Author
Fernando Ferreira
Other affiliations: Universidade Federal de Minas Gerais, Federal University of Bahia, University of Toronto ...read more
Bio: Fernando Ferreira is an academic researcher from University of São Paulo. The author has contributed to research in topics: Population & Herd. The author has an hindex of 40, co-authored 248 publications receiving 6713 citations. Previous affiliations of Fernando Ferreira include Universidade Federal de Minas Gerais & Federal University of Bahia.
Topics: Population, Herd, Seroprevalence, Medicine, Amblyomma cajennense
Papers published on a yearly basis
Papers
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TL;DR: The morphological phenotypes of some arr mutants suggest complex regulatory interactions and gene-specific functions among family members, suggesting a general involvement of type-A ARRs in light signal transduction.
Abstract: Type-A Arabidopsis (Arabidopsis thaliana) response regulators (ARRs) are a family of 10 genes that are rapidly induced by cytokinin and are highly similar to bacterial two-component response regulators. We have isolated T-DNA insertions in six of the type-A ARRs and constructed multiple insertional mutants, including the arr3,4,5,6,8,9 hextuple mutant. Single arr mutants were indistinguishable from the wild type in various cytokinin assays; double and higher order arr mutants showed progressively increasing sensitivity to cytokinin, indicating functional overlap among type-A ARRs and that these genes act as negative regulators of cytokinin responses. The induction of cytokinin primary response genes was amplified in arr mutants, indicating that the primary response to cytokinin is affected. Spatial patterns of ARR gene expression were consistent with partially redundant function of these genes in cytokinin signaling. The arr mutants show altered red light sensitivity, suggesting a general involvement of type-A ARRs in light signal transduction. Further, morphological phenotypes of some arr mutants suggest complex regulatory interactions and gene-specific functions among family members.
665 citations
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TL;DR: The evolutionarily ancient two-component system that is used by cytokinin branches to incorporate a unique family of plant-specific transcription factors is revealed.
Abstract: The plant hormone cytokinin regulates numerous growth and developmental processes. A signal transduction pathway for cytokinin has been elucidated that is similar to bacterial two-component phosphorelays. In Arabidopsis, this pathway is comprised of receptors that are similar to sensor histidine kinases, histidine-containing phosphotransfer proteins, and response regulators (ARRs). There are two classes of response regulators, the type-A ARRs, which act as negative regulators of cytokinin responses, and the type-B ARRs, which are transcription factors that play a positive role in mediating cytokinin-regulated gene expression. Here we show that several closely related members of the Arabidopsis AP2 gene family of unknown function are transcriptionally up-regulated by cytokinin through this pathway, and we have designated these AP2 genes CYTOKININ RESPONSE FACTORS (CRFs). In addition to their transcriptional regulation by cytokinin, the CRF proteins rapidly accumulate in the nucleus in response to cytokinin, and this relocalization depends on the histidine kinases and the downstream histidine-containing phosphotransfer proteins, but is independent of the ARRs. Analysis of loss-of-function mutations reveals that the CRFs function redundantly to regulate the development of embryos, cotyledons, and leaves. Furthermore, the CRFs mediate a large fraction of the transcriptional response to cytokinin, affecting a set of cytokinin-responsive genes that largely overlaps with type-B ARR targets. These results indicate that the CRF proteins function in tandem with the type-B ARRs to mediate the initial cytokinin response. Thus, the evolutionarily ancient two-component system that is used by cytokinin branches to incorporate a unique family of plant-specific transcription factors.
372 citations
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TL;DR: This review highlights the most recent advances in the understanding of cytokinin biosynthesis, metabolism and signalling and discusses how various environmental signals interact with these pathways to modulate plant growth, development and physiology.
Abstract: Cytokinins were discovered in the 1950s by their ability to promote cell division in cultured plant cells. Recently, there have been significant breakthroughs in our understanding of the biosynthesis, metabolism, perception and signal transduction of this phytohormone. These advances, coupled with physiological and other approaches, have enabled remarkable progress to be made in our understanding of the interactions between cytokinin function and environmental inputs. In this review, we first highlight the most recent advances in our understanding of cytokinin biosynthesis, metabolism and signalling. We then discuss how various environmental signals interact with these pathways to modulate plant growth, development and physiology.
348 citations
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TL;DR: Surveys of horse serum are a useful method of surveillance for Brazilian spotted fever in areas where humans are exposed to Amblyomma cajennense ticks.
Abstract: We compared the rickettsial infection status of Amblyomma cajennense ticks, humans, dogs, and horses in both Brazilian spotted fever (BSF)–endemic and –nonendemic areas in the state of Sao Paulo, Brazil Most of the horses and few dogs from BSF-endemic areas had serologic titers against Rickettsia rickettsii antigens In contrast, no dogs or horses from BSF-nonendemic areas had serologic titers against R rickettsii antigens, although they were continually exposed to A cajennense ticks All human serum samples and ticks from both areas were negative by serologic assay and polymerase chain reaction, respectively Our results indicate that surveys of horse serum are a useful method of BSF surveillance in areas where humans are exposed to A cajennense ticks In addition, we successfully performed experimental infection of A cajennense ticks with R parkeri
343 citations
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TL;DR: The results indicate that phosphorylation of the receiver domain is required for type-A ARR function and suggest that negative regulation of cytokinin signaling by the type-B ARRs most likely involves phosphorylated-dependent interactions, and show that a subset of the type of ARR proteins are stabilized in response to cytokinIn in part via phosphorylations.
