Explore the vast range of titles available.

Infection of crop species by parasitic plants is a major agricultural hindrance resulting in substantial crop losses worldwide. Parasitic plants establish vascular connections with the host plant via structures termed haustoria, which allow acquisition of water and nutrients, often to the detriment of the infected host. Despite the agricultural impact of parasitic plants, the molecular and developmental processes by which host/parasitic interactions are established are not well understood. Here, we examine the development and subsequent establishment of haustorial connections by the parasite dodder (Cuscuta pentagona) on tobacco (Nicotiana tabacum) plants. Formatin of haustoria in dodder is accompanied by upregulation of dodder KNOTTED-like homeobox transcription factors, including SHOOT MERISTEMLESS-like (STM). We demonstrate interspecific silencing of a STM gene in dodder driven by a vascular-specific promoter in transgenic host plants and find that this silencing disrupts dodder growth. The reduced efficacy of dodder infection on STM RNA interference transgenics results from defects in haustorial connection, development, and establishment. Identification of transgene-specific small RNAs in the parasite, coupled with reduced parasite fecundity and increased growth of the infected host, demonstrates the efficacy of interspecific small RNA—mediated silencing of parasite genes. This technology has the potential to be an effective method of biological control of plant parasite infection.

The activity of SHOOT MERISTEMLESS (STM) is required for the functioning of the shoot apical meristem (SAM). STM is expressed in the SAM but is down-regulated at the site of leaf initiation. STM is also required for the formation of compound leaves. However, how the activity of STM is regulated at the transcriptional, posttranscriptional, and posttranslational levels is poorly understood. We previously found two conserved noncoding sequences in the promoters of STM-like genes across angiosperms, the K-box and the RB-box. Here, we characterize the function of the RB-box in Arabidopsis (Arabidopsis thaliana). The RB-box, along with the K-box, regulates the expression of STM in leaf sinuses, which are areas on the leaf blade with meristematic potential. The RB-box also contributes to restrict STM expression to the SAM. We identified FAR1-RELATED SEQUENCES-RELATED FACTOR1 (FRF1) as a binding factor to the RB-box region. FRF1 is an uncharacterized member of a subfamily of four truncated proteins related to the FAR1-RELATED SEQUENCES factors. Internal deletion analysis of the STM promoter identified a region required to repress the expression of STM in hypocotyls. Expression of STM in leaf primordia under the control of the JAGGED promoter produced plants with partially undifferentiated leaves. We further found that the ELK domain has a role in the posttranslational regulation of STM by affecting the nuclear localization of STM.

Transcription factors (TFs) activate gene expression by binding to elements close to promoters or enhancers. Some TFs can bind to heterochromatic regions to initiate gene activation, suggesting that if a TF is able to bind to any type of heterochromatin, it can activate transcription. To investigate this possibility, we used the CRISPRa system based on dCas9-VPR as an artificial TF in Drosophila . dCas9-VPR was targeted to the TAHRE telomeric element, an example of constitutive heterochromatin, and to promoters and enhancers of the HOX Ultrabithorax ( Ubx ) and Sex Combs Reduced ( Scr ) genes in the context of facultative heterochromatin. dCas9-VPR robustly activated TAHRE transcription, showing that although this element is heterochromatic, dCas9-VPR was sufficient to activate its expression. In the case of HOX gene promoters, although Polycomb complexes epigenetically silence these genes, both were ectopically activated. When the artificial TF was directed to enhancers, we found that the expression pattern was different compared to the effect on the promoters. In the case of the Scr upstream enhancer, dCas9-VPR activated the gene ectopically but with less expressivity; however, ectopic activation also occurred in different cells. In the case of the bxI enhancer located in the third intron of Ubx , the presence of dCas9-VPR is capable of increasing transcription initiation while simultaneously blocking transcription elongation, generating a lack of functional phenotype. Our results show that CRISPRa system is able to activate transcription in any type of heterochromatin; nevertheless, its effect on transcription is subject to the intrinsic characteristics of each gene or regulatory element.

