The DNA Binding Properties of the Parsley bZIP Transcription Factor CPRF4a Are Regulated by Light

The common plant regulatory factors (CPRFs) from parsley are transcription factors with a basic leucine zipper motif that bind to cis-regulatory elements frequently found in promoters of light-regulated genes. Recent studies have revealed that certain CPRF proteins are regulated in response to light by changes in their expression level and in their intracellular localization. Here, we describe an additional mechanism contributing to the light-dependent regulation of CPRF proteins. We show that the DNA binding activity of the factor CPRF4a is modulated in a phosphorylation-dependent manner and that cytosolic components are involved in the regulation of this process. Moreover, we have identified a cytosolic kinase responsible for CPRF4a phosphorylation. Modification of recombinant CPRF4a by this kinase, however, is insufficient to cause a full activation of the factor, suggesting that additional modifications are required. Furthermore, we demonstrate that the DNA binding activity of the factor is modified upon light treatment. The results of additional irradiation experiments suggest that this photoresponse is controlled by different photoreceptor systems. We discuss the possible role of CPRF4a in light signal transduction as well as the emerging regulatory network controlling CPRF activities in parsley

Redundancy and specialization among plant microRNAs : role of the MIR164 family in developmental robustness

In plants, members of microRNA (miRNA) families are often predicted to target the same or overlapping sets of genes. It has thus been hypothesized that these miRNAs may act in a functionally redundant manner. This hypothesis is tested here by studying the effects of elimination of all three members of the MIR164 family from Arabidopsis. It was found that a loss of miR164 activity leads to a severe disruption of shoot development, in contrast to the effect of mutation in any single MIR164 gene. This indicates that these miRNAs are indeed functionally redundant. Differences in the expression patterns of the individual MIR164 genes imply, however, that redundancy among them is not complete, and that these miRNAs show functional specialization. Furthermore, the results of molecular and genetic analyses of miR164-mediated target regulation indicate that miR164 miRNAs function to control the transcript levels, as well as the expression patterns, of their targets, suggesting that they might contribute to developmental robustness. For two of the miR164 targets, namely CUP-SHAPED COTYLEDON1 (CUC1) and CUC2, we provide evidence for their involvement in the regulation of growth and show that their derepression in miR164 loss-of-function mutants is likely to account for most of the mutant phenotype

Genome-Wide Analysis of Gene Expression during Early Arabidopsis Flower Development

Detailed information about stage-specific changes in gene expression is crucial for the understanding of the gene regulatory networks underlying development. Here, we describe the global gene expression dynamics during early flower development, a key process in the life cycle of a plant, during which floral patterning and the specification of floral organs is established. We used a novel floral induction system in Arabidopsis, which allows the isolation of a large number of synchronized floral buds, in conjunction with whole-genome microarray analysis to identify genes with differential expression at distinct stages of flower development. We found that the onset of flower formation is characterized by a massive downregulation of genes in incipient floral primordia, which is followed by a predominance of gene activation during the differentiation of floral organs. Among the genes we identified as differentially expressed in the experiment, we detected a significant enrichment of closely related members of gene families. The expression profiles of these related genes were often highly correlated, indicating similar temporal expression patterns. Moreover, we found that the majority of these genes is specifically up-regulated during certain developmental stages. Because co-expressed members of gene families in Arabidopsis frequently act in a redundant manner, these results suggest a high degree of functional redundancy during early flower development, but also that its extent may vary in a stage-specific manner

Floral stem cell termination involves the direct regulation of AGAMOUS by PERIANTHIA

In Arabidopsis, the population of stem cells present in young flower buds is lost after the production of a fixed number of floral organs. The precisely timed repression of the stem cell identity gene WUSCHEL (WUS) by the floral homeotic protein AGAMOUS (AG) is a key part of this process. In this study, we report on the identification of a novel input into the process of floral stem cell regulation. We use genetics and chromatin immunoprecipitation assays to demonstrate that the bZIP transcription factor PERIANTHIA (PAN) plays a role in regulating stem cell fate by directly controlling AG expression and suggest that this activity is spatially restricted to the centermost region of the AG expression domain. These results suggest that the termination of floral stem cell fate is a multiply redundant process involving loci with unrelated floral patterning functions

Comunicación y emancipación. Reflexiones sobre el «giro lingüístico» de la Teoría Crítica

Noy availablePartiendo de las raíces hegelianas del pensamiento marxista, el autor intenta demostrar el reduccionismo implícito en el concepto marxiano de «praxis» con respecto a la dimensión simbólica de la acción humana, así como sus consecuencias epistemológicas y políticas. Como alternativa, defiende una reformulación de los supuestos básicos del materialismo histórico en términos teórico- comunicativos

Über Musik und Sprache: Variationen und Ergänzungen

In the first part of this essay, the relationship between music and language is discussed from two different points of view that simultaneously reveal two different dimensions of understanding music. Referring to Nelson Goodman, particularly to his term »metaphorical exemplification«, the possible meaning of a »language of music« is outlined. The »understanding« of this language is analogous to the (nonverbal) understanding of gestures, expressions, moods, atmospheres etc., and therefore akin to an understanding of meaning that does not require words. The understanding of musical art works, however, is not the understanding of a context of meaning (Sinnzusammenhang), since the means of creating musical coherence – such as repetition and variation, the game of identity and difference – are different from the means that create a context of meaning in verbal languages. Music’s affinity to language is at once music’s distance from language. The idea of understanding music must therefore be different from, or more than, the wordless understanding of gestural or expressive figures. Musical listening can rather be grasped as the re-enactment of an enigmatic interpenetration of sound, structure, and meaning, the understanding of which, among others, requires verbal explication. These forms of explication do not stand for a resolution of the enigma but, due to their interminability, sustain it. The second part of the essay demonstrates that the semiotic model of the understanding of music not only falls short due to its failure to accommodate musical coherence, but also because it blocks out areas of musical meaning that are only comprehensible structurally, and not necessarily amenable to wordless re-enactment. These areas include the crisis of the subject in new music (dating back to the late Beethoven), demonstrating a peculiar proximity between music and philosophy. This context connects music to a question of truth that not only refers to individual works, but also to the question of what art and music as an art form can mean today. One answer to this question, which has troubled modern art since the avant-garde movements of the early twentieth century, is suggested at the end of this essay in reference to Jacques Rancière: the tension between the autonomy of art and its dissolution of boundaries has become art’s condition of existence

Models of Freedom in the Contemporary World

Treba li pojam slobode tumačiti polazeći s točke gledišta pojedinca ili s točke gledišta zajednice? Ovisno o odgovoru na ovo pitanje mogu se razlikovati »individualističke« i »kolektivističke« ili »komunalističke« političke teorije. Premda se, prema shvaćanju autora teksta, dva navedena poimanja slobode uzajamno nadopunjuju — tekst razmatra njihovo suprotstavljanje u formi dileme radikalni individualizam ili radikalni komunalizam. Individualističke teorije, koje polaze od pojedinca kao izdvojenog i samostalnog, slobodu shvaćanja kao »negativnu« — omeđenu općim zakonom koji osigurava prava i slobode za svakoga. S druge strane, komunalističke teorije naglašavaju »normativni« karakter slobode, tematizujući specifičan način putem koga akteri unutar društva uopće dolaze do odluke što žele činiti. Smatrajući da su antropološke i epistemološke pretpostavke komunalizma, koji započinje sa Aristotelom, a u modernoj teoriji biva obnovljen od strane Hegela, dakako ispravnije od onih individualističke tradicije (Hobs, Kant, prosvetiteljstvo, romantizam, Nozik...), Wellmer razmatra način na koji se Hegelovi komunistički stavovi obnavljaju kod Marksa i Tokvila. Saglašavajući se sa Tokvilom da sferu »negativne slobode« i pozitivne opće slobode nije moguće jednoznačno razdvojiti, kao i sa stavom da sloboda može postojati tek kao oblik etičkog života odnosno komunalne prakse utjelotvorene u karakter, običaje i moralne osjećaje građana — autor ipak još jednom razmatra radikalnu dilemu individualizam/komunalizam inkarniranu u suprotstavljanju Habermasa i Nozieka. Razmatrajući odnos »negativne slobode«, »pozitivnih prava« i »opće volje« Wellmer utvrđuje da opredjeljivanje u sporu zavisi i od mogućnosti zasnivanja pojma komunalne ili diskurzivne racionalnosti — koja bi trebalo da zahvati normativnu strukturu »modernog konsenzusa« i pruži normativni sadržaj suvremenih koncepcija slobode. Nasuprot Habermasu, koji mu je inače blizak, Wellmer zaključuje da se Sloboda i Razum u savremenom svijetu ne podudaraju — unatoč tome što je zahtjevanje slobode racionalni zahtjev, a svrha negativne slobode: racionalna, komunalna sloboda.Should the concept of freedom be interpreted from the point of view of the community? Depending on the answer to this question one distinguishes »individualist« and »collectivist« or »communalist« political theories. Although, according to the author\u27s view, the two presented conceptions of freedom complement one another, in the text he analyses their opposition in the form of the dilemma: radical individualism or radical communalism. Individualist theories, which start off from the detached and independent individual, conceive freedom as »negative« — restricted by the universal law which ensures rights and freedom for everyone. On the other hand, communalist theories emphasize the »normative« character of freedom, thematizing the specific means used by the actors within a society, first of all, in reaching the decision concerning what they wish to do. Regarding the anthropological and episthemologica! presuppositions of communalism, originating with Aristotles, and in modem theory revived by Hegel, as certainly more proper than those of the individualist tradition (Hobbes, Kant, Enlightenment, Romanticism, Nozick...), Wellmer analyses how Hegel’s communalist views are revived in the works of Marx and Toqueville. Agreeing with Toqueville that the spheres of »negative freedom« and positive universal freedom cannot be unambiguously divided, as well as with the view that freedom can exist only as a form of ethical life, in other words, of communal practice embodied in the character, customs and moral feelings of citizens — the author, however, once again analyses the radical dilemma individualism/communalism incarnated in the opposition of Habermas towards Nozick. Considering the relation among »negative freedom«, »positive rights« and »universal will«, Wellmer establishes that commitment in the dispute depends also on the possibility of thinking out the concept of communal or discursive rationality — which should extend to the normative structure of the »modern consensus« and provide the normative content for contemporary concepts of freedom. In contrast to Habermas, to whom he is otherwise closely related in thought, Wellmer concludes that Freedom and Reason in the contemporary world do not correspond — despite the fact that the demand for freedom is a rational one, and that the aim of negative freedom is — rational, communal freedom