Root cone angle is enlarged in docs1 LRR-RLK mutants in rice.

BACKGROUND: The DEFECTIVE IN OUTER CELL LAYER SPECIFICATION 1 (DOCS1) gene belongs to the Leucine-Rich Repeat Receptor-Like Kinase (LRR-RLK) subfamily. It has been discovered few years ago in Oryza sativa (rice) in a screen to isolate mutants with defects in sensitivity to aluminum. The c68 (docs1-1) mutant possessed a nonsense mutation in the C-terminal part of the DOCS1 kinase domain. FINDINGS: We have generated a new loss-of-function mutation in the DOCS1 gene (docs1-2) using the CRISPR-Cas9 technology. This new loss-of-function mutant and docs1-1 present similar phenotypes suggesting the original docs1-1 was a null allele. Besides the aluminum sensitivity phenotype, both docs1 mutants shared also several root phenotypes described previously: less root hairs and mixed identities of the outer cell layers. Moreover, our new results suggest that DOCS1 could also play a role in root cap development. We hypothesized these docs1 root phenotypes may affect gravity responses. As expected, in seedlings, the early gravitropic response was delayed. Furthermore, at adult stage, the root gravitropic set angle of docs1 mutants was also affected since docs1 mutant plants displayed larger root cone angles. CONCLUSIONS: All these observations add new insights into the DOCS1 gene function in gravitropic responses at several stages of plant development.

SHR overexpression induces the formation of supernumerary cell layers with cortex cell identity in rice.

The number of root cortex cell layers varies among plants, and many species have several cortical cell layers. We recently demonstrated that the two rice orthologs of the Arabidopsis SHR gene, OsSHR1 and OsSHR2, could complement the A. thaliana shr mutant. Moreover, OsSHR1 and OsSHR2 expression in A. thaliana roots induced the formation of extra root cortical cell layers. In this article, we demonstrate that the overexpression of AtSHR and OsSHR2 in rice roots leads to plants with wide and short roots that contain a high number of extra cortical cell layers. We hypothesize that SHR genes share a conserved function in the control of cortical cell layer division and the number of ground tissue cell layers in land plants.

Multiple mechanisms of nitrate sensing by Arabidopsis nitrate transceptor NRT1.1.

In Arabidopsis the plasma membrane nitrate transceptor (transporter/receptor) NRT1.1 governs many physiological and developmental responses to nitrate. Alongside facilitating nitrate uptake, NRT1.1 regulates the expression levels of many nitrate assimilation pathway genes, modulates root system architecture, relieves seed dormancy and protects plants from ammonium toxicity. Here, we assess the functional and phenotypic consequences of point mutations in two key residues of NRT1.1 (P492 and T101). We show that the point mutations differentially affect several of the NRT1.1-dependent responses to nitrate, namely the repression of lateral root development at low nitrate concentrations, and the short-term upregulation of the nitrate-uptake gene NRT2.1, and its longer-term downregulation, at high nitrate concentrations. We also show that these mutations have differential effects on genome-wide gene expression. Our findings indicate that NRT1.1 activates four separate signalling mechanisms, which have independent structural bases in the protein. In particular, we present evidence to suggest that the phosphorylated and non-phosphorylated forms of NRT1.1 at T101 have distinct signalling functions, and that the nitrate-dependent regulation of root development depends on the phosphorylated form. Our findings add to the evidence that NRT1.1 is able to trigger independent signalling pathways in Arabidopsis in response to different environmental conditions.

Highly efficient production and characterization of T-DNA plants for rice ( Oryza sativa L.) functional genomics.

