A gene regulatory network critical for axillary bud dormancy directly controlled by Arabidopsis BRANCHED1.

The Arabidopsis thaliana transcription factor BRANCHED1 (BRC1) plays a pivotal role in the control of shoot branching as it integrates environmental and endogenous signals that influence axillary bud growth. Despite its remarkable activity as a growth inhibitor, the mechanisms by which BRC1 promotes bud dormancy are largely unknown. We determined the genome-wide BRC1 binding sites in vivo and combined these with transcriptomic data and gene co-expression analyses to identify bona fide BRC1 direct targets. Next, we integrated multi-omics data to infer the BRC1 gene regulatory network (GRN) and used graph theory techniques to find network motifs that control the GRN dynamics. We generated an open online tool to interrogate this network. A group of BRC1 target genes encoding transcription factors (BTFs) orchestrate this intricate transcriptional network enriched in abscisic acid-related components. Promoter::ß-GLUCURONIDASE transgenic lines confirmed that BTFs are expressed in axillary buds. Transient co-expression assays and studies in planta using mutant lines validated the role of BTFs in modulating the GRN and promoting bud dormancy. This knowledge provides access to the developmental mechanisms that regulate shoot branching and helps identify candidate genes to use as tools to adapt plant architecture and crop production to ever-changing environmental conditions.

ALGAEFUN with MARACAS, microALGAE FUNctional enrichment tool for MicroAlgae RnA-seq and Chip-seq AnalysiS.

BACKGROUND: Microalgae are emerging as promising sustainable sources for biofuels, biostimulants in agriculture, soil bioremediation, feed and human nutrients. Nonetheless, the molecular mechanisms underpinning microalgae physiology and the biosynthesis of compounds of biotechnological interest are largely uncharacterized. This hinders the development of microalgae full potential as cell-factories. The recent application of omics technologies into microalgae research aims at unraveling these systems. Nevertheless, the lack of specific tools for analysing omics raw data generated from microalgae to provide biological meaningful information are hampering the impact of these technologies. The purpose of ALGAEFUN with MARACAS consists in providing researchers in microalgae with an enabling tool that will allow them to exploit transcriptomic and cistromic high-throughput sequencing data. RESULTS: ALGAEFUN with MARACAS consists of two different tools. First, MARACAS (MicroAlgae RnA-seq and Chip-seq AnalysiS) implements a fully automatic computational pipeline receiving as input RNA-seq (RNA sequencing) or ChIP-seq (chromatin immunoprecipitation sequencing) raw data from microalgae studies. MARACAS generates sets of differentially expressed genes or lists of genomic loci for RNA-seq and ChIP-seq analysis respectively. Second, ALGAEFUN (microALGAE FUNctional enrichment tool) is a web-based application where gene sets generated from RNA-seq analysis as well as lists of genomic loci from ChIP-seq analysis can be used as input. On the one hand, it can be used to perform Gene Ontology and biological pathways enrichment analysis over gene sets. On the other hand, using the results of ChIP-seq data analysis, it identifies a set of potential target genes and analyses the distribution of the loci over gene features. Graphical representation of the results as well as tables with gene annotations are generated and can be downloaded for further analysis. CONCLUSIONS: ALGAEFUN with MARACAS provides an integrated environment for the microalgae research community that facilitates the process of obtaining relevant biological information from raw RNA-seq and ChIP-seq data. These applications are designed to assist researchers in the interpretation of gene lists and genomic loci based on functional enrichment analysis. ALGAEFUN with MARACAS is publicly available on https://greennetwork.us.es/AlgaeFUN/ .

CONSTANS-FKBP12 interaction contributes to modulation of photoperiodic flowering in Arabidopsis.

