Targeting redox metabolism of the maize-Azospirillum brasilense interaction exposed to arsenic-affected groundwater.

Arsenic in groundwater constitutes an agronomic problem due to its potential accumulation in the food chain. Among the agro-sustainable tools to reduce metal(oid)s toxicity, the use of plant growth-promoting bacteria (PGPB) becomes important. For that, and based on previous results in which significant differences of As translocation were observed when inoculating maize plants with Az39 or CD Azospirillum strains, we decided to decipher the redox metabolism changes and the antioxidant system response of maize plants inoculated when exposed to a realistic arsenate (AsV ) dose. Results showed that AsV caused morphological changes in the root exodermis. Photosynthetic pigments decreased only in CD inoculated plants, while oxidative stress evidence was detected throughout the plant, regardless of the assayed strain. The antioxidant response was strain-differential since only CD inoculated plants showed an increase in superoxide dismutase, glutathione S-transferase (GST), and glutathione reductase (GR) activities while other enzymes showed the same behavior irrespective of the inoculated strain. Gene expression assays reported that only GST23 transcript level was upregulated by arsenate, regardless of the inoculated strain. AsV diminished the glutathione (GSH) content of roots inoculated with the Az39 strain, and CD inoculated plants showed a decrease of oxidized GSH (GSSG) levels. We suggest a model in which the antioxidant response of the maize-diazotrophs system is modulated by the strain and that GSH plays a central role acting mainly as a substrate for GST. These findings generate knowledge for a suitable PGPB selection, and its scaling to an effective bioinoculant formulation for maize crops exposed to adverse environmental conditions.

Cadmium induces two waves of reactive oxygen species in Glycine max (L.) roots.

Cadmium (Cd) is a non-essential heavy metal that may be toxic or even lethal to plants as it can be easily taken up by the roots and loaded into the xylem to the leaves. Using soybean roots (Glycine max L.) DM 4800, we have analysed various parameters related to reactive oxygen metabolism and nitric oxide (NO) during a 6 day Cd exposure. A rise in H(2)O(2) and NO, and to a lesser extent O(2)(·-) content was observed after 6 h exposure with a concomitant increase in lipid peroxidation and carbonyl group content. Both oxidative markers were significantly reduced after 24 h. A second, higher wave of O(2)(·-) production was also observed after 72 h of exposure followed by a reduction until the end of the treatment. NOX and glicolate oxidase activity might be involved in the initial Cd-induced reactive oxygen species (ROS) production and it appears that other sources may also participate. The analysis of antioxidative enzymes showed an increase in glutathione-S-transferase activity and in transcript levels and activity of enzymes involved in the ascorbate-glutathione cycle and the NADPH-generating enzymes. These results suggest that soybean is able to respond rapidly to oxidative stress imposed by Cd by improving the availability of NADPH necessary for the ascorbate-glutathione cycle.

Definition of the viral targets of protective HIV-1-specific T cell responses.

BACKGROUND: The efficacy of the CTL component of a future HIV-1 vaccine will depend on the induction of responses with the most potent antiviral activity and broad HLA class I restriction. However, current HIV vaccine designs are largely based on viral sequence alignments only, not incorporating experimental data on T cell function and specificity. METHODS: Here, 950 untreated HIV-1 clade B or -C infected individuals were tested for responses to sets of 410 overlapping peptides (OLP) spanning the entire HIV-1 proteome. For each OLP, a "protective ratio" (PR) was calculated as the ratio of median viral loads (VL) between OLP non-responders and responders. RESULTS: For both clades, there was a negative relationship between the PR and the entropy of the OLP sequence. There was also a significant additive effect of multiple responses to beneficial OLP. Responses to beneficial OLP were of significantly higher functional avidity than responses to non-beneficial OLP. They also had superior in-vitro antiviral activities and, importantly, were at least as predictive of individuals' viral loads than their HLA class I genotypes. CONCLUSIONS: The data thus identify immunogen sequence candidates for HIV and provide an approach for T cell immunogen design applicable to other viral infections.