8 research outputs found

    Heterologous expression of Pteris vittata ACR3 promotes arsenic tolerance but not accumulation in Arabidopsis

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    Arsenic is a class 1 carcinogen that causes widespread chronic human health issues due to the consumption of arsenic-contaminated groundwater and plant-based products. The Chinese brake fern Pteris vittata has the unique ability to hyperaccumulate arsenic to \u3e 1% dry weight in the fronds. In P. vittata gametophytes, the vacuolar protein ACR3 is necessary for arsenic tolerance and localizes to the tonoplast where it is thought to confer tolerance by effluxing arsenite from the cytoplasm into the vacuole for sequestration. ACR3 homologs are missing in angiosperms. When heterologously expressed in Arabidopsis thaliana, P. vittata ACR3 localizes to the plasma membrane and promotes arsenic tolerance, as measured by increased root length and shoot biomass on both As(III) and As(V) media compared to wild-type. Furthermore, transgenic lines expressing P. vittata ACR3 accumulate less arsenic in roots and shoots compared to wild-type plants. Reciprocally-grafted plants expressing ACR3 in the root only (but not those expressing ACR3 in the shoot only) show increased arsenic tolerance, suggesting that ACR3 acts primarily in the root to promote arsenic tolerance and decrease arsenic accumulation. Results suggest that heterologous P. vittata ACR3 expression confers the ability to efflux As(III) from the cytoplasm of Arabidopsis root cells, increasing arsenic tolerance and reducing accumulation in root and shoot tissues. These findings may have important implications for developing transgenic crops that accumulate less arsenic or for developing phytoremediation systems

    Differential expression of genes encoding phosphate transporters contributes to arsenic tolerance and accumulation in shrub willow (Salix spp.)

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    Studies of arsenate and phosphate uptake by plants in hydroponic and soil systems indicate a common transport mechanism via the phosphate transporters (PHTs) due to structural similarity of the anions. Typically, the presence of phosphate decreases plant uptake and translocation of arsenate in hydroponic solution. This study quantified arsenic (As) uptake related to the presence of phosphorus in an As-tolerant willow (Salix viminalis×. Salix miyabeana) and an As-sensitive willow (Salix eriocephala). Addition of phosphate resulted in greater As accumulation than in treatments without phosphate in both genotypes, although the tolerant genotype accumulated more As than the sensitive one. Expression of genes for two putative high-affinity phosphate transporters, PHT1;3 and PHT1;12, were up-regulated in both willow genotypes upon addition of As, but to a greater extent in the As-sensitive genotype. Expression of a third putative transporter, PHT1;4, was greater in the As-sensitive genotype but was not up-regulated as a result of As addition in either genotype. Leaves of the As-tolerant willow genotype contained greater concentrations of γ-glutamylcysteine (γEC) than the sensitive genotype, although this was not due to differential expression of the γ-glutamylcysteine synthetase (γECS) gene. The results suggest that increased expression of PHT1 upon exposure to As in an As-sensitive genotype contributes to rapid toxicity. Our data suggest that although detoxification capacity may be different between genotypes, the differences are not due to up-regulation of γECS or phytochelatin synthase. © 2011 Elsevier B.V

    Behavioral phenotypes of pediatric temporal lobe epilepsy

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    Objective: A broad spectrum of emotional-behavioral problems have been reported in pediatric temporal lobe epilepsy (TLE), but with considerable variability in their presence and nature of expression, which hampers precise identification and treatment. The present study aimed to empirically identify latent patterns or behavioral phenotypes and their correlates. Methods: Data included parental ratings of emotional-behavioral status on the Behavior Assessment System for Children, 2nd Edition (BASC-2) of 81 children (mean age = 11.79, standard deviation [SD] = 3.93) with TLE. The nine clinical subscales were subjected to unsupervised machine learning to identify behavioral subgroups. To explore concurrent validity and the underlying composition of the identified clusters, we examined demographic factors, seizure characteristics, psychosocial factors, neuropsychological performance, psychiatric status, and health-related quality of life (HRQoL). Results: Three behavioral phenotypes were identified, which included no behavioral concerns (Cluster 1, 43% of sample), externalizing problems (Cluster 2, 41% of sample), and internalizing problems (Cluster 3, 16% of sample). Behavioral phenotypes were characterized by important differences across clinical seizure variables, psychosocial/familial factors, everyday executive functioning, and HRQoL. Cluster 2 was associated with younger child age, lower maternal education, and higher rate of single-parent households. Cluster 3 was associated with older age at epilepsy onset and higher rates of hippocampal sclerosis and parental psychiatric history. Both Cluster 2 and 3 demonstrated elevated family stress. Concurrent validity was demonstrated through the association of psychiatric (i.e., rate of Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) disorders and psychotropic medication) and parent-rated HRQoL variables. Significance: Youth with TLE present with three distinct behavioral phenotypes that correspond with important clinical and sociodemographic markers. The current findings demonstrate the variability of behavioral presentations in youth with TLE and provide a preliminary framework for screening and targeting intervention to enhance support for youth with TLE and their families

    Adult plant resistance in maize to northern leaf spot is a feature of partial loss-of-function alleles of Hm1.

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    Adult plant resistance (APR) is an enigmatic phenomenon in which resistance genes are ineffective in protecting seedlings from disease but confer robust resistance at maturity. Maize has multiple cases in which genes confer APR to northern leaf spot, a lethal disease caused by Cochliobolus carbonum race 1 (CCR1). The first identified case of APR in maize is encoded by a hypomorphic allele, Hm1A, at the hm1 locus. In contrast, wild-type alleles of hm1 provide complete protection at all developmental stages and in every part of the maize plant. Hm1 encodes an NADPH-dependent reductase, which inactivates HC-toxin, a key virulence effector of CCR1. Cloning and characterization of Hm1A ruled out differential transcription or translation for its APR phenotype and identified an amino acid substitution that reduced HC-toxin reductase (HCTR) activity. The possibility of a causal relationship between the weak nature of Hm1A and its APR phenotype was confirmed by the generation of two new APR alleles of Hm1 by mutagenesis. The HCTRs encoded by these new APR alleles had undergone relatively conservative missense changes that partially reduced their enzymatic activity similar to HM1A. No difference in accumulation of HCTR was observed between adult and juvenile plants, suggesting that the susceptibility of seedlings derives from a greater need for HCTR activity, not reduced accumulation of the gene product. Conditions and treatments that altered the photosynthetic output of the host had a dramatic effect on resistance imparted by the APR alleles, demonstrating a link between the energetic or metabolic status of the host and disease resistance affected by HC-toxin catabolism by the APR alleles of HCTR
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