The chloroplast division mutant caa33 of Arabidopsis thaliana reveals the crucial impact of chloroplast homeostasis on stress acclimation and retrograde plastid-to-nucleus signaling

Retrograde plastid-to-nucleus signaling tightly controls and coordinates the nuclear and plastid gene expression that is required for plastid biogenesis and chloroplast activity. As chloroplasts act as sensors of environmental changes, plastid-derived signaling also modulates stress responses of plants by transferring stress-related signals and altering nuclear gene expression. Various mutant screens have been undertaken to identify constituents of plastid signaling pathways. Almost all mutations identified in these screens target plastid-specific but not extraplastidic functions. They have been suggested to define either genuine constituents of retrograde signaling pathways or components required for the synthesis of plastid signals. Here we report the characterization of the constitutive activator of AAA-ATPase (caa33) mutant, which reveals another way of how mutations that affect plastid functions may modulate retrograde plastid signaling. caa33 disturbs a plastid-specific function by impeding plastid division, and thereby perturbing plastid homeostasis. This results in preconditioning plants by activating the expression of stress genes, enhancing pathogen resistance and attenuating the capacity of the plant to respond to plastid signals. Our study reveals an intimate link between chloroplast activity and the susceptibility of the plant to stress, and emphasizes the need to consider the possible impact of preconditioning on retrograde plastid-to-nucleus signaling.     

Vapor of Volatile Oils from Litsea cubeba Seed Induces Apoptosis and Causes Cell Cycle Arrest in Lung Cancer Cells

Non-small cell lung carcinoma (NSCLC) is a major killer in cancer related human death. Its therapeutic intervention requires superior efficient molecule(s) as it often becomes resistant to present chemotherapy options. Here we report that vapor of volatile oil compounds obtained from Litsea cubeba seeds killed human NSCLC cells, A549, through the induction of apoptosis and cell cycle arrest. Vapor generated from the combined oils (VCO) deactivated Akt, a key player in cancer cell survival and proliferation. Interestingly VCO dephosphorylated Akt at both Ser⁴⁷³ and Thr³⁰⁸; through the suppression of mTOR and pPDK1 respectively. As a consequence of this, diminished phosphorylation of Bad occurred along with the decreased Bcl-xL expression. This subsequently enhanced Bax levels permitting the release of mitochondrial cytochrome c into the cytosol which concomitantly activated caspase 9 and caspase 3 resulting apoptotic cell death. Impairment of Akt activation by VCO also deactivated Mdm2 that effected overexpression of p53 which in turn upregulated p21 expression. This causes enhanced p21 binding to cyclin D1 that halted G1 to S phase progression. Taken together, VCO produces two prong effects on lung cancer cells, it induces apoptosis and blocked cancer cell proliferation, both occurred due to the deactivation of Akt. In addition, it has another crucial advantage: VCO could be directly delivered to lung cancer tissue through inhalation.     

Synthesis, anticonvulsant activity, and neuropathic pain-attenuating activity of N-benzyl 2-amino-2-(hetero)aromatic acetamides

N-Benzyl 2-acetamido-2-substituted acetamides, where the 2-substituent is a (hetero)aromatic moiety, are potent anticonvulsants. We report the synthesis and whole animal pharmacological evaluation of 16 analogues where the terminal 2-acetyl group was removed to give the corresponding primary amino acid derivatives (PAADs). Conversion to the PAAD structure led to a substantial drop in seizure protection in animal tests, demonstrating the importance of the N-acetyl moiety for anticonvulsant activity. However, several of the PAADs displayed notable pain-attenuating activities in a mouse model.     

Immobilization of glucansucrase for the production of gluco-oligosaccharides from Leuconostoc mesenteroides

Glucansucrase from Leuconostoc mesenteroides was immobilized in 1?% (w/v) with sodium alginate to produce oligosaccharides. Glucansucrase gave three activity bands of approx. 240, 178, and 165?kDa after periodic acid-Schiff staining with sucrose. The immobilized enzyme had 40?% activity after ten batch reactions at 30?°C and 75?% activity after a month of storage at 4?°C, which is six times more stable than the free enzyme. Immobilized enzyme was more stable at lower (3.5?4.5) and higher (6.5?7.0) pH ranges and higher temperatures (35?40?°C) compared with the free enzyme. Immobilized and free glucansucrase were employed in the acceptor reaction with maltose and each produced gluco-oligosaccharide ranging from trisaccharides to homologous pentasaccharides.     

Modulation of 1O2-mediated retrograde signaling by the PLEIOTROPIC RESPONSE LOCUS 1 (PRL1) protein, a central integrator of stress and energy signaling

Shortly after the release of singlet oxygen (¹O₂) in chloroplasts, changes in nuclear gene expression occur in the conditional flu mutant of Arabidopsis that reveal a rapid transfer of signals from the plastid to the nucleus. Extensive genetic screens aimed at identifying constituents involved in ¹O₂-mediated plastid-to-nucleus signaling have failed to identify extraplastidic signaling components. This finding suggests that ¹O₂-mediated signals are not translocated to the nucleus via a single linear pathway, but rather through a signaling network that is difficult to block by single mutations. The complexity of this signaling network has been tackled by mutagenizing a transgenic flu line expressing the luciferase reporter gene under the control of the promoter of a ¹O₂-responsive AAA-ATPase gene (At3g28580) and isolating second site mutants that constitutively express the reporter gene at a high level. One of the mutants was shown by map-based cloning and sequencing to contain a single amino acid change in the PLEIOTROPIC RESPONSE LOCUS 1 (PRL1) protein. PRL1 suppresses the expression of AAA-ATPase and other ¹O₂-responsive genes. PRL1 seems to play a major role in modulating responses of plants to environmental changes by interconnecting ¹O₂-mediated retrograde signaling with other signaling pathways.     