Background In the absence of an adequate prevention strategy, up to 20% of CMV IgG+ liver transplant recipients (LTR) will develop CMV disease. Despite improved reporting in CMV-DNAemia, there is no consensus as to what the ideal CMV-DNAemia cutoff for a successful preemptive strategy is. Each transplant centre establishes their own threshold. We aimed to determine the effectiveness of our preventive strategy in CMV IgG+ LTR, and evaluate CMV replication kinetics. Methods In this retrospective study we determined the incidence of CMV disease in the first 6 months following transplantation in CMV seropositive LTR in a tertiary-care centre in Mexico. Secondary outcomes were determining the number of patients who required preemptive therapy (treatment cutoff ≥ 4000 UI/ml), adherence to the centre’s prevention protocol and calculation of viral replication kinetics. Results One-hundred and twenty-four patients met inclusion criteria. Four patients (3.2%) developed CMV disease. Ninety-six (85%) had detectable DNAemia and 25 (22%) asymptomatic patients received preemptive therapy, none of them developed CMV disease. The highest viral loads were observed on the second posttransplant month. The number of viral load measurements decreased over time. Patients with DNAemia ≥ 4000 UI/ml had a faster viral load growth rate, shorter viral load duplication time, and higher basic reproductive number. Viral load growth rate and autoimmune hepatitis were associated with development of DNAemia ≥ 4000 UI/ml. Conclusion Cytomegalovirus disease occurred in 3.2% of the study subjects. Preemptive therapy using a threshold of CMV ≥ 4000 UI/ml was effective in reducing the incidence of end-organ disease. The viral replication parameters described in this population highlight the importance of frequent monitoring, a challenging feat for transplant programs in low- and middle-income countries.

A total of 13 individuals of the rodent Abrocoma bennetti were captured and 354 ectoparasites belonging to 14 different species were collected and analyzed. The most abundant species was the Phthiraptera Monogyropus longus (61.54%), followed by the Siphonaptera Neotyphloceras chilensis (38.46%). In this study Gyropus distinctus (15.38%) is reported as new record for A. bennetti, previously described for Octodon degus, a rodent usually living in sympatry with A. bennetti. For the first time the flea Delostichus smiti, and the mites Ornithonyssus sp. and Androlaelaps fahrenholzi are recorded in this rodent species.

Studies of host-parasite relationships largely benefit from adopting a multifactorial approach, including the complexity of multi-host systems and habitat features in their analyses. Some host species concentrate most infection and contribute disproportionately to parasite and vector population maintenance, and habitat feature variation creates important heterogeneity in host composition, influencing infection risk and the fate of disease dynamics. Here, we examine how the availability of specific groups of hosts and habitat features relate to vector abundance and infection risk in 18 vector populations along the Mediterranean-type ecosystem of South America, where the kissing bug Mepraia spinolai is the main wild vector of the parasite Trypanosoma cruzi , the etiological agent of Chagas disease. For each population, data on vectors, vertebrate host availability, vegetation, precipitation, and temperature were collected and analyzed. Vector abundance was positively related to temperature, total vegetation, and European rabbit availability. Infection risk was positively related to temperature, bromeliad cover, and reptile availability; and negatively to the total domestic mammal availability. The invasive rabbit is suggested as a key species involved in the vector population maintenance. Interestingly, lizard species –a group completely neglected as a potential reservoir–, temperature, and bromeliads were relevant factors accounting for infection risk variation across populations.

El presente artículo explora cómo un centro de aprendizaje efectivo sirve para impulsar el logro educativo, más allá de las condiciones socioeconómicas y características propias de los alumnos. Se empleó un modelo multinivel con resultados del Tercer Estudio Regional Comparativo y Explicativo (TERCE) para estudiantes ecuatorianos en lectura y matemáticas. Los resultados revelaron que entre 31 y 52% de la variación en los puntajes en estas pruebas se explican por las diferencias entre escuelas, reforzando así la importancia del efecto compensador de los centros educativos para equiparar las oportunidades de la población. This article examines how effective education institutions improve educational achievement, regardless of students’ socioeconomic backgrounds. The paper utilizes a multilevel model using data from the Third Regional Comparative and Explanatory Study (TERCE) for Ecuadorian students in reading and mathematics. Findings show that between 31 and 52% of the variation in test results is due to differences between schools, thus underlining the importance of the compensatory effect of schools in promoting equality of opportunity.

