Root discoloration and shoot symptoms in silver birch after Phytophthora infection in vitro.

There are no records of established plant pathogenic Phytophthora species in Finnish forests, but they are likely in the future. Therefore, the effects of Phytophthora inoculations on young, ca. 2-month-old silver birch (Betula pendula) seedling roots and shoots were investigated. Visual inspection of dark discoloration, direct PCR and re-isolation, and detailed root morphology analyses were used to evaluate the effects of Phytophthora inoculation on roots. Symptoms in leaves and stems were also recorded. Phytophthora was successfully re-isolated from 67% of the surface-sterilized roots of inoculated seedlings, but not from the non-inoculated control seedlings. Dark discolorations were found more often in the root segments of inoculated seedlings than in control seedlings. In the Phytophthora-treated seedlings, discoloured root segments were usually linked and found primarily in the main root or lateral roots attached to it, whereas in the control seedlings a few single discoloured root segments were scattered throughout the root systems. The number of root segments was lower in the inoculated than in the control seedlings, indicating root loss after Phytophthora inoculation. In the shoots of inoculated birches, leaf and shoot wilting was observed. The appearance of wilting in shoots without visible dark discoloration in the base of stems indicated that symptoms originated from roots inoculated with Phytophthora.

Rb1, the Primary Active Ingredient in Panax ginseng C.A. Meyer, Exerts Antidepressant-Like Effects via the BDNF-Trkb-CREB Pathway.

Panax ginseng C.A. Meyer (Araliaceae), a popular tonic and dietetic herbal medicine, has been traditionally prescribed in China and other countries to treat affective disorders. The medicinal parts of ginseng, the roots and flower buds, have become increasingly popular as dietary supplements due to the current holistic healthcare trend. We have investigated for the first time the antidepressive actions of the different medicinal parts, namely, the main roots, fibrous roots, and flower buds (in water extract and powder), of garden-cultivated ginseng through behavioral and drug-induced tests in mice. The water extracts, but not the powders of ginseng fibrous roots, flower buds, and main roots (1.5 g of crude drug per kilogram, p.o.), significantly reduced the immobility time in the forced swim test (FST) and tail suspension test (TST); moreover, the water extracts enhanced the 5-hydroxytryptophan (5-HTP)-induced head-twitch response and antagonized the action of reserpine in the mouse. We then explored the antidepressive mechanism of action of the ginsenoside Rb1 (Rb1) related to the brain-derived neurotrophic factor (BDNF) and its downstream proteins in mice exposed to chronic unpredictable mild stress (CUMS). Treatment with Rb1 (20 mg/kg, p.o.) for 21 days significantly attenuated the CUMS-induced decrease in the activities of BDNF, tropomyosin-related kinase B (TrkB), protein kinase B (AKT), extracellular regulatory protein kinase (ERK), and cyclic adenosine monophosphate (cAMP) response element binding protein (CREB) in the mouse hippocampal CA3 region and prefrontal cortex (PFC). Interestingly, treatment with the novel TrkB antagonist ANA-12 (0.5 mg/kg, i.p.) did not alter the level of BDNF but significantly blocked the antidepressive effects of Rb1 on proteins downstream of BDNF in CUMS-treated mice. These results suggest that BDNF-TrkB-CREB signaling may be involved in the antidepressive mechanism of the action of Rb1.