A ras-related small GTP-binding protein, RabE1c, regulates stomatal movements and drought stress responses by mediating the interaction with ABA receptors.

Drought represents a leading constraint over crop productivity worldwide. The plant response to this stress is centered on the behavior of the cell membrane, where the transduction of abscisic acid (ABA) signaling occurs. Here, the Ras-related small GTP-binding protein RabE1c has been shown able to bind to an ABA receptor in the Arabidopsis thaliana plasma membrane, thereby positively regulating ABA signaling. RabE1c is highly induced by drought stress and expressed abundantly in guard cells. In the loss-of-function rabe1c mutant, both stomatal closure and the whole plant drought stress response showed a reduced sensitivity to ABA treatment, demonstrating that RabE1c is involved in the control over transpirative water loss through the stomata. Impairment of RabE1c's function suppressed the accumulation of the ABA receptor PYL4. The over-expression of RabE1c in A. thaliana enhanced the plants' ability to tolerate drought, and a similar phenotypic effect was achieved by constitutively expressing the gene in Chinese cabbage (Brassica rapassp. pekinensis). The leading conclusion was that RabE1c promotes the degradation of PYL4, suggesting a possible genetic strategy to engineer crop plants to better withstand drought stress.

Reversible conversion between graphene nanosheets and graphene nanoscrolls at room temperature.

In this paper, the reversible conversion between pristine graphene nanosheets and pristine graphene nanoscrolls at room temperature was reported. The graphene nanosheets were rolled up into the graphene nanoscrolls by silver nitrate in ethanol solution, and the fabricated graphene nanoscrolls were unfolded back to the graphene nanosheets in ethanol solution by adding ammonium hydroxide. The dynamic conversion state of the process was confirmed by the morphology of the intermediate samples captured using an optical microscope and scanning electron microscope. Also, AFM, TEM and Raman spectroscopy displayed that the graphene transformed from its nanoscrolls remained the structure and morphology of the started graphene. The reason for the formation of the nanoscrolls was assigned to the silver cyanide particles generated on the edge of the graphene. The freshly formed silver cyanide caused the unbalanced energy of the graphene surface by changing the pi electron distribution and triggered off the graphene to roll up. The unfolding of the graphene nanoscrolls back to the graphene nanosheets was attributed to the removal of the silver cyanide by the ammonia via forming the complex. This reversible conversion might be a novel and facile approach to make graphene nanoscrolls and to store the graphene. Also, it may bring new sight to the conversion research between two-dimension and one-dimension materials.

Mitochondrial pyruvate carrier 1 mediates abscisic acid-regulated stomatal closure and the drought response by affecting cellular pyruvate content in Arabidopsis thaliana.

BACKGROUND: Stomata are micropores surrounded by pairs of guard cells, and their opening is finely controlled to balance water vapor loss as transpiration and CO2 absorption for photosynthesis. The regulatory signaling network for stomatal movement is complicated, and increasing numbers of new genes have been shown to be involved in this process. Our previous study indicated that a member of the plant putative mitochondrial pyruvate carrier (MPC) family, NRGA1, is a negative regulator of guard cell abscisic acid (ABA) signaling. In this study, we identified novel physiological roles of pyruvate and MPC1, another member of the MPC family, in the regulation of stomatal closure in Arabidopsis. RESULTS: Loss-of-function mutants of MPC1 (mpc1) were hypersensitive to ABA-induced stomatal closure and ABA-activated guard cell slow-type anion currents, and showed a reduced rate of water loss upon drought treatment compared with wild-type plants. In contrast, plants overexpressing MPC1 showed a hyposensitive ABA response and increased sensitivity to drought stress. In addition, mpc1 mutants accumulated more pyruvate after drought or ABA treatment. The increased pyruvate content also induced stomatal closure and activated the slow-type anion channels of guard cells, and this process was dependent on the function of RbohD/F NADPH oxidases and reactive oxygen species concentrations in guard cells. CONCLUSIONS: Our findings revealed the essential roles of MPC1 and pyruvate in stomatal movement and plant drought resistance.

Inhibition of morphine tolerance by MrgC receptor via modulation of interleukin-1ß and matrix metalloproteinase 9 in dorsal root ganglia in rats.

Opiate tolerance is a critical issue in pain management. Previous studies show that activation of Mas-related gene (Mrg) C receptor can modulate the development of morphine tolerance. This study was designed to investigate the underlying mechanism(s). Intrathecal (i.t.) administration of morphine (20µg) increased the expression of interleukin-1ß (IL-1ß) and matrix metalloproteinase-9 (MMP-9) in small- and medium-sized neurons in dorsal root ganglia (DRG). Co-administration of bovine adrenal medulla 8-22 (BAM8-22), a selective MrgC receptor agonist, via i.t. route inhibited the increase of IL-1ß and MMP-9 in the DRG. Exposure of DRG cultures to morphine (3.3µM) for 3 or 5 days, but not for 1 day, induced an increase in MMP-9 mRNA expression. The treatment with BAM8-22 (10nM) for 20, 40 or 60min abolished chronic (5 days) morphine-induced increase of MMP-9 mRNA in the cultured DRG. The treatment with BAM8-22 for 1h inhibited chronic morphine-induced increase of MMP-9 and IL-1ß mRNA in DRG but these effects were abolished by MrgC receptor antibody. The treatment with BAM8-22 for 24 and 72h respectively inhibited and enhanced morphine-induced expression of MMP-9 and IL-1ß mRNA in the cultured DRG. The BAM8-22-induced inhibition and enhancement were abolished by MrgC receptor antibody. The results suggest that the inhibition of IL-1ß and MMP-9 expressions in DRG underlain the modulation of morphine tolerance by the acute activation of MrgC receptors. The chronic activation of MrgC receptors can facilitate morphine-induced increase of MMP-9 and IL-1ß expressions in DRG.

IDL6-HAE/HSL2 impacts pectin degradation and resistance to Pseudomonas syringae pv tomato DC3000 in Arabidopsis leaves.

Plant cell walls undergo dynamic structural and chemical changes during plant development and growth. Floral organ abscission and lateral root emergence are both accompanied by cell-wall remodeling, which involves the INFLORESCENCE DEFICIENT IN ABSCISSION (IDA)-derived peptide and its receptors, HAESA (HAE) and HAESA-LIKE2 (HSL2). Plant cell walls also act as barriers against pathogenic invaders. Thus, the cell-wall remodeling during plant development could have an influence on plant resistance to phytopathogens. Here, we identified IDA-like 6 (IDL6), a gene that is prominently expressed in Arabidopsis leaves. IDL6 expression in Arabidopsis leaves is significantly upregulated when the plant is suffering from attacks of the bacterial Pseudomonas syringae pv. tomato (Pst) DC3000. IDL6 overexpression and knockdown lines respectively decrease and increase the Arabidopsis resistance to Pst DC3000, indicating that the gene promotes the Arabidopsis susceptibility to Pst DC3000. Moreover, IDL6 promotes the expression of a polygalacturonase (PG) gene, ADPG2, and increases PG activity in Arabidopsis leaves, which in turn reduces leaf pectin content and leaf robustness. ADPG2 overexpression restrains Arabidopsis resistance to Pst DC3000, whereas ADPG2 loss-of-function mutants increase the resistance to the bacterium. Pst DC3000 infection elevates the ADPG2 expression partially through HAE and HSL2. Taken together, our results suggest that IDL6-HAE/HSL2 facilitates the ingress of Pst DC3000 by promoting pectin degradation in Arabidopsis leaves, and Pst DC3000 might enhance its infection by manipulating the IDL6-HAE/HSL2-ADPG2 signaling pathway.