Regulation of adaptive growth decisions via phosphorylation of the TRAPPII complex in Arabidopsis

Plants often adapt to adverse or stress conditions via differential growth. The trans-Golgi network (TGN) has been implicated in stress responses, but it is not clear in what capacity it mediates adaptive growth decisions. In this study, we assess the role of the TGN in stress responses by exploring the previously identified interactome of the Transport Protein Particle II (TRAPPII) complex required for TGN structure and function. We identified physical and genetic interactions between AtTRAPPII and shaggy-like kinases (GSK3/AtSKs) and provided in vitro and in vivo evidence that the TRAPPII phosphostatus mediates adaptive responses to abiotic cues. AtSKs are multifunctional kinases that integrate a broad range of signals. Similarly, the AtTRAPPII interactome is vast and considerably enriched in signaling components. An AtSK-TRAPPII interaction would integrate all levels of cellular organization and instruct the TGN, a central and highly discriminate cellular hub, as to how to mobilize and allocate resources to optimize growth and survival under limiting or adverse conditions.

Regulation of adaptive growth decisions via phosphorylation of the TRAPPII complex in Arabidopsis

Plants often adapt to adverse or stress conditions via differential growth. The trans-Golgi Network (TGN) has been implicated in stress responses, but it is not clear in what capacity it mediates adaptive growth decisions. In this study, we assess the role of the TGN in stress responses by exploring the interactome of the Transport Protein Particle II (TRAPPII) complex, required for TGN structure and function. We identified physical and genetic interactions between TRAPPII and shaggy-like kinases (GSK3/AtSKs). Kinase assays and pharmacological inhibition provided in vitro and in vivo evidence that AtSKs target the TRAPPII-specific subunit AtTRS120/TRAPPC9. GSK3/AtSK phosphorylation sites in AtTRS120/TRAPPC9 were mutated, and the resulting AtTRS120 phosphovariants subjected to a variety of single and multiple stress conditions in planta . The non-phosphorylatable TRS120 mutant exhibited enhanced adaptation to multiple stress conditions and to osmotic stress whereas the phosphomimetic version was less resilient. Higher order inducible trappii atsk mutants had a synthetically enhanced defect in root gravitropism. Our results suggest that the TRAPPII phosphostatus mediates adaptive responses to abiotic cues. AtSKs are multifunctional kinases that integrate a broad range of signals. Similarly, the TRAPPII interactome is vast and considerably enriched in signaling components. An AtSK-TRAPPII interaction would integrate all levels of cellular organization and instruct the TGN, a central and highly discriminate cellular hub, as to how to mobilize and allocate resources to optimize growth and survival under limiting or adverse conditions.

Interactions between Transport Protein Particle (TRAPP) complexes and Rab GTPases in Arabidopsis

Transport Protein Particle II (TRAPPII) is essential for exocytosis, endocytosis, protein sorting and cytokinesis. In spite of a considerable understanding of its biological role, little information is known about Arabidopsis TRAPPII complex topology and molecular function. In this study, independent proteomic approaches initiated with TRAPP components or Rab-A GTPase variants converge on the TRAPPII complex. We show that the Arabidopsis genome encodes the full complement of 13 TRAPPC subunits, including four previously unidentified components. A dimerization model is proposed to account for binary interactions between TRAPPII subunits. Preferential binding to dominant negative (GDP-bound) versus wild-type or constitutively active (GTP-bound) RAB-A2a variants discriminates between TRAPPII and TRAPPIII subunits and shows that Arabidopsis complexes differ from yeast but resemble metazoan TRAPP complexes. Analyzes of Rab-A mutant variants in trappii backgrounds provide genetic evidence that TRAPPII functions upstream of RAB-A2a, allowing us to propose that TRAPPII is likely to behave as a guanine nucleotide exchange factor (GEF) for the RAB-A2a GTPase. GEFs catalyze exchange of GDP for GTP; the GTP-bound, activated, Rab then recruits a diverse local network of Rab effectors to specify membrane identity in subsequent vesicle fusion events. Understanding GEF-Rab interactions will be crucial to unravel the co-ordination of plant membrane traffic.

An Assessment of Oxidant/Antioxidant Status and Oxidative Stress Index Levels in Patients with Carbon Monoxide Poisoning

Objective

The purposes of this study is to evaluate the variations of total antioxidant status (TAS) and total oxidant status (TOS) levels in the treatment process of carbon monoxide poisoning (COP) and to learn more about the pathophysiology of COP.

Methods

Between 2011 and 2012, 113 patients were admitted to our emergency department with acute COP, and 50 healthy volunteers were used as a control group in this study. Serum, plasma and erythrocyte components were prepared for all the COP patients on admission. They were repeated at the 90th and 180th minute of treatment. The samples were taken once from the control group. Serum oxidant/antioxidant status levels and carboxyhaemoglobin (COHb) were measured. Ratio of TOS to TAS, known as oxidative stress index (OSI) was calculated.

Results

No correlation was observed among age, gender, COHb level, with the levels of TAS, TOS, and OSI. Admission levels of TOS and OSI in patients with COP were higher than that observed at 90th minutes (p<0.001). These values were also higher in COP patients compared to control group (p<0.001). On the other hand, no statistical differences were observed in TAS levels between the study and control groups (p>0.05).

