Buona fede e art. 41 Cost.: alla ricerca di un diritto contrattuale "giusto"

Tale contributo tenta di analizzare la problematica della libertà di iniziativa economica privata come limite e fondamento della libertà contrattuale dei privati concentrando l’attenzione sul rapporto contratto-giudice-mercato

Redox regulation of PEP activity during seedling establishment in Arabidopsis thaliana

Activation of the plastid-encoded RNA polymerase is tightly controlled and involves a network of phosphorylation and, as yet unidentified, thiol-mediated events. Here, we characterize PLASTID REDOX INSENSITIVE2, a redox-regulated protein required for full PEP-driven transcription. PRIN2 dimers can be reduced into the active monomeric form by thioredoxins through reduction of a disulfide bond. Exposure to light increases the ratio between the monomeric and dimeric forms of PRIN2. Complementation of prin2-2 with different PRIN2 protein variants demonstrates that the monomer is required for light-activated PEP-dependent transcription and that expression of the nuclear-encoded photosynthesis genes is linked to the activity of PEP. Activation of PEP during chloroplast development likely is the source of a retrograde signal that promotes nuclear LHCB expression. Thus, regulation of PRIN2 is the thiol-mediated mechanism required for full PEP activity, with PRIN2 monomerization via reduction by TRXs providing a mechanistic link between photosynthetic electron transport and activation of photosynthetic gene expression.</p

Role of poplar DNA demethylases in controlling winter dormancy

Trees have developed the mechanism of winter dormancy to survive the harsh conditions of winter in temperate and cold regions. It determines the geographical distribution of tree species and the long of the growing period. Epigenetic control of winter dormancy in woody plants is barely known. 5-methyl cytosine (5mC) is an important epigenetic mark that regulates gene expression in animals and plants. The profile of DNA methylation changes in the transition of developmental stages in plants such as chestnut bud set and burst, flowering in azalea, aging in pine trees among other. So far, the enzymes involved in the modification of the methylome and the molecular mechanism behind the control over those development processes remain to be understood. Our previous results showed higher DNA methylation and less acetylated Lys 8 of histone H4 global levels in poplar stem during winter dormancy compared to active growing season. Analysis of the 5-methyl cytosine levels by the application of the immunofluorescence-based method set up in our lab showed that global DNA methylation decrease significantly when trees are near to restore the growing season after the winter dormancy. We have identified two poplar homologs to Arabidopsis DME gene: PtaDML8/PtaDML10. DME protein promotes global DNA demethylation along the genome during the endosperm development. Our RT-PCR analyses indicate that the expression of PtaDML8/PtaDML10 genes increases significantly when trees are near to restart growing after the winter. Functional characterization showed that PtaDML8/PtaDML10 knockdown plants have a delayed in resuming of growth after dormancy. Taken together, we hypothesize that an active control of the 5mC DNA methylation play a key role in winter dormancy and that 5mC demethylases would be crucial for poplar dormant-growth transitio

Identificación y caracterización funcional del complejo nuclear de proteínas LSM de "Arabidopsis thaliana" en la respuesta de aclimatación a las temperaturas bajas

236 p.-35 fig.6 tab.El artículo adjunto contiene 9 fig. y 10 fig. supl.La numeración de las páginas del índice no se corresponde con el contenido. Hubo que cambiar el pdf de editor por el postprint por derechos de autor.Ver el mismo en: https://digital.csic.es/handle/10261/101232Living organisms are exposed to changes in their environment that can affect their development and reproduction. Plants, as sessile organisms, have developed mechanisms to cope with unfavorable environmental alterations. Low temperatures are among the factors that constraint their geographical distribution and can cause great economic losses. Species from temperate regions have evolved an adaptive response, named cold acclimation, so they can increase their constitutive freezing tolerance after exposure to low, nonfreezing temperatures (Levitt, 1980). Cold acclimation is a complex process during which many molecular and physiological changes take place, such as alterations in lipid composition, and increase in cytosolic calcium, abscisic acid (ABA), sugars and other osmolytes, among others (Salinas, 2002; Theocharis y col., 2012). In a general and simply way, the adaptive process begins with the sensing of low temperature by unknown receptors that transmit the signal inside the cell (Knight y Knight, 2012). In the cytoplasm, the signal is transduced and activates transcriptional factors that control gene expression (Huang y col., 2012). The coldregulated gene products, in a direct or indirect way, control the physiological changes that allow plants to increase freezing tolerance (Theocharis y col., 2012). Changes in gene expression are one of the mayor alterations that take place during cold acclimation, and much research has been conducted to elucidate how they are controled. Although coldregulated gene expression is tightly regulated at the transcriptional level, recent works have revealed that it is also under post-transcriptional, translational and post-translational control (Viswanathan y Zhu, 2002; Barrero-Gil y Salinas, 2013). The SM-LIKE (LSM) proteins constitute a large family of proteins involved in multiple aspects of RNA metabolism. In humans and yeast, there are eight highly conserved LSM proteins (LSM1 to LSM8) that form two different heptameric ring complexes, LSM1- LSM7 and LSM2-LSM8, localized in the cytoplasm and nucleus, respectively. LSM1 and LSM8 define and confer specificity to each complex, while the other LSM proteins (LSM2 to LSM7) participates in both cytoplasmic and nuclear complexes (Beggs, 2005). The LSM1-LSM7 cytoplasmic complex binds to oligoadenilated mRNAs, promoting their degradation. The LSM2-LSM8 nuclear complex binds to and stabilizes the U6 small nuclear RNA (U6 snRNA) in order to build the U6 small nuclear ribonucleoprotein (U6snRNP) and the core of the spliceosome, and functions in pre-mRNA splicing (Beggs, 2005). In silico studies identified potential homologs for all the LSM proteins in Arabidopsis, three of them being duplicated (LSM1, LSM3 and LSM6) (Wang y Brendel, 2004). To date, however, plant LSMs have nor been functionally characterized, and their role in RNA metabolism remains to be elucidated. Only Arabidopsis LSM5 and LSM4 genes have been experimentally studied, both of them being related to abscisic acid and osmotic stress signaling (Xiong y col., 2001b; Zhang y col., 2011). Previous work in our laboratory isolated a novel cold-inducible gene, RCI6, encoding a yeast and human LSM2 homolog. Besides RCI6/LSM2, all Arabidopsis LSM genes are coldinducible suggesting a function of LSM complexes in the regulation of cold acclimation in Arabidopsis. Therefore, the main objetives of this work were: • The functional characterization of Arabidopsis LSM2-LSM8 complex • The elucidation of the role of Arabidopsis LSM2-LSM8 complex in cold acclimationPeer reviewe