We investigated the potential of an improved Agrobacterium tumefaciens-mediated transformation procedure of japonica rice ( Oryza sativa L.) for generating large numbers of T-DNA plants that are required for functional analysis of this model genome. Using a T-DNA construct bearing the hygromycin resistance ( hpt), green fluorescent protein ( gfp) and beta-glucuronidase ( gusA) genes, each individually driven by a CaMV 35S promoter, we established a highly efficient seed-embryo callus transformation procedure that results both in a high frequency (75-95%) of co-cultured calli yielding resistant cell lines and the generation of multiple (10 to more than 20) resistant cell lines per co-cultured callus. Efficiencies ranged from four to ten independent transformants per co-cultivated callus in various japonica cultivars. We further analysed the T-DNA integration patterns within a population of more than 200 transgenic plants. In the three cultivars studied, 30-40% of the T(0) plants were found to have integrated a single T-DNA copy. Analyses of segregation for hygromycin resistance in T(1) progenies showed that 30-50% of the lines harbouring multiple T-DNA insertions exhibited hpt gene silencing, whereas only 10% of lines harbouring a single T-DNA insertion was prone to silencing. Most of the lines silenced for hpt also exhibited apparent silencing of the gus and gfp genes borne by the T-DNA. The genomic regions flanking the left border of T-DNA insertion points were recovered in 477 plants and sequenced. Adapter-ligation Polymerase chain reaction analysis proved to be an efficient and reliable method to identify these sequences. By homology search, 77 T-DNA insertion sites were localized on BAC/PAC rice Nipponbare sequences. The influence of the organization of T-DNA integration on subsequent identification of T-DNA insertion sites and gene expression detection systems is discussed.

Efficient microprojectile bombardment-mediated transformation of rice using gene cassettes.

This study was aimed at determining whether gene cassettes (promoter-coding sequence-terminator) can be efficiently used in microprojectile acceleration-mediated co-transformation of rice in the place of whole plasmids, and to what extent their use influences the integration and expression of the co-transferred gene of interest. Two non-linked marker genes ( yfp and hph) were co-introduced by microprojectile bombardment into cells of embryogenic calli in three separate experiments. Three different DNA structures were compared for their ability to transiently and stably transform rice cells: supercoiled or linearized whole-plasmid DNA, gene cassette DNA and single-stranded gene cassette DNA coated with Escherichia coli single-stranded binding (SSB) proteins. Our results demonstrate that microprojectile bombardment-mediated transformation of rice using gene cassettes is possible without significantly reducing transformation efficiency in comparison to the use of whole-plasmid DNA. Furthermore, no obvious difference in transgene integration pattern and inheritance was observed among plants transformed with gene cassettes compared to those transformed with the whole plasmid, except that concatemerization of molecules prior to integration was rarely observed in gene cassette transformants.

Expression of a Bacillus thuringiensis cry1B synthetic gene protects Mediterranean rice against the striped stem borer.

BACILLUS THURINGIENSIS: Cry1Ba endotoxin, which was shown to exhibit a tenfold lower lethal concentration 50 (LC50) than Cry1Ac in a Striped Stem Borer (SSB) diet incorporation assay. The 1.950-bp synthetic cry1B gene, possessing an overall GC content of 58 %, was cloned under the control of the maize ubiquitin promoter first intron and first exon regions. The resulting vector, designated as pUbi-cry1B, was transferred to two commercial Mediterranean cultivars of rice, Ariete and Senia, using microprojectile acceleration-mediated transformation. Thirty-two and 47 T0 events were generated in cvs. Ariete and Senia, respectively. Southern blot and immunoblot analyses allowed the identification of 7 Senia and 1 Ariete events harbouring both an intact gene cassette and expressing Cry1B at a level ranging from 0.01% to 0.4% of the total soluble proteins. Three Senia and 1 Ariete events were found to be protected against second instar SSB larvae in whole plant feeding assays, exhibiting 90-100% mortality 7 days after infestation. Spatial and temporal variation in transgene expression was further examined in resistant event 64 of cv. Ariete. Stable accumulation of Cry1B, representing 0.4% of the total soluble proteins, was observed over the T2 to T4 generations in leaf tissue 20, 40, 70 and 90 days after germination in both young and old leaves and in internodes. Ariete event 64 was found to be fully protected from attacks of third and fourth instar SSB larvae over subsequent generations.

[The microbial etiology of genital discharges in Nouakchott, Mauritania]. / Etiologie microbienne des écoulements génitaux à Nouakchott, Mauritanie.

The survey carried on 579 patients of both sexes, consulting for genital discharges (spontaneous or referred), showed that in 61.1% men cases, STD agents were isolated (Neisseria gonorrhoeae 51.5%) and 64.4% in women cases (Gardnerella vaginalis 24%, Candida albicans 20%. Trichomonas vaginalis 14%). 17% of Neisseria gonorrhoeae strains were penicillinase-producing (PPNG).

[Visceral leishmaniasis in Niger: six new parasitologically confirmed cases]. / La leishmaniose viscérale au Niger: six nouveaux cas confirmés parasitologiquement.