Conclusions

Our results show that serum TOS and OSI levels increase in COP patients. Oxidative stress should play a role in the pathophysiology of COP. (Hong Kong j.emerg.med. 2013;20:352-358)

Virus safety of plasma products using 20 nm instead of 15 nm filtration as virus removing step

During the manufacture of human plasma derivatives, a series of complementary measures are undertaken to prevent transmission of blood-borne viruses. Virus filtration using 15 nm (Planova15N) filters has successfully been implemented in manufacturing processes for various plasma derivatives primarily because virus filtration is a technique, mild for proteins, that can effectively remove even small non-lipid-enveloped viruses, such as HAV and parvovirus B19. However, the use of 15 nm filters has limitations with regard to protein capacity of the filters and the process flow, resulting in an expensive manufacturing step. Therefore, studies were performed to test whether the use of 20 nm (Planova20N) filters, having different characteristics compared to 15 nm filters, can be an alternative for the use of 15 nm filters. It is shown that 20 nm filtration can be an alternative for 15 nm filtration. However, the virus removal capacity of the 20 nm filters depends on the plasma product that is filtered. Therefore, an optimisation study must be performed with regard to process parameters such as pressure, pH and protein concentration for each plasma product. In this study, using optimised conditions, the virus removal capacity of 20 nm filters appears to be comparable or even better when compared to that of 15 nm filters.

Incidence of HTLV-I/II infection in seronegative high-risk individuals

The frequency of human T-cell lymphotropic virus types I and II (HTLV-I/II) polymerase chain reaction (PCR) reactivity was studied in two groups of high-risk individuals in Amsterdam: hard drug users and heterosexual outpatients of the sexual transmitted diseases (STD) clinic. Both groups were seronegative as determined by enzyme-linked immunosorbent assay (ELISA), Western blot (WB), and radioimmuno-precipitation assay (RIPA). Detection of HTLV-I and HTLV-II in peripheral blood mononuclear cells (MNC) was performed by PCR, using primer sets indicative for the pol and tax genes. In the hard drug users group (n = 25) no evidence of HTLV-I/II infection was found whereas in the STD group (n = 21) one individual was identified with HTLV-II proviral DNA. Positive reactions in PCR were confirmed only for three seropositive controls after in vitro culture of MNC but not for the PCR-positive, seronegative individual. Virus production in vitro could not be detected by a sensitive HTLV-I antigen capture assay for viral p24gag proteins after in vitro T-cell stimulation of MNC, either from PCR-positive or PCR-seronegative individuals. This suggests again a low viral production rate. It is concluded that infection with HTLV-II can be detected among high-risk seronegative individuals.

T-cell differentiation in the rabbit. II. Con A and PHA response of thymus, spleen and lymph node cells and of thymus subpopulations; influence of dexamethasone treatment

Mitogen-induced proliferation of rabbit lymphocytes from the thymus (Thy), spleen (Spl) and lymph node (LN) was measured by [3H]thymidine incorporation. The various cell suspensions taken from normal animals showed wide differences in their response to Con A and PHA. Cell suspensions taken from steroid-treated animals did not show differences in response. The disappearance of these differences in mitogen reactivity after steroid treatment is caused by a decreased Con A response of LN cells and an increased Con A and PHA response of Thy cells. The results suggest the existence of a steroid-sensitive (Ss). Con A-responsive cell population in LN cells. The mitogen response of untreated and steroid-resistant (SR) Thy cells was further investigated in cell suspensions separated on density gradients and in cell suspensions enriched in, or depleted of cells bearing receptors for Fc (T gamma and T non-gamma, respectively). It is concluded that Ss thymocytes of high density are mitogen non-reactive, and that Ss cells of low and medium density consist of subpopulations of cells reactive to Con A and/or to PHA. Sr thymocytes still displayed heterogeneity in buoyant density and mitogen responsiveness. Heavy cells and T gamma cells (10% of the Sr cells were T gamma) showed a lowered mitogen response. The results are discussed in relation to data describing the localization of the cell types which differ in mitogen reactivity. The results support the idea of two differentiation pathways, one for Ss and the other for Sr thymocytes.

Genetic control of the conversion of dihydroflavonols into flavonols and anthocyanins in flowers of Petunia hybrida

Petunia hybrida mutants, homozygous recessive for one of the genes An1, An2, An6, or An9 do not show anthocyanin synthesis in in vitro complementation experiments per se (see also Kho et al. 1977). Extracts of flowers of these mutants all provoke anthocyanin synthesis in isolated petals of an an3an3 mutant. Mutants homozygous recessive for one of the genes An1, An2, An6, or An9 and homozygous recessive for F1 accumulate dihydroflavonols in comparable amounts. The synthesis of dihydromyricetin is blocked in an1an1 mutants, which indicates a regulating effect of the gene An1 on the gene Hfl. Similar mutants, but dominant for F1, accumulate flavonols (kaempferol and quercetin) instead of dihydroflavonols. Myricetin is accumulated in minor amounts and not at all in an1an1 mutant. Furthermore, the synthesis of this flavonol is not controlled by the gene F1. The synthesis of cyanidin (derivatives) is greatly reduced when flavonols are synthesized (F1 dominant). In mutants dominant for Ht1 and Hf1 and thus able to synthesize cyanidin (derivatives) and delphinidin (derivatives), predominantly delphinidin (derivatives) are synthesized. The results indicate that kaempferol (derivatives), quercetin (derivatives), and delphinidin (derivatives) are the main endproducts of flavonoid biosynthesis in Petunia hybrida.