Flowering time is a key process in plant development. Photoperiodic signals play a crucial role in the floral transition in Arabidopsis thaliana, and the protein CONSTANS (CO) has a central regulatory function that is tightly regulated at the transcriptional and post-translational levels. The stability of CO protein depends on a light-driven proteasome process that optimizes its accumulation in the evening to promote the production of the florigen FLOWERING LOCUS T (FT) and induce seasonal flowering. To further investigate the post-translational regulation of CO protein we have dissected its interactome network employing in vivo and in vitro assays and molecular genetics approaches. The immunophilin FKBP12 has been identified in Arabidopsis as a CO interactor that regulates its accumulation and activity. FKBP12 and CO interact through the CCT domain, affecting the stability and function of CO. fkbp12 insertion mutants show a delay in flowering time, while FKBP12 overexpression accelerates flowering, and these phenotypes can be directly related to a change in accumulation of FT protein. The interaction is conserved between the Chlamydomonas algal orthologs CrCO-CrFKBP12, revealing an ancient regulatory step in photoperiod regulation of plant development.

CONSTANS alters the circadian clock in Arabidopsis thaliana.

Plants are sessile organisms that have acquired highly plastic developmental strategies to adapt to the environment. Among these processes, the floral transition is essential to ensure reproductive success and is finely regulated by several internal and external genetic networks. The photoperiodic pathway, which controls plant response to day length, is one of the most important pathways controlling flowering. In Arabidopsis photoperiodic flowering, CONSTANS (CO) is the central gene activating the expression of the florigen FLOWERING LOCUS T (FT) in the leaves at the end of a long day. The circadian clock strongly regulates CO expression. However, to date, no evidence has been reported regarding a feedback loop from the photoperiod pathway back to the circadian clock. Using transcriptional networks, we have identified relevant network motifs regulating the interplay between the circadian clock and the photoperiod pathway. Gene expression, chromatin immunoprecipitation experiments, and phenotypic analysis allowed us to elucidate the role of CO over the circadian clock. Plants with altered CO expression showed a different internal clock period, measured by daily leaf rhythmic movements. We showed that CO upregulates the expression of key genes related to the circadian clock, such as CCA1, LHY, PRR5, and GI, at the end of a long day by binding to specific sites on their promoters. Moreover, a high number of PRR5-repressed target genes are upregulated by CO, and this could explain the phase transition promoted by CO. The CO-PRR5 complex interacts with the bZIP transcription factor HY5 and helps to localize the complex in the promoters of clock genes. Taken together, our results indicate that there may be a feedback loop in which CO communicates back to the circadian clock, providing seasonal information to the circadian system.

Regulation of floral senescence in Arabidopsis by coordinated action of CONSTANS and jasmonate signaling.

In Arabidopsis, photoperiodic flowering is controlled by the regulatory hub gene CONSTANS (CO), whereas floral organ senescence is regulated by the jasmonates (JAs). Because these processes are chronologically ordered, it remains unknown whether there are common regulators of both processes. In this study, we discovered that CO protein accumulates in Arabidopsis flowers after floral induction, and it displays a diurnal pattern in floral organs different from that in the leaves. We observed that altered CO expression could affect flower senescence and abscission by interfering with JA response, as shown by petal-specific transcriptomic analysis as well as CO overexpression in JA synthesis and signaling mutants. We found that CO has a ZIM (ZINC-FINGER INFLORESCENCE MERISTEM) like domain that mediates its interaction with the JA response repressor JAZ3 (jasmonate ZIM-domain 3). Their interaction inhibits the repressor activity of JAZ3, resulting in activation of downstream transcription factors involved in promoting flower senescence. Furthermore, we showed that CO, JAZ3, and the E3 ubiquitin ligase COI1 (Coronatine Insensitive 1) could form a protein complex in planta, which promotes the degradation of both CO and JAZ3 in the presence of JAs. Taken together, our results indicate that CO, a key regulator of photoperiodic flowering, is also involved in promoting flower senescence and abscission by augmenting JA signaling and response. We propose that coordinated recruitment of photoperiodic and JA signaling pathways could be an efficient way for plants to chronologically order floral processes and ensure the success of offspring production.