From January 1992 to January 1995, six cases of Kala-azar have been observed in young soldiers at Niamey, Niger. All the patients had spent some time at Tin-Galene, in Aïr mountains, Northern Niger where they had been apparently contaminated. One patient was also infected with Salmonella and an other with Mycobacterium, but none of the six was positive for HIV. The 6 cases have been confirmed by the presence of Leishmania in the sternum bone-marrow. Four patients recovered after a treatment with Glucantime; two died because the treatment was too late. In Niger, Kala-azar prevalence is probably much higher than estimated previously. So far all the cases described or suspected were in the Saharan mountains of Aïr. The strains have not been typed and it is not possible to state if it is L. infantum or L. donovani. The vector of the two species Ph. orientalis and Ph. alexandri are known to occur in the area.

[Seroepidemiology of toxoplasmosis in Niamey, Niger]. / Séro-épidémiologie de la toxoplasmose à Niamey, Niger.

A seroepidemiological survey of toxoplasmosis was carried out in Niamey, Niger, in 1992. Three hundred and seventy-one sera from 200 females and 171 males were tested by indirect immunofluorescence assay for IgG. Using a cut-off value of 12 UI, 67 sera (18%) were positive. In this group detection of specific IgM by ELISA with immunocapture revealed 8 positive sera (11.9%). Seroprevalence of specific IgG was not correlated with ethnic origin or sex but did increase with age from 6.9% in subjects under 5 years to 34.9% in subjects 50 years and over. These findings are comparable with those from previous studies in similar climates and confirm that the prevalence of toxoplasmosis is higher in humid coastal regions than dry desert areas.

Intrarectal Quinimax (an association of Cinchona alkaloids) for the treatment of Plasmodium falciparum malaria in children in Niger: efficacy and pharmacokinetics.

In an attempt to avoid the complications associated with intramuscular quinine administration, we assessed the intrarectal route. Sixty-six children aged from 2 to 10 years with Plasmodium falciparum malaria were included in the study, which took place in Niamey, Niger. Fifty-five children were given 20 mg/kg of the diluted injectable form of Quinimax (a quinine, quinidine, cinchonine, cinchonidine association) intrarectally. A further 11 children with malaria were treated with 12.5 mg/kg of the same Quinimax solution by the intramuscular route. All the children were treated twice a day for 3 d. Blood samples were drawn from 20 children (15 treated intrarectally and 5 intramuscularly) for a kinetic study. Both modes of administration were well tolerated. Mean fever clearance times (+/- standard errors) were 48.6 +/- 2.7 h and 35.9 +/- 2.2 h in the intrarectal and intramuscular groups, respectively (P = 0.05). Mean parasite clearance times (+/- standard errors) and mean times to achieve 50% reduction in parasitaemia (+/- standard errors) were similar after intrarectal (46.5 +/- 5.7 h and 7.8 +/- 0.9 h respectively) and intramuscular administration (27.4 +/- 3.6 h and 8.7 +/- 1.7 h, respectively). Tmax. after intrarectal administration (2.7 +/- 0.4 h) did not differ significantly from the value after intramuscular administration (1.1 +/- 0.6 h), but Cmax. and the area under the concentration-time curve from 0 to 48 h were lower (4.9 +/- 0.6 mg/L and 230.0 +/- 9.6 mg/L.h, respectively) than after intramuscular administration (9.1 +/- 1.2 mg/L and 356.0 +/- 4.2 mg/L.h, respectively) (P < 0.001). Compared to the intramuscular route, intrarectal Quinimax bioavailability was 40%.(ABSTRACT TRUNCATED AT 250 WORDS)

[Rectal quinine, an alternative to parenteral injections for the treatment of childhood malaria. Clinical, parasitological and pharmacological study]. / La quinine intrarectale, une alternative aux injections parentérales pour le traitement du paludisme du jeune enfant. Etude clinique, parasitologique et pharmacologique.

