Actin filaments mediated root growth inhibition by changing their distribution under UV-B and hydrogen peroxide exposure in Arabidopsis

BACKGROUND: UV-B signaling in plants is mediated by UVR8, which interacts with transcriptional factors to induce root morphogenesis. However, research on the downstream molecules of UVR8 signaling in roots is still scarce. As a wide range of functional cytoskeletons, how actin filaments respond to UV-B-induced root morphogenesis has not been reported. The aim of this study was to investigate the effect of actin filaments on root morphogenesis under UV-B and hydrogen peroxide exposure in Arabidopsis. RESULTS: A Lifeact-Venus fusion protein was used to stain actin filaments in Arabidopsis. The results showed that UV-B inhibited hypocotyl and root elongation and caused an increase in H2O2 content only in the root but not in the hypocotyl. Additionally, the actin filaments in hypocotyls diffused under UV-B exposure but were gathered in a bundle under the control conditions in either Lifeact-Venus or uvr8 plants. Exogenous H2O2 inhibited root elongation in a dose-dependent manner. The actin filaments changed their distribution from filamentous to punctate in the root tips and mature regions at a lower concentration of H2O2 but aggregated into thick bundles with an abnormal orientation at H2O2 concentrations up to 2 mM. In the root elongation zone, the actin filament arrangement changed from lateral to longitudinal after exposure to H2O2. Actin filaments in the root tip and elongation zone were depolymerized into puncta under UV-B exposure, which showed the same tendency as the low-concentration treatments. The actin filaments were hardly filamentous in the maturation zone. The dynamics of actin filaments in the uvr8 group under UV-B exposure were close to those of the control group. CONCLUSIONS: The results indicate that UV-B inhibited Arabidopsis hypocotyl elongation by reorganizing actin filaments from bundles to a loose arrangement, which was not related to H2O2. UV-B disrupted the dynamics of actin filaments by changing the H2O2 level in Arabidopsis roots. All these results provide an experimental basis for investigating the interaction of UV-B signaling with the cytoskeleton.

Passive smoking exposure and related risk awareness among adults in Zhengzhou / 预防医学

Objective @#To learn the passive smoking exposure and hazard awareness among the residents aged 18 years and over in Zhengzhou,so as to provide evidence for tobacco control. @*Methods@#By multi-stage stratified and clustered sampling method,the residents aged 18 years and over in Zhengzhou were selected. From June to October in 2018,a questionnaire for risk factors of non-communicable diseases,designed by Chinese Center for Disease Control and Prevention,was used to collect their passive smoking exposure and hazard awareness and then analyzed.@*Results @#A total of 6 793 questionnaires were qualified in 6 809 questionnaires and the effective rate was 99.77%. Among 5 387 non-smokers,2 131 people were exposed to passive smoking,and the crude and standardized rate was 39.56% and 40.14%. The standardized rate of passive smoking exposure was higher in men than in women（42.44% vs. 38.67%,P<0.05）,in rural residents than in urban residents（43.90% vs. 36.62%,P<0.05）,and it decreased with the age increase（P<0.05）. The standardized rate of passive smoking exposure in family,indoor workplace and indoor public place was 30.99%,36.99% and 68.02%,respectively. The standardized awareness rate of “passive smoking exposure may lead to heart disease,lung disease in children and lung cancer in adults” was 56.63%,which was higher in urban rural residents than in rural residents（75.69% vs. 36.33%,P<0.05）. @*Conclusions@#The passive smoking exposure rate was high in Zhengzhou,especially in indoor public places. The awareness of the hazards of passive smoking exposure was scarce, especially in rural residents.