Unexpectedly low nitrogen acquisition and absence of root architecture adaptation to nitrate supply in a Medicago truncatula highly branched root mutant.

To complement N2 fixation through symbiosis, legumes can efficiently acquire soil mineral N through adapted root architecture. However, root architecture adaptation to mineral N availability has been little studied in legumes. Therefore, this study investigated the effect of nitrate availability on root architecture in Medicago truncatula and assessed the N-uptake potential of a new highly branched root mutant, TR185. The effects of varying nitrate supply on both root architecture and N uptake were characterized in the mutant and in the wild type. Surprisingly, the root architecture of the mutant was not modified by variation in nitrate supply. Moreover, despite its highly branched root architecture, TR185 had a permanently N-starved phenotype. A transcriptome analysis was performed to identify genes differentially expressed between the two genotypes. This analysis revealed differential responses related to the nitrate acquisition pathway and confirmed that N starvation occurred in TR185. Changes in amino acid content and expression of genes involved in the phenylpropanoid pathway were associated with differences in root architecture between the mutant and the wild type.

Application of the pulsed light technology to mycotoxin degradation and inactivation.

The persistence of mycotoxins and their metabolites in agricultural products is a major safety concern because of their high resistance to all kinds of decontamination techniques. In this study, we evaluated the effectiveness of the pulsed light technology for the degradation of mycotoxins. We report that eight flashes of pulsed light destroyed of 84.5 ± 1.9, 72.5 ± 1.1, 92.7 ± 0.8 and 98.1 ± 0.2% of zearalenone, deoxynivalenol, aflatoxin B1 and ochratoxin in solution. The degradation of the molecules was monitored by HPLC and LC-MS/MS analysis. We estimated the potential toxicity of zearalenone and deoxynivelenol after exposure to a pulsed light treatment using the Caenorhabditis elegans survival tests. The genotoxicity of aflatoxin B1 was also investigated using a complete Ames test. The results show that the treatment of zearalenone and deoxynivelenol by single or multiple flashes of pulsed light is associated with a stagnation or marginal decrease of the toxicity of the mycotoxins and that treatment of aflatoxin B1 by pulsed light can completely eliminate the mutagenic potential of this mycotoxin. This work provides the first demonstration of a nonthermal technology allowing mycotoxin destruction and inactivation of their mutagenic activity.