In order to avoid the frequent side effects with injections of quinine in african children, empirical intrarectal administration of quinine (Quinimax, Sanofi Winthrop) has already been used successfully in Madagascar and Niger. In an attempt to optimise its use, a pharmacokinetic study was carried out with 66 children, 2 to 15 years old, admitted in pediatric unit for acute uncomplicated Plasmodium falciparum malaria, but warranting parenteral therapy. Children received Quinimax intrarectally (20 mg/kg/12h), intravenously (12,5 mg/kg in a slow infusion over 4 hours/12h) or intramusculary (12,5 mg/kg/12h). Plasma quinine concentrations were determined by HPLC. In this study, temperature and parasite clearance were similar in the 3 groups. A second randomized study was performed with 3 different dosages of intrarectal Quinimax: 8 and 13 mg/kg/8h and 20 mg/kg/12h. Temperature fell stably to normal at 36 hours with all regimens. Total clearance of parasitaemia was only obtained at 48 h with 30 mg/kg/12h regimen. Pharmacokinetic stimulation allowed to propose that intrarectal administration of Quinimax 20 mg/kg/8h would be a safe and effective regimen. A third approach studied the efficacy and pharmacokinetics of a new rectal quinine formulation (12,8 mg/kg/8h quinine gluconate) compared to IM and IV (8 mg/kg/8h) : at 36h, body temperature of all children was returned to normal and remained so until day 7. Parasitaemia expressed as a percentage of initial values was not different in the 3 groups after 48 h. At day 7, all the patients were aparasitaemics. The good tolerability and efficacy of this new intrarectal quinine formulation might allow to propose this route as an alternative to intramuscular route for the treatment of childhood malaria in Africa.

[The seroprevalence of human immunodeficiency virus infection (HIV) in the Touaregs and Peuls Bororo in Niger]. / Séroprévalence de l'infection par le virus de l'immunodéficience humaine (VIH) chez les Touaregs et Peuls Bororo au Niger.

A seroepidemiological study of endemic treponematosis (bejel) in Niger allows us to realise an anonymous non correlated screening of VIH infection in Nomads: Touaregs of Tchirozerine (Agadez), Peuls Boro of Bermo (Maradi). On the 424 Touaregs screened only one was seropositive to VIH2 infection confirmed with Western blot that means 0.23% of seroprevalency comparable to that 0.50% found in the general population. The seroprevalency of trepronematosis (VDRL + TPHA+) is 7% in the range of 5 to 15 years old (80%), period which corresponds to the transmission of Bejel. Moreover this population don't travel to the seaborder countries. Concerning the 213 of the Peuls Bororo screened we had only 3 undetermined reactions to Western blot 1 and 2, despite the high seroprevalence of the treponematosis (VDRL+ TPHA+): 22% mostly in the subjects of more than 15 years old (89.36%) which is the sexual intercourse and exodus period to the seaborder countries, where 66% of our VIH patients are infected.

Prevalence et antosensibilite des gonoccoques isoles a Niamey : analyse de 6.608 prelevements genitaux

Un bilan de la recherche de neisseria gonorrhoeae dans 6.608 prelevements genitaux effectues de 1985 a 1992; a Niamey est presente. Ce germe a ete isole 624 fois; soit une prevalence globale de 9;44 pour cent. Quant aux antibiogrammes; pour les 17 antibiotiques retenus; l'on constate de grandes variations dans la frequence de leur utilisation. Cela n'a pas permis de tirer des conclusions generalisables sur les taux d'efficacite de chacun de ces produits sur le gonocoque. Celui-ci semble cependant plus frequemment sensible au chloramphenicol; aux cyclines et a l'oleandomycine

[Evolution of the seroprevalence of HIV-1 and HIV-2 infections in the national hospital of Niamey, Niger]. / Evolution de la séroprévalence des infections à VIH1 et VIH2 à l'hôpital national de Niamey, Niger.

For 25,368 serologies examined in the biological laboratory of National Hospital of Niamey, Niger, from March 1987 to May 1990, the authors studied seroprevalence HIV1, HIV2 and HIV1 + HIV2 during this periode in the different groups studied: Blood donors, in women patients of child bearing age, pregnant women, prostitutes, prisoners and during systematic visits. It appears there is a tendancy of an increase in HIV1, a decrease in HIV2 and relative stability for the two profiles together.

[A clinical and serologic survey of bejel in north Burkina Faso]. / Enquête clinique et sérologique sur le béjel au nord du Burkina Faso.

A clinical and serological survey of endemic syphilis was carried out during March 1986 in a sahelian area of North Burkina Faso. Differences were found in the prevalence rate of clinical lesions and serological positivities between the children of different ethnic groups. For all the survey, 7.5% of the 5-14 years old children had clinical lesions and 22% had antibodies against Treponema. These rates were 3% and 41% among the adults. The results of this survey were strikingly near of those of a survey carried out 5 years before in the same area. Endemic syphilis appeared highly stable.