Anti-diabetic effects of vanadium(III, IV, V)–chlorodipicolinate complexes in streptozotocin-induced diabetic rats

Vanadium(III, IV, V)–chlorodipicolinate (dipic-Cl) complexes, including H[V^III(dipic-Cl)₂] · 5H₂O (V₃dipic-Cl), V^IVO(dipic-Cl)(H₂O)₂ (V₄dipic-Cl) and K[V^VO₂(dipic-Cl)] (V₅dipic-Cl), were prepared with the indicated oxidation states. Our aim was to evaluate the anti-diabetic effects of V₃dipic-Cl, V₄dipic-Cl and V₅dipic-Cl in streptozotocin-induced diabetic rats. Vanadium complexes were orally administered to diabetic rats at concentrations of 0.1–0.3 mg/ml in the drinking water. We found that vanadium–chlorodipicolinate (V–dipic-Cl) complexes at the concentration of 0.1 mg/ml did not exhibit blood glucose-lowering effects when administered to diabetic rats for 20 days. However, the levels of fasting blood glucose in diabetic rats were decreased after treatment with 0.3 mg/ml of V₄dipic-Cl and V₅dipic-Cl complexes for the following 20 days. Although administration of both V₄dipic-Cl and V₅dipic-Cl significantly lowered diabetic hyperglycemia, the vanadium intake from administration of V₄dipic-Cl is nearly 1.5-fold greater compared to that of V₅dipic-Cl. Treatment with the H₂dipic-Cl ligand and all three V–dipic-Cl complexes significantly lowered serum cholesterol, while administration of the V₅dipic-Cl complex lowered serum cholesterol significantly more than administration of the ligand alone. Treatment with ligand alone did not have an effect on serum triglyceride, while administration of the V₄dipic-Cl and V₅dipic-Cl significantly lowered the elevated serum triglyceride associated with diabetes. Oral administration of the ligand and all V–dipic-Cl complexes did significantly lower diabetes elevated serum alkaline phosphatase. Treatment with H₂dipic-Cl ligand and V₄dipic-Cl and V₅dipicCl significantly lowered diabetes elevated aspartate amino transferase. These results indicate that the health of the treated animals did not seem to be further compromised compared to that of diabetic animals. In addition, oral administration of H₂dipic-Cl, V₃dipic-Cl, V₄dipic-Cl and V₅dipic-Cl did not alter diabetic serum creatinine and blood urea nitrogen levels, suggesting no significant side effects of vanadium treatment on renal functions at the dose of 0.3 mg/ml in diabetic rats. The results presented here suggest that the anti-diabetic effects of treatment with V–dipic-Cl complexes were likely associated in part with the oxidation state of vanadium.     

Characterization of cellulose degrading bacteria from the larval gut of the white grub beetle Lepidiota mansueta (Coleoptera: Scarabaeidae)

The goal of this study is to identify and characterize the cellulose degrading microorganisms in the larval gut of the white grub beetle, Lepidiota mansueta. Thirty bacterial strains were isolated and tested for cellulolytic activity using soluble carboxymethyl cellulose (CMC) degrading assays. Of these strains, five (FGB1, FB2, MB1, MB2, and HB1) degrade cellulose. Cellulolytic activity was determined based on formation of clear zone and cellulolytic index on CMC plate media. The highest cellulolytic index (2.14) was found in FGB1. Partial 16S rDNA sequencing, morphological, and biochemical tests were used to identify and characterize the five isolates, all Citrobacter sp. (Enterobacteriaceae). This study identifies new cellulose degrading microorganisms from the larval gut of L. mansueta. The significance of identifying these strains lies in possible application in cellulose degradation.     

Impairment of ascorbic acid’s anti-oxidant properties in confined media: Inter and intramolecular reactions with air and vanadate at acidic pH

The anti-oxidant properties of l-ascorbic acid were investigated in the confined medium produced by a sodium bis(2-ethylhexyl)sulfosuccinate (aerosol-OT, AOT) self-assembled reverse micelle. Using ¹H–¹H NOESY (proton-proton 2D nuclear overhauser enhancement correlation spectroscopy) NMR spectroscopy, the location of ascorbic acid was investigated and found to be at the AOT-interface in contrast to earlier studies where the ascorbate was assumed to be in the water pool in these microemulsions. The reaction of ascorbic acid with oxygen was investigated using EPR spectroscopy. A delocalized monoanionic ascorbate radical was observed in microemulsions prepared from pH 5.6 stock solutions. This is in contrast to studies carried out in aqueous media where no radical formation was observed. The oxidation of ascorbic acid by aqueous V(V) was investigated in reverse micelles. Modest changes in the kinetic parameters were observed for this system compared to that in water. Details of these reactions were examined and can be summarized as the microemulsion solvating and stabilizing reactive intermediates via rate inhibition or enhancement. The inhibition of the oxidation is due to solvation stabilization of ascorbic acid in microemulsion media. Since ascorbate is a valuable marker of oxidative stress, our results suggest that compartmentization can modify the stabilization of the ascorbate radical and the changes in properties could be important in biological systems.     

Synthesis and cytotoxic activity of novel quinazolino-beta-carboline-5-one derivatives

A novel series of quinazolino-beta-carbolinone derivatives was synthesized and evaluated for their in vitro and in vivo anticancer activity. Many compounds have shown good in vitro activity in the range 1-8 microM concentration. Three of the compounds were further tested in nude mice bearing HT-29 colon cancer xenografts.