Abstract: The plant hormone cytokinin regulates many aspects of growth and development. Cytokinin signaling involves His kinase receptors that perceive cytokinin and transmit the signal via a multistep phosphorelay similar to bacterial two-component signaling systems. The final targets of this phosphorelay are a set of Arabidopsis thaliana Response Regulator (ARR) proteins containing a receiver domain with a conserved Asp phosphorylation site. One class of these, the type-A ARRs, are negative regulators of cytokinin signaling that are rapidly transcriptionally upregulated in response to cytokinin. In this study, we tested the role of phosphorylation in type-A ARR function. Our results indicate that phosphorylation of the receiver domain is required for type-A ARR function and suggest that negative regulation of cytokinin signaling by the type-A ARRs most likely involves phosphorylation-dependent interactions. Furthermore, we show that a subset of the type-A ARR proteins are stabilized in response to cytokinin in part via phosphorylation. These studies shed light on the mechanism by which type-A ARRs act to negatively regulate cytokinin signaling and reveal a novel mechanism by which cytokinin controls type-A ARR function.
257 citations
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TL;DR: Recent advances are reported, updating current knowledge on classical defense hormones SA, JA, and ET, and the roles of auxin, abscisic acid (ABA), cytokinins (CKs), and brassinosteroids in molding plant-pathogen interactions are updated.
Abstract: Until recently, most studies on the role of hormones in plant-pathogen interactions focused on salicylic acid (SA), jasmonic acid (JA), and ethylene (ET). It is now clear that pathogen-induced modulation of signaling via other hormones contributes to virulence. A picture is emerging of complex crosstalk and induced hormonal changes that modulate disease and resistance, with outcomes dependent on pathogen lifestyles and the genetic constitution of the host. Recent progress has revealed intriguing similarities between hormone signaling mechanisms, with gene induction responses often achieved by derepression. Here, we report on recent advances, updating current knowledge on classical defense hormones SA, JA, and ET, and the roles of auxin, abscisic acid (ABA), cytokinins (CKs), and brassinosteroids in molding plant-pathogen interactions. We highlight an emerging theme that positive and negative regulators of these disparate hormone signaling pathways are crucial regulatory targets of hormonal crosstalk in disease and defense.
1,554 citations
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TL;DR: In this article, the authors analyze data on the sexual behavior of a random sample of individuals, and find that the cumulative distributions of the number of sexual partners during the twelve months prior to the survey decays as a power law with similar exponents for females and males.
Abstract: Many ``real-world'' networks are clearly defined while most ``social'' networks are to some extent subjective. Indeed, the accuracy of empirically-determined social networks is a question of some concern because individuals may have distinct perceptions of what constitutes a social link. One unambiguous type of connection is sexual contact. Here we analyze data on the sexual behavior of a random sample of individuals, and find that the cumulative distributions of the number of sexual partners during the twelve months prior to the survey decays as a power law with similar exponents $\alpha \approx 2.4$ for females and males. The scale-free nature of the web of human sexual contacts suggests that strategic interventions aimed at preventing the spread of sexually-transmitted diseases may be the most efficient approach.
1,476 citations
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TL;DR: The characterization of the molecular mechanisms regulating hormone synthesis, signaling, and action are facilitating the modification of hormone biosynthetic pathways for the generation of transgenic crop plants with enhanced abiotic stress tolerance.
1,106 citations
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TL;DR: The current knowledge on tick-borne rickettsiae and ricksettsioses is presented using a geographic approach toward the epidemiology of these diseases.
Abstract: Tick-borne rickettsioses are caused by obligate intracellular bacteria belonging to the spotted fever group of the genus Rickettsia. These zoonoses are among the oldest known vector-borne diseases. However, in the past 25 years, the scope and importance of the recognized tick-associated rickettsial pathogens have increased dramatically, making this complex of diseases an ideal paradigm for the understanding of emerging and reemerging infections. Several species of tick-borne rickettsiae that were considered nonpathogenic for decades are now associated with human infections, and novel Rickettsia species of undetermined pathogenicity continue to be detected in or isolated from ticks around the world. This remarkable expansion of information has been driven largely by the use of molecular techniques that have facilitated the identification of novel and previously recognized rickettsiae in ticks. New approaches, such as swabbing of eschars to obtain material to be tested by PCR, have emerged in recent years and have played a role in describing emerging tick-borne rickettsioses. Here, we present the current knowledge on tick-borne rickettsiae and rickettsioses using a geographic approach toward the epidemiology of these diseases.
1,016 citations
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TL;DR: The tick-borne rickettsioses described through 2005 are presented and the epidemiological circumstances that have played a role in the emergence of the newly recognized diseases are focused on.
Abstract: During most of the 20th century, the epidemiology of tick-borne rickettsioses could be summarized as the occurrence of a single pathogenic rickettsia on each continent. An element of this paradigm suggested that the many other characterized and noncharacterized rickettsiae isolated from ticks were not pathogenic to humans. In this context, it was considered that relatively few tick-borne rickettsiae caused human disease. This concept was modified extensively from 1984 through 2005 by the identification of at least 11 additional rickettsial species or subspecies that cause tick-borne rickettsioses around the world. Of these agents, seven were initially isolated from ticks, often years or decades before a definitive association with human disease was established. We present here the tick-borne rickettsioses described through 2005 and focus on the epidemiological circumstances that have played a role in the emergence of the newly recognized diseases.
989 citations