Characterization of the nasopharyngeal microbiome in patients with Kawasaki disease.

INTRODUCTION: The aetiology of Kawasaki disease (KD) remains unknown. Several studies have linked the human microbiome with some diseases. However, there are limited studies on the role of the respiratory microbiome in KD. The aim of our study was to make a more thorough analysis of the causes and processes that increase the susceptibility to KD. METHODS: Case-control study comparing the respiratory microbiome of KD patients with that of healthy children. The V3-V4 region of the 16S rRNA bacterial gene and 16 respiratory viruses were analysed by real-time polimerase-chain reaction. We used the Ribosomal Database Project (RDP) version 11.5 (taxonomic assignment). RESULTS: The initial sample included 11 cases and 11 controls matched for age, sex and seasonality. One of the cases was excluded to poor sample quality. The final analysis included 10 cases and 10 controls. In the case group, the analysis detected Haemophilus, Moraxella, Streptococcus and Corynebacterium species (27.62%, 19.71%, 25.28%, 11.86%, respectively). In the control group, it found Haemophilus, Streptococcus, Moraxella, and Dolosigranulum species (38.59%, 23.71%, 16.08, 8.93%, respectively). We found a higher relative abundance of Corynebacterium in patients with KD (11.86% vs. 1.55%; P = 0.004). CONCLUSIONS: To our knowledge, this is the first study that has found differences in the composition of the respiratory microbiome between patients with KD and healthy controls. The relative abundance of Corynebacterium spp. was greater in the KD group. This study shows differences in the microbiome between cases and controls, which suggests that the microbiome may play a role in facilitating the development of KD.

H2AK121ub in Arabidopsis associates with a less accessible chromatin state at transcriptional regulation hotspots.

Although it is well established that the Polycomb Group (PcG) complexes maintain gene repression through the incorporation of H2AK121ub and H3K27me3, little is known about the effect of these modifications on chromatin accessibility, which is fundamental to understand PcG function. Here, by integrating chromatin accessibility, histone marks and expression analyses in different Arabidopsis PcG mutants, we show that PcG function regulates chromatin accessibility. We find that H2AK121ub is associated with a less accessible but still permissive chromatin at transcriptional regulation hotspots. Accessibility is further reduced by EMF1 acting in collaboration with PRC2 activity. Consequently, H2AK121ub/H3K27me3 marks are linked to inaccessible although responsive chromatin. In contrast, only-H3K27me3-marked chromatin is less responsive, indicating that H2AK121ub-marked hotspots are required for transcriptional responses. Nevertheless, despite the loss of PcG activities leads to increased chromatin accessibility, this is not necessarily accompanied by transcriptional activation, indicating that accessible chromatin is not always predictive of gene expression.

Evolution of Daily Gene Co-expression Patterns from Algae to Plants.

Daily rhythms play a key role in transcriptome regulation in plants and microalgae orchestrating responses that, among other processes, anticipate light transitions that are essential for their metabolism and development. The recent accumulation of genome-wide transcriptomic data generated under alternating light:dark periods from plants and microalgae has made possible integrative and comparative analysis that could contribute to shed light on the evolution of daily rhythms in the green lineage. In this work, RNA-seq and microarray data generated over 24 h periods in different light regimes from the eudicot Arabidopsis thaliana and the microalgae Chlamydomonas reinhardtii and Ostreococcus tauri have been integrated and analyzed using gene co-expression networks. This analysis revealed a reduction in the size of the daily rhythmic transcriptome from around 90% in Ostreococcus, being heavily influenced by light transitions, to around 40% in Arabidopsis, where a certain independence from light transitions can be observed. A novel Multiple Bidirectional Best Hit (MBBH) algorithm was applied to associate single genes with a family of potential orthologues from evolutionary distant species. Gene duplication, amplification and divