Histone 2B monoubiquitination complex integrates transcript elongation with RNA processing at circadian clock and flowering regulators

Altres ajuts: CERCA Programme/Generalitat de CatalunyaHISTONE MONOUBIQUITINATION1 (HUB1) and its paralog HUB2 act in a conserved heterotetrameric complex in the chromatin-mediated transcriptional modulation of developmental programs, such as flowering time, dormancy, and the circadian clock. The KHD1 and SPEN3 proteins were identified as interactors of the HUB1 and HUB2 proteins with in vitro RNA-binding activity. Mutants in SPEN3 and KHD1 had reduced rosette and leaf areas. Strikingly, in spen3 mutants, the flowering time was slightly, but significantly, delayed, as opposed to the early flowering time in the hub1-4 mutant. The mutant phenotypes in biomass and flowering time suggested a deregulation of their respective regulatory genes CIRCADIAN CLOCK-ASSOCIATED1 (CCA1) and FLOWERING LOCUS C (FLC) that are known targets of the HUB1-mediated histone H2B monoubiquitination (H2Bub). Indeed, in the spen3-1 and hub1-4 mutants, the circadian clock period was shortened as observed by luciferase reporter assays, the levels of the CCA1α and CCA1β splice forms were altered, and the CCA1 expression and H2Bub levels were reduced. In the spen3-1 mutant, the delay in flowering time was correlated with an enhanced FLC expression, possibly due to an increased distal versus proximal ratio of its antisense COOLAIR transcript. Together with transcriptomic and double-mutant analyses, our data revealed that the HUB1 interaction with SPEN3 links H2Bub during transcript elongation with pre-mRNA processing at CCA1. Furthermore, the presence of an intact HUB1 at the FLC is required for SPEN3 function in the formation of the FLC-derived antisense COOLAIR transcripts

The Evening Complex establishes repressive chromatin domains via H2A.Z deposition

The Evening Complex (EC) is a core component of the Arabidopsis (Arabidopsis thaliana) circadian clock, which represses target gene expression at the end of the day and integrates temperature information to coordinate environmental and endogenous signals. Here we show that the EC induces repressive chromatin structure to regulate the evening transcriptome. The EC component ELF3 directly interacts with a protein from the SWI2/SNF2-RELATED (SWR1) complex to control deposition of H2A.Z-nucleosomes at the EC target genes. SWR1 components display circadian oscillation in gene expression with a peak at dusk. In turn, SWR1 is required for the circadian clockwork, as defects in SWR1 activity alter morning55 expressed genes. The EC-SWR1 complex binds to the loci of the core clock genes PSEUDO56 RESPONSE REGULATOR7 (PRR7) and PRR9 and catalyzes deposition of nucleosomes containing the histone variant H2A.Z coincident with the repression of these genes at dusk. This provides a mechanism by which the circadian clock temporally establishes repressive chromatin domains to shape oscillatory gene expression around dusk

Fruit load modulates flowering-related gene expression in buds of alternate-bearing 'Moncada' mandarin

Background and Aims Gene determination of flowering is the result of complex interactions involving both promoters and inhibitors. In this study, the expression of flowering-related genes at the meristem level in alternate-bearing citrus trees is analysed, together with the interplay between buds and leaves in the determination of flowering. Methods First defruiting experiments were performed to manipulate blossoming intensity in `Moncada¿ mandarin, Citrus clementina. Further defoliation was performed to elucidate the role leaves play in the flowering process. In both cases, the activity of flowering-related genes was investigated at the flower induction (November) and differentiation (February) stages. Key Results Study of the expression pattern of flowering-genes in buds from on (fully loaded) and off (without fruits) trees revealed that homologues of FLOWERING LOCUS T (CiFT), TWIN SISTER OF FT (TSF), APETALA1 (CsAP1) and LEAFY (CsLFY) were negatively affected by fruit load. CiFT and TSF activities showed a marked increase in buds from off trees through the study period (ten-fold in November). By contrast, expression of the homologues of the flowering inhibitors of TERMINAL FLOWER 1 (CsTFL), TERMINAL FLOWER 2 (TFL2) and FLOWERING LOCUS C (FLC) was generally lower in off trees. Regarding floral identity genes, the increase in CsAP1 expression in off trees was much greater in buds than in leaves, and significant variations in CsLFY expression (approx. 20 %) were found only in February. Defoliation experiments further revealed that the absence of leaves completely abolished blossoming and severely affected the expression of most of the flowering-related genes, particularly decreasing the activity of floral promoters and of CsAP1 at the induction stage. Conclusions These results suggest that the presence of fruit affects flowering by greatly altering gene-expression not only at the leaf but also at the meristem level. Although leaves are required for flowering to occur, their absence strongly affects the activity of floral promoters and identity genes.This work was supported by a grant from the Instituto Nacional Investigaciones Agrarias, Spain (RTA2009-00147). M. C. Gonzalez was the recipient of a contract by the Fundacion Agroalimed (Conselleria d'Agricultura, Pesca i Alimentacio, Generalitat Valenciana).Muñoz Fambuena, N.; Mesejo Conejos, C.; Gonzalez Más, MC.; Primo-Millo, E.; Agustí Fonfría, M.; Iglesias, DJ. (2012). Fruit load modulates flowering-related gene expression in buds of alternate-bearing 'Moncada' mandarin. Annals of Botany. 110(6):1109-1118. doi:10.1093/aob/mcs190S110911181106Abe, M. (2005). FD, a bZIP Protein Mediating Signals from the Floral Pathway Integrator FT at the Shoot Apex. Science, 309(5737), 1052-1056. doi:10.1126/science.1115983Bustin, S. (2002). Quantification of mRNA using real-time reverse transcription PCR (RT-PCR): trends and problems. 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Balance or Synergies between Environment and Economy—A Note on Model Structures

The UN sustainable development goals contain environmental, economic, and social objectives. They may only be reached, or at least it would be easier to reach them, if instead of a trade-off between these objectives that implies a need for balancing them, there are synergies to be reaped. This paper discusses how the structures of economic models typically used in policy analysis influence whether win–win strategies for the environment and the economy can be conceptualised and analysed. With a focus on climate policy modelling, the paper points out how, by construction, commonly used model structures find mitigation costs rather than benefits. This paper describes mechanisms that, when added to these model structures, can bring win–win options into a model’s solution horizon, and which provide a spectrum of alternative modelling approaches that allow for the identification of such options

Service cost model and cost comparative studies

PurposeThe purpose of this paper is to propose a service cost model which can be used to evaluate the impact of different management functionalities or network platforms to the service cost.Design/methodology/approachFollowing the validation of the importance that OpEx has on the overall TCO, a classification of the costs is proposed, based on their relation to the network. Two main types of costs have been identified: network based costs and service based costs. Both cost types have been modeled as a set of interconnected processes based on the network and service life cycle respectively. Network and service cost models have been integrated into a single framework. These models have been implemented as Markov chains, which include the dynamic behavior of services. Two different methods for the implementation (analytical versus non‐analytical) have been compared from the implementation and computation time point of view. The proposed service model has been used in two case studies: cost comparison of different types of services on different platforms; and impact of the service type distribution on the overall service cost on different platforms.FindingsThis paper finds the utility that the proposed cost model has. It has been shown that the impact on the overall service cost that a particular network platform capability such as the possibility of establishing point to multipoint connections has.. The proposed network and service cost models can be used on different types of networks and services.Originality/valueThe paper presents a general service cost model that can be used to study the impact of any management functionality or network platform has on the service cost.</jats:sec