Effect of urban pollution on 4-coumarate: CoA ligase and flavonoid accumulation in Berberis thunbergii

Flavonoids are polyphenolic compounds commonly found in plants and they play an important role in stress tolerance. They have the capacity to chelate heavy metals andscavenge free radicals. Urban pollution causes oxidative stress in plants and flavonoids may protect cells against the negative effect of free radicals. In this study levels of anthocyanins andflavonols and4-coumarate:CoA ligase (4CL) activity were determinedin Berberis thunbergii (DC.) plants grown in pollutedandresid ential areas in the city of Poznań. The results showedsignificantly higher accumulation of anthocyanins andstimulation of 4CL activity in plants from the contaminatedsites in comparison to the control plants. Probably the activation of the phenylpropanoidpathway was a response to stress caused by urban pollution

Dark-induced senescence of barley leaves involves activation of plastid transglutaminases

Transglutaminases (E.C. 2.3.2.13) catalyze the post-translational modification of proteins by establishing \u3b5-(\u3b3-glutamyl) lysine isopeptide bonds and by the covalent conjugation of polyamines to endo-glutamyl residues of proteins. In light of the confirmed role of transglutaminases in animal cell apoptosis and only limited information on the role of these enzymes in plant senescence, we decided to investigate the activity of chloroplast transglutaminases (ChlTGases) and the fate of chloroplast-associated polyamines in Hordeum vulgare L. 'Nagrad' leaves, where the senescence process was induced by darkness (day 0) and continued until chloroplast degradation (day 12). Using an anti-TGase antibody, we detected on a subcellular level, the ChlTGases that were associated with destacked/degraded thylakoid membranes, and beginning on day 5, were also found in the stroma. Colorimetric and radiometric assays revealed during senescence an increase in ChlTGases enzymatic activity. The MS/MS identification of plastid proteins conjugated with exogenous polyamines had shown that the ChlTGases are engaged in the post-translational modification of proteins involved in photosystem organization, stress response, and oxidation processes. We also computationally identified the cDNA of Hv-Png1-like, a barley homologue of the Arabidopsis AtPng1 gene. Its mRNA level was raised from days 3 to 10, indicating that transcriptional regulation controls the activity of barley ChlTGases. Together, the presented results deepen our knowledge of the mechanisms of the events happened in dark-induced senescence of barley leaves that might be activation of plastid transglutaminases

Fhit proteins can also recognize substrates other than dinucleoside polyphosphates

AbstractWe show here that Fhit proteins, in addition to their function as dinucleoside triphosphate hydrolases, act similarly to adenylylsulfatases and nucleoside phosphoramidases, liberating nucleoside 5′-monophosphates from such natural metabolites as adenosine 5′-phosphosulfate and adenosine 5′-phosphoramidate. Moreover, Fhits recognize synthetic nucleotides, such as adenosine 5′-O-phosphorofluoridate and adenosine 5′-O-(γ-fluorotriphosphate), and release AMP from them. With respect to the former, Fhits behave like a phosphodiesterase I concomitant with cleavage of the P–F bond. Some kinetic parameters and implications of the novel reactions catalyzed by the human and plant (Arabidopsis thaliana) Fhit proteins are presented