8-bromoguanosino-3--5--cyclic-monophosphorothioate and 6-anilino-5-8-quinolinedione

The phytohormone auxin participates in lateral root formation and primary root growth in plants. The auxin gradient formation is mainly regulated by the direction of polar auxin transport (PAT). PAT requires PIN family proteins, which are auxin transport facilitators and contribute to the establishment and maintenance of auxin gradients and mediate multiple developmental processes. Here, we report the effect of the 3', 5'-cyclic guanosine monophosphate (cGMP), an important second messenger, on postembryonic developmental of Arabidopsis lateral root. We find that enhanced cGMP level through the application of the membrane permeable cGMP analog 8-Br-cGMP, promotes the initiation of lateral root primordia and formation of lateral root. 6-Anilino-5,8-quinolinedione (Ly83583, the guanylate cyclase inhibitor) negatively regulates the process. cGMP also mediates acropetal auxin transport and basipetal auxin transport in the root. We further find that 8-Br-cGMP and Ly83583 change the expression of auxin transport genes and alter the polar localization and expression of PIN1 and PIN2 proteins. Moreover, Ly83583 affects actin organization and localization. Taken together, we propose that cGMP affects auxin transport and auxin gradient through modulation PINs proteins localization and expression. cGMP regulates postembryonic formation of Arabidopsis lateral root through the crosstalk with PAT.

Topics: Actin Cytoskeleton; Aminoquinolines; Arabidopsis; Arabidopsis Proteins; Biological Transport; Cell Membrane Permeability; Cyclic GMP; Gene Expression Regulation, Plant; Genes, Plant; Green Fluorescent Proteins; Indoleacetic Acids; Membrane Transport Proteins; Plant Roots; Plants, Genetically Modified; Seedlings; Thionucleotides

In order to explore the role of nitric oxide (NO) in the control of fetoplacental vascular tone in normal pregnancy we have examined the effects of NO donors on uteroplacental arteries pre-contracted with the vasoconstrictor endothelin-1 (ET-1) or serotonin (5-HT). We have furthermore examined the effects of guanylate cyclase inhibitors on the NO-induced relaxation. Segments of placental arteries (n=102) obtained from 39 placentas immediately after delivery were mounted in organ baths and superfused with Krebs-Ringer solution at 37 degrees C. The vessel segments were exposed to drugs for various intervals and the tension was recorded isometrically and registered on a polygraph. Cyclic guanosine monophosphate (cGMP) analysis was performed after extraction of vessel segments using a specific radioimmunoassay. The placental artery segments responded to ET-1 and 5-HT with a dose-dependent vasoconstriction. After pre-contraction with ET-1 (10(-7) M) or 5-HT (10(-6) M), the vessels relaxed in response to the NO donors glyceryltrinitrate (GTN) (10(-6) M) and S-nitroso-N-acetyl-penicillamine (SNAP) (10(-5) M). In the presence of the non-specific guanylate cyclase inhibitor LY 83583 (10(-6) M), the vessels responded with a small contraction. In the presence of the soluble guanylate cyclase (sGC) inhibitor 1H[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) the non-treated vessels responded with a relaxation. 1H[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one gave no obvious relaxation in pre-contracted vessels. Addition of 8-Br-cGMP, the cell-permeant analogue of cGMP, with or without pre-contraction had no effect on the vessels. Cyclic guanosine monophosphate analysis showed that GTN treatment caused an increase in cGMP after 12 min. Our results indicate that NO acts as a vasodilator in placental vessels. The cGMP-dependent mechanisms may be involved in NO-induced relaxation but cGMP-independent mechanisms appear also to be involved.

Topics: Adult; Aminoquinolines; Cyclic GMP; Dose-Response Relationship, Drug; Endothelin-1; Female; Humans; Muscle, Smooth, Vascular; Nitric Oxide; Nitric Oxide Donors; Nitroglycerin; Placenta; Placental Circulation; Pregnancy; S-Nitroso-N-Acetylpenicillamine; Serotonin; Signal Transduction; Superoxide Dismutase; Thionucleotides; Vasoconstriction; Vasoconstrictor Agents; Vasodilation

Long-term potentiation (LTP) in hippocampus is a type of synaptic plasticity that is thought to be involved in learning and memory. Several lines of evidence suggest that LTP involves 3',5'-cyclic GMP (cGMP), perhaps as an activity-dependent presynaptic effector of one or more retrograde messengers (refs 2-12, but see ref. 13). However, previous results are also consistent with postsynaptic effects of cGMP. This is difficult to test in hippocampal slices, but more rigorous tests are possible in dissociated cell culture. We have therefore developed a reliable method for producing N-methyl-D-aspartate (NMDA) receptor-dependent LTP at synapses between individual hippocampal pyramidal neurons in culture. We report that inhibitors of guanylyl cyclase or of cGMP-dependent protein kinase block potentiation by either tetanic stimulation or low-frequency stimulation paired with postsynaptic depolarization. Conversely, application of 8-Br-cGMP to the bath or injection of cGMP into the presynaptic neuron produces activity-dependent long-lasting potentiation. The potentiation by cGMP involves an increase in transmitter release that is in part independent of changes in the presynaptic action potential. These results support a presynaptic role for cGMP in LTP.

Topics: Action Potentials; Aminoquinolines; Animals; Cells, Cultured; Cyclic GMP; Guanylate Cyclase; Long-Term Potentiation; Magnesium; Neurons; Neurotransmitter Agents; Presynaptic Terminals; Pyramidal Cells; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Synapses; Thionucleotides