The activity ofSHOOT MERISTEMLESS (STM)is required for the functioning of the shoot apical meristem (SAM).STMis expressed n the SAM but is down-regulated at the site of leaf initiation.STMis also required for the formation of compound leaves. However, how the activity ofSTMis regulated at the transcriptional, posttranscriptional, and posttranslational levels is poorly understood.We previously found two conserved noncoding sequences in the promoters ofSTM-like genes across angiosperms, the K-box and the RB-box. Here, we characterize the function of the RB-box in Arabidopsis (Arabidopsis thaliana). The RB-box, along with the K-box, regulates the expression ofSTMin leaf sinuses, which are areas on the leaf blade with meristematic potential. The RB-box also contributes to restrictSTMexpression to the SAM. We identified FAR1-RELATED SEQUENCES-RELATED FACTOR1 (FRF1) as a binding factor to the RB-box region. FRF1 is an uncharacterized member of a subfamily of four truncated proteins related to the FAR1-RELATED SEQUENCES factors. Internal deletion analysis of theSTMpromoter identified a region required to repress the expression ofSTMin hypocotyls. Expression ofSTMin leaf primordia under the control of theJAGGEDpromoter produced plants with partially undifferentiated leaves.We further found that the ELK domain has a role in the posttranslational regulation of STM by affecting the nuclear localization of STM.

In order to analyse the effect of hosts’ relationships and the helminthic load on the switching of parasites between native and introduced hosts, we sampled rodents belonging to two suborders from Central Chile. We compared the number of helminthic species shared between murids (introduced) and cricetid (native, same suborder) rodents to those shared between murids and hystricomorphs (native, different suborder), and we assessed the association between parasitic presence, abundance and geographical dispersion in source hosts to the presence and abundance in recipient hosts. Introduced rodent species shared more helminth species with cricetid rodents than with non-cricetids. Presence and abundance in recipient hosts was not associated with the prevalence and mean abundance in source hosts’ population. The mean abundance of parasites in source hosts throughout the territory and wider dispersion was positively associated with the likelihood of being shared with a recipient host. Closer relationships between native and introduced hosts and high parasitic abundance and dispersion could facilitate host switching of helminths between native and introduced rodents. This work provides the first documentation of the importance of parasitic abundance and dispersion on the switching of parasites between native and introduced hosts.

The goal of this thesis was to investigate the domain-general predictors that underpin mathematics skills in early childhood. Thus, this thesis examined the role of working memory and language. In particular, the empirical work of this thesis focused on comparing how children do mathematics in a relatively pure context on the one hand, and in a more applied context on the other. Three studies were designed for this purpose. The first study investigated the contributions of working memory components to both arithmetic skills and applied mathematics in 5-to 6-year-olds. Study 1 showed, as expected, that the central executive plays an important role both in arithmetic skills and in applied mathematics. However, there was also an unexpected and somewhat surprising finding that also showed that both kinds of mathematics performance were significantly predicted by children's receptive vocabulary. Thus, the second study was designed to further investigate the specific contributions of receptive language skills in children's mathematics skills. Results from Study 2 were unexpected since the results obtained in Study 1 were not replicated. However, this was likely to be because the language measures had unexpectedly high executive functions components, and as such the language measures themselves were not transparent. Finally, the third study, although it did not followed directly from Study 1 and 2, it followed the subject of the role of language skills in pure and applied mathematics. Study 3 investigated the role of longitudinal linguistic precursors and concurrent language and executive functions in 4-year-old's mathematics skills. Results suggested that concurrent language skills were significant to both mathematics performance, and that inhibitory control was also contributing to applied mathematics. Collectively, these findings improve our understanding of the domain-general contributions underpinning mathematics in both pure and applied contexts.