GOLDEN2‐LIKE transcription factors:A golden ticket to improve crops?

Societal impact statement: The human population is expected to reach 9.7 billion in the next 30 years, increasing the strain on our already precarious food system. Climate change is shifting weather patterns, leading to unpredictable and catastrophic events that further threaten the agronomic sector. Plant scientists are implementing biotechnological tools to sustainably increase both the production and nutritional content of our crops. Engineering GOLDEN2‐LIKE (GLK) transcription factors is a promising route to improve photosynthesis, as well as other important agronomical traits, to achieve food security for a growing population under an unpredictable climate. Summary: Using agricultural biotechnology to increase the photosynthetic efficiency of crops has been a focus of plant science research over the last two decades. Transcription factors coordinate the expression of gene networks that are the basis of plant development and physiological responses and, as such, are good targets to help improve photosynthesis. Among the known plant transcriptional regulators, GOLDEN2‐LIKE transcription factors (GLKs) may be ideal candidates to improve photosynthesis in crops, as they are master regulators of genes associated with photosynthesis and chloroplast biogenesis across a broad diversity of plant lineages. Moreover, recent work has revealed their involvement in environmental response, pathogen defence and development regulation across the plant's whole life cycle. Thus, manipulating GLK expression and activity, alone or likely in combination with other modifications, has clear potential to improve plant development and growth. Here, we review the research into GLK function and discuss the potential of these key transcription factors as biotechnological tools to enhance photosynthetic efficiency and stress tolerance in crops. Additionally, we take advantage of the vast plant genome and transcriptome datasets available to explore the evolutionary history of GLKs across the plant kingdom and discuss the implications for their adoption into crop engineering projects

Emerging from the darkness:interplay between light and plastid signaling during chloroplast biogenesis

Chloroplast biogenesis is a highly complex process that requires carefully coordinated communication between the nucleus and the chloroplast to integrate light signaling and information about the state of the plastid through retrograde signals. Most studies on plastid development have been performed using dark-grown seedlings and have focused on the transition from etioplast to chloroplast in response to light. Some advances are now also being made to understand the transition directly from proplastids to chloroplasts as it occurs in the shoot apical meristems. Recent reports have highlighted the importance of repressive mechanisms to block premature chloroplast development in dark, both at the transcriptional and post-transcriptional level. A group of new proteins with dual plastid and nuclear localization were shown to take part in the light triggered degradation of PHYTOCHROME INTERACTING FACTORs (PIFs) in the nucleus and thereby release the suppression of the nuclear photosynthesis associated genes. These dually localized proteins are also required to activate transcription of photosynthesis genes in the plastid in response to light, emphasizing the close link between the nucleus and the plastids during early light response. Furthermore, development of a fully functional chloroplast requires a plastid signal but the nature of this signal(s) is still unknown. GENOMES UNCOUPLED1 (GUN1) is a plastid protein pivotal for retrograde signal(s) during early seedling development, and recent reports have revealed multiple interactors of GUN1 from different plastid processes. These new GUN1 interactors could reveal the true molecular function of the enigmatic character, GUN1, under naturally occurring adverse growth conditions

LSM proteins provide accurate splicing and decay of selected transcripts to ensure normal arabidopsis development

57 p.-9 fig.-10 fig. supl. Este artículo forma parte de la tesis de Tamara Hernández-Verdeja, que se puede consultar en : http://digital.csic.es/handle/10261/109043In yeast and animals, Sm-like (LSM) proteins typically exist as heptameric complexes and are involved in different aspects of RNA metabolism. Eight LSM proteins, LSM1-8, are highly conserved and form two distinct heteroheptameric complexes, LSM1-7 and LSM2-8, that function in mRNA decay and splicing, respectively. A search of the Arabidopsis thaliana genome identifies eleven genes encoding proteins related to the eight conserved LSMs, the genes encoding the putative LSM1, LSM3 and LSM6 proteins being duplicated. Here, we report the molecular and functional characterization of the Arabidopsis LSM gene family. Our results show that the eleven LSM genes are active and encode proteins that are also organized in two different heptameric complexes. The complex LSM1-7 is cytoplasmic and is involved in P-body formation and mRNA decay by promoting decapping. The complex LSM2-8 is nuclear and is required for pre-mRNA splicing through U6 snRNA stabilization. More important, our results also reveal that these complexes are essential for the correct turnover and splicing of selected developmental-related mRNAs, and for the normal development of Arabidopsis. We propose that LSMs play a critical role in Arabidopsis development by ensuring the appropriate developmental-related gene expression through the control of mRNA splicing and decay.This work was supported by grants CSD2007-00057, EUI2009-04074 and BIO2010- 17545 from the Spanish Secretary of Research, Development and Innovation.Peer reviewe