Production of low-Cs+ rice plants by inactivation of the K+ transporter OsHAK1 with the CRISPR-Cas system.

The occurrence of radiocesium in food has raised sharp health concerns after nuclear accidents. Despite being present at low concentrations in contaminated soils (below µm), cesium (Cs+ ) can be taken up by crops and transported to their edible parts. This plant capacity to take up Cs+ from low concentrations has notably affected the production of rice (Oryza sativa L.) in Japan after the nuclear accident at Fukushima in 2011. Several strategies have been put into practice to reduce Cs+ content in this crop species such as contaminated soil removal or adaptation of agricultural practices, including dedicated fertilizer management, with limited impact or pernicious side-effects. Conversely, the development of biotechnological approaches aimed at reducing Cs+ accumulation in rice remain challenging. Here, we show that inactivation of the Cs+ -permeable K+ transporter OsHAK1 with the CRISPR-Cas system dramatically reduced Cs+ uptake by rice plants. Cs+ uptake in rice roots and in transformed yeast cells that expressed OsHAK1 displayed very similar kinetics parameters. In rice, Cs+ uptake is dependent on two functional properties of OsHAK1: (i) a poor capacity of this system to discriminate between Cs+ and K+ ; and (ii) a high capacity to transport Cs+ from very low external concentrations that is likely to involve an active transport mechanism. In an experiment with a Fukushima soil highly contaminated with 137 Cs+ , plants lacking OsHAK1 function displayed strikingly reduced levels of 137 Cs+ in roots and shoots. These results open stimulating perspectives to smartly produce safe food in regions contaminated by nuclear accidents.

Constitutive Contribution by the Rice OsHKT1;4 Na+ Transporter to Xylem Sap Desalinization and Low Na+ Accumulation in Young Leaves Under Low as High External Na+ Conditions.

HKT Na+ transporters correspond to major salt tolerance QTLs in different plant species and are targets of great interest for breeders. In rice, the HKT family is composed of seven or eight functional genes depending on cultivars. Three rice HKT genes, OsHKT1;1, OsHKT1;4 and OsHKT1;5, are known to contribute to salt tolerance by reducing Na+ accumulation in shoots upon salt stress. Here, we further investigate the mechanisms by which OsHKT1;4 contributes to this process and extend this analysis to the role of this transporter in plants in presence of low Na+ concentrations. By analyzing transgenic rice plants expressing a GUS reporter gene construct, we observed that OsHKT1;4 is mainly expressed in xylem parenchyma in both roots and leaves. Using mutant lines expressing artificial microRNA that selectively reduced OsHKT1;4 expression, the involvement of OsHKT1;4 in retrieving Na+ from the xylem sap in the roots upon salt stress was evidenced. Since OsHKT1;4 was found to be also well expressed in the roots in absence of salt stress, we extended the analysis of its role when plants were subjected to non-toxic Na+ conditions (0.5 and 5 mM). Our finding that the transporter, expressed in Xenopus oocytes, displayed a relatively high affinity for Na+, just above 1 mM, provided first support to the hypothesis that OsHKT1;4 could have a physiological role at low Na+ concentrations. We observed that progressive desalinization of the xylem sap along its ascent to the leaf blades still occurred in plants grown at submillimolar Na+ concentration, and that OsHKT1;4 was involved in reducing xylem sap Na+ concentration in roots in these conditions too. Its contribution to tissue desalinization from roots to young mature leaf blades appeared to be rather similar in the whole range of explored external Na+ concentrations, from submillimolar to salt stress conditions. Our data therefore indicate that HKT transporters can be involved in controlling Na+ translocation from roots to shoots in a much wider range of Na+ concentrations than previously thought. This asks questions about the roles of such a transporter-mediated maintaining of tissue Na+ content gradients in non-toxic conditions.

Internal Cs+ inhibits root elongation in rice.

The root system anchors the plant to the soil and contributes to plant autotrophy by taking up nutrients and water. In relation with this nutritional function, root development is largely impacted by availability of nutrients and water. Due to human activity, plants, in particular crops, can also be exposed to pollutants which can be absorbed and incorporated into the food chain. Cesium in soils is present at non-toxic concentrations for the plant (micromolar or less), even in soils highly polluted with radioactive cesium due to nuclear accidents. Here, we report on the morphological response of rice roots to Cs+ at micromolar concentrations. It is shown that Cs+ reduces root elongation without affecting root dry weight. Noteworthy, inactivation of the Cs+-permeable K+ transporter OsHAK1 prevents such effect of Cs+, suggesting that internal Cs+ triggers the modification of the root system.

[Bacteriologic features of urinary tract infections in children in the Sousse area, Tunisia]. / Particularités bactériologiques des infections urinaires chez l'enfant dans la région de Sousse, Tunisie.

Urinary tract infection (UTI) is frequent in childhood. Our purpose is to determine the bacteriologic profile of UTI in children through a retrospective study of 1281 urinary specimens analysed in the Laboratory of Microbiology of F. Hached University hospital of Sousse between 1997 and 2002 (2000 except). The most frequent pathogens recovered were E. coli (71%), K. pneumoniae (10%) P. mirabilis (8%), Staphylococcus (1.6%), P. aeruginosa (1%) and others (2%). E. coli susceptibility to antibiotics was characterised by the high resistance percentage to amoxicillin (60%), to amoxicilline - acid clavulanic (54%) and to cotrimoxazole (40%). The resistance percentage to third generation cephalosporins, to aminoglycosides and to nitrofurane remained very low, respectively of 1.5%, 1% and 1%. High resistance rates among K. pneumoniae strains towards to amoxicillin - acid clavulanic and Cefotaxim, respectively of 63 and 39% were noticed. The resistance percentages to amikacin and cotrimoxazole were respectively of 17 and 65%, but only of 4% to nitrofurane. 70% of P. mirabilis strains were resistant to amoxicillin, 63% of them remained susceptible to amoxicillin - acid clavulanic. No resistance was shown to amikacin against 31% towards cotrimoxazole.

Citalopram treatment of minor depression in elderly men: an open pilot study.

Antidepressant pharmacotherapy in elderly patients is challenging. The authors examined the use of citalopram to treat late-life minor depression. Ten men (mean age: 73+/-2 years) with DSM-IV Minor Depression were administered citalopram 20 mg/day. Efficacy was measured with the Geriatric Depression Scale (GDS), the Montgomery-Asberg Depression Rating Scale (MADRS), and the Clinical Global Impressions of Severity (CGI-S) scales. Citalopram was well tolerated, and GDS, MADRS, and CGI-S scores decreased after 12 weeks. These findings indicate that citalopram is safe and effective in the treatment of late-life minor depression.