptotic
pathways in EC. 相似文献
17.
Estimating the Excess Investment in
Ribulose-1,5-Bisphosphate
Carboxylase/Oxygenase in
Leaves of Spring Wheat Grown under Elevated
CO2 下载免费PDF全文
Julian C. Theobald Rowan A.C. Mitchell Martin A.J. Parry David W. Lawlor 《Plant physiology》1998,118(3):945-955
Wheat (Triticum aestivum L.) was grown under CO2 partial pressures of 36 and 70 Pa with two N-application regimes. Responses of photosynthesis to varying CO2 partial pressure were fitted to estimate the maximal carboxylation rate and the nonphotorespiratory respiration rate in flag and preceding leaves. The maximal carboxylation rate was proportional to ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) content, and the light-saturated photosynthetic rate at 70 Pa CO2 was proportional to the thylakoid ATP-synthase content. Potential photosynthetic rates at 70 Pa CO2 were calculated and compared with the observed values to estimate excess investment in Rubisco. The excess was greater in leaves grown with high N application than in those grown with low N application and declined as the leaves senesced. The fraction of Rubisco that was estimated to be in excess was strongly dependent on leaf N content, increasing from approximately 5% in leaves with 1 g N m−2 to approximately 40% in leaves with 2 g N m−2. Growth at elevated CO2 usually decreased the excess somewhat but only as a consequence of a general reduction in leaf N, since relationships between the amount of components and N content were unaffected by CO2. We conclude that there is scope for improving the N-use efficiency of C3 crop species under elevated CO2 conditions. 相似文献
18.
Haiqin Lu Hung-Tat Leung Ning Wang William L. Pak Bih-Hwa Shieh 《The Journal of biological chemistry》2009,284(17):11100-11109
Ca2+ modulates the visual response in both vertebrates and
invertebrates. In Drosophila photoreceptors, an increase of
cytoplasmic Ca2+ mimics light adaptation. Little is known regarding
the mechanism, however. We explored the role of the sole Drosophila
Ca2+/calmodulin-dependent protein kinase II (CaMKII) to mediate
light adaptation. CaMKII has been implicated in the phosphorylation of
arrestin 2 (Arr2). However, the functional significance of Arr2
phosphorylation remains debatable. We identified retinal CaMKII by anti-CaMKII
antibodies and by its Ca2+-dependent autophosphorylation. Moreover,
we show that phosphorylation of CaMKII is greatly enhanced by okadaic acid,
and indeed, purified PP2A catalyzes the dephosphorylation of CaMKII.
Significantly, we demonstrate that anti-CaMKII antibodies
co-immunoprecipitate, and CaMKII fusion proteins pull down the catalytic
subunit of PP2A from fly extracts, indicating that PP2A interacts with CaMKII
to form a protein complex. To investigate the function of CaMKII in
photoreceptors, we show that suppression of CaMKII in transgenic flies affects
light adaptation and increases prolonged depolarizing afterpotential
amplitude, whereas a reduced PP2A activity brings about reduced prolonged
depolarizing afterpotential amplitude. Taken together, we conclude that CaMKII
is involved in the negative regulation of the visual response affecting light
adaptation, possibly by catalyzing phosphorylation of Arr2. Moreover, the
CaMKII activity appears tightly regulated by the co-localized PP2A.Visual transduction is the process that converts the signal of light
(photons) into a change of membrane potential in photoreceptors (see Ref.
1 for review). Visual signaling
is initiated upon the activation of rhodopsins by light: light switches on
rhodopsin to generate metarhodopsin, which activates the heterotrimeric
Gq in Drosophila
(2). Subsequently, the
GTP-bound Gαq subunit activates phospholipase Cβ4
encoded by the norpA (no receptor
potential A) gene
(3). Phospholipase Cβ4
catalyzes the breakdown of phosphoinositol 4,5-bisphosphate to generate
diacylglycerol, which or its metabolite has been implicated in gating the
transient receptor potential
(TRP)2 and TRP-like
channels (4,
5). TRP is the major
Ca2+ channel that mediates the light-dependent depolarization
response leading to an increase of cytosolic Ca2+ in
photoreceptors. The rise of intracellular Ca2+ modulates several
aspects of the visual response including activation, deactivation, and light
adaptation (6). For example,
Ca2+ together with diacylglycerol activates a classical protein
kinase C, eye-PKC, which is critical for the negative regulation of visual
signaling by modulating deactivation and light adaptation
(7–11).Light adaptation is the process by which photoreceptors adjust the visual
sensitivity in response to ambient background light by down-regulating
rhodopsin-mediated signaling. Light adaptation can be arbitrarily subdivided
into long term and short term adaptation and may involve multiple regulations
to reduce the efficiency of rhodopsin, G protein, or cation channels. For
example, translocation of both Gq
(12,
13) and TRP-like channels
(14,
15) out of the visual
organelle may contribute to long term adaptation in Drosophila. In
contrast, short term adaptation may be orchestrated by modulating the activity
of signaling proteins by protein kinases. Hardie and co-workers
(16) demonstrated that an
increase of cytoplasmic [Ca2+] mimicked light adaptation, leading
to inhibition of the light-induced current. These authors also showed that
light adaptation is independent of eye-PKC. Thus the effect of cytoplasmic
Ca2+ to control light adaptation is likely mediated via calmodulin
and CaMKII. The contribution of CaMKII to light adaptation has not been
explored.CaMKII is a multimeric Ca2+/calmodulin-dependent protein kinase
that modulates diverse signaling processes
(17). Drosophila
contains one CaMKII gene (18)
that gives rise to at least four protein isoforms
(19). These CaMKII isoforms
share over 85% sequence identities with the α isoform of vertebrate
CaMKII. For insights into the in vivo physiological role of CaMKII,
Griffith et al. (20)
generated transgenic flies (ala) expressing an inhibitory domain of
the rat CaMKII under the control of a heat shock promoter, hsp70.
They demonstrated that, upon heat shock treatment, the overexpression of the
inhibitory peptide resulted in a suppression of the endogenous CaMKII activity
in the transgenic flies (20).
It has been shown that inhibition of CaMKII affects learning and memory
(20) and neuronal functions
(21–24).
In photoreceptors, CaMKII has been implicated in the phosphorylation of the
major visual arrestin, Arr2
(25,
26). However, how
phosphorylation of Arr2 by CaMKII modifies the visual signaling remains to be
elucidated.Here we report the biochemical and electrophysiological analyses of CaMKII
in Drosophila retina. We demonstrate that suppression of CaMKII in
ala1 transgenic flies leads to a phenotype indicative of
defective light adaptation. The ala1 flies also display
greater visual response, suggesting a defect in Arr2. These results support
the notion that CaMKII plays a role in the negative regulation of the visual
response. Our biochemical analyses demonstrate that dephosphorylation of
CaMKII is mediated by protein phosphatase 2A (PP2A). Importantly, we show that
PP2A interacts with CaMKII, indicating that CaMKII forms a stable protein
complex with PP2A to ensure a tight regulation of the kinase activity. Thus a
partial loss of function in PP2A would elevate the CaMKII activity. Indeed, we
show that mts heterozygotes display reduced prolonged depolarizing
potential (PDA) amplitude. This PDA phenotype strongly suggests that Arr2
becomes more effective to terminate the visual signaling in mts
flies. Together, our findings indicate that the ability of Arr2 to terminate
metarhodopsin is increased upon phosphorylation by CaMKII, and the retinal
CaMKII activity is regulated by PP2A. 相似文献
19.