One of the most significant insults that jeopardize cardiomyocyte homeostasis is a surge of reactive oxygen species (ROS) in the failing myocardium. Early growth response factor-1 (Egr-1) has been found to act as a transcriptional regulator in multiple biological processes known to exert deleterious effects on cardiomyocytes. We thus investigated the signaling pathways involved in its regulation by H2O2. Egr-1 mRNA levels were found to be maximally induced after 2 h in H2O2-treated H9c2 cells. Egr-1 respective response at the protein level, was found to be maximally induced after 2 h of treatment with 200 μM H2O2, remaining elevated for 6 h, and declining thereafter. H2O2- induced upregulation of Egr-1 mRNA and protein levels was ablated in the presence of agents inhibiting ERKs pathway (PD98059) and JNKs (SP600125, AS601245). Immunofluorescent experiments revealed H2O2-induced Egr-1 nuclear sequestration to be also ERK- and JNK-dependent. Overall, our results show for the first time the fundamental role of ERKs and JNKs in regulating Egr-1 response to H2O2 treatment in cardiac cells at multiple levels: mRNA, protein and subcellular distribution. Nevertheless, further studies are required to elucidate the specific physiological role of Egr-1 regarding the modulation of gene expression and determination of cell fate., I.-K. S. Aggeli, I. Beis, C. Gaitanaki., and Obsahuje bibliografii a bibliografické odkazy
Prosopis juliflora is a hardy plant tolerant to drought, salinity, extremes of soil pH, and heavy metal stress. We isolated and characterized a photosystem 2 (PS2) gene PsbR (Pj PsbR) and its promoter. Northern analysis for Pj PsbR in P. juliflora leaves under 25 % polyethylene glycol stress showed steady decrease in transcript level at 12, 24, and 48 h after stress application. Under 90 mM H2O2 stress, transcript level dropped drastically at 12 h, but increased again compared to the control at 24 h. A 1.7 kb fragment upstream the 5' UTR of this gene (putative promoter) was isolated and analyzed in silico. Several putative cis-acting DNA elements were identified in this sequence. and G. Suja, A. Parida.
We investigated the physiological effect of night chilling (CN) on potted seedlings of two tropical tree species, Calophyllum polyanthum and Linociera insignis, in Xishuangbanna, southwest China. Seedlings grown under 8, 25, and 50 % daylight for five months were moved to a 4-6 °C cold storage house for three consecutive nights, and returned to the original shaded sites during the day. CN resulted in strong suppression of photosynthesis and stomatal conductance for L. insignis, and reduced photorespiration rates, carboxylation efficiency, and maximum photochemical efficiency of photosystem 2 (PS2) at dawn and midday for both species. CN increased dawn and midday rates of non-photochemical quenching, and the contents of malondialdehyde and H2O2 for both species. CN also induced inactivation or destruction of PS2 reaction centres. The impacts of CN on tropical seedlings increased with the number of CN. Shading could significantly mitigate the adverse effects of CN for both species. After 3-d-recovery, gas exchange and fluorescence parameters for both species returned to pre-treatment levels in most cases. Thus CN induced mainly stomatal limitation of photosynthesis for L. insignis, and non-stomatal limitation for C. polyanthum. C. polyanthum was more susceptible to CN than L. insignis. Fog, which often occurs in Xishuangbanna, could be beneficial to chilling sensitive tropical seedlings in this area through alleviating photoinhibition or photodamage by reducing sunlight. and Y.-L. Feng, K.-F. Cao.