The foliar application of a mixture of semisynthetic chitosan derivatives induces tolerance to water deficit in maize, improving the antioxidant system and increasing photosynthesis and grain yield.

Research has shown that chitosan induces plant stress tolerance and protection, but few studies have explored chemical modifications of chitosan and their effects on plants under water stress. Chitosan and its derivatives were applied (isolated or in mixture) to maize hybrids sensitive to water deficit under greenhouse conditions through foliar spraying at the pre-flowering stage. After the application, water deficit was induced for 15 days. Analyses of leaves and biochemical gas exchange in the ear leaf were performed on the first and fifteenth days of the stress period. Production attributes were also analysed at the end of the experiment. In general, the application of the two chitosan derivatives or their mixture potentiated the activities of the antioxidant enzymes superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase and guaiacol peroxidase at the beginning of the stress period, in addition to reducing lipid peroxidation (malonaldehyde content) and increasing gas exchange and proline contents at the end of the stress period. The derivatives also increased the content of phenolic compounds and the activity of enzymes involved in their production (phenylalanine ammonia lyase and tyrosine ammonia lyase). Dehydroascorbate reductase and compounds such as total soluble sugars, total amino acids, starch, grain yield and harvest index increased for both the derivatives and chitosan. However, the mixture of derivatives was the treatment that led to the higher increase in grain yield and harvest index compared to the other treatments. The application of semisynthetic molecules derived from chitosan yielded greater leaf gas exchange and a higher incidence of the biochemical conditions that relieve plant stress

Proteolysis of the proofreading subunit controls the assembly of Escherichia coli DNA polymerase III catalytic core.

The C-terminal region of the proofreading subunit (\u25b) of Escherichia coli DNA polymerase III is shown here to be labile and to contain the residues (identi\ufb01ed between F187 and R213) responsible for association with the polymerase subunit (\u3b1). We also identify two \u3b1-helices of the polymerase subunit (comprising the residues E311\u2013M335 and G339\u2013D353, respectively) as the determinants of binding to \u25b. The C-terminal region of \u25b is degraded by the ClpP protease assisted by the GroL molecular chaperone, while other factors control the overall concentration in vivo of \u25b. Among these factors, the chaperone DnaK is of primary importance for preserving the integrity of \u25b. Remarkably, inactivation of DnaK confers to Escherichia coli inviable phenotype at 42 \ub0C, and viability can be restored over-expressing \u25b. Altogether, our observations indicate that the association between \u25b and \u3b1 subunits of DNA polymerase III depends on small portions of both proteins, the association of which is controlled by proteolysis of \u25b. Accordingly, the factors catalysing (ClpP, GroL) or preventing (DnaK) this proteolysis exert a crucial checkpoint of the assembly of Escherichia coli DNA polymerase III core

The emerging multiple roles of nuclear Akt.

Akt is a central player in the signal transduction pathways activated in response to many growth factors, hormones, cytokines, and nutrients and is thought to control a myriad of cellular functions including proliferation and survival, autophagy, metabolism, angiogenesis, motility, and exocytosis. Moreover, dysregulated Akt activity is being implicated in the pathogenesis of a growing number of disorders, including cancer. Evidence accumulated over the past 15 years has highlighted the presence of active Akt in the nucleus, where it acts as a fundamental component of key signaling pathways. For example, nuclear Akt counteracts apoptosis through a block of caspase-activated DNase: deoxyribonuclease and inhibition of chromatin condensation, and is also involved in cell cycle progression control, cell differentiation, mRNA: messenger RNA export, DNA repair, and tumorigenesis. In this review, we shall summarize the most relevant findings about nuclear Akt and its functions