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Substantial spine loss in striatal medium spiny neurons (MSNs) and abnormal behaviors are common features of Parkinson's disease (PD). The caudate putamen (CPu) mainly contains MSNs expressing dopamine D1 receptor (dMSNs) and dopamine D2 receptor (iMSNs) exerting critical effects on motor and cognition behavior. However, the molecular mechanisms contributing to spine loss and abnormal behaviors in dMSNs and iMSNs under parkinsonian state remain unknown. In the present study, we revealed that Cell division control protein 42 (Cdc42) signaling was significantly decreased in the caudate putamen (CPu) in parkinsonian mice. In addition, overexpression of constitutively active Cdc42 in the CPu reversed spine abnormalities and improved the behavior deficits in parkinsonian mice. Utilizing conditional dopamine D1 receptor (D1R) or D2 receptor (D2R) knockout mice, we found that such a decrease under parkinsonian state was further reduced by conditional knockout of the D2R but not D1R. Moreover, the thin spine loss in iMSNs and deficits in motor coordination and cognition induced by conditional knockout of D2R were reversed by overexpression of constitutively active Cdc42 in the CPu. Additionally, conditional knockout of Cdc42 from D2R‐positive neurons in the CPu was sufficient to induce spine and behavior deficits similar to those observed in parkinsonian mice. Overall, our results indicate that impaired Cdc42 signaling regulated by D2R plays an important role in spine loss and behavioral deficits in PD. [ABSTRACT FROM AUTHOR]

Plasmid mobilization is important for environments. However, the effects of rhizospheres and root exudates on plasmid mobilization have received little attention. To address this problem, mobilization of the pSUP106 plasmid by a TOL-like plasmid from Pseudomonas fluorescens P13 into rifampicin-resistant P13 cells was investigated by biparental and triparental matings in the rhizosphere soils of maize seedlings and bulk soils. Mobilization frequencies were higher in the rhizosphere than in bulk soils. Plasmid mobilization frequencies decreased with vertical and horizontal distance away from plant roots. Furthermore, plasmid mobilization frequencies increased with growing contents of root exudates and artificial root exudate (ARE) of maize seedlings for 1 or 5 d of incubation time; however, donor and recipient population remained basically stable for all contents. Individual components of the exudates failed to promote mobilization of pSUP106 but a combination of sugars and amino acids of the exudates did. Removal of individual components from the ARE reduced the plasmid mobilization-promoting activity but simultaneous removal of several components destroyed the plasmid mobilization. All the data suggest that the rhizosphere of maize seedlings promoted the mobilization of the pSUP106 plasmid by the TOL-like plasmid and that root exudate of maize seedlings was the important driver of plasmid mobilization. The individual components of root exudates were necessary to increase plasmid mobilization but their combination was important for plasmid mobilization. [ABSTRACT FROM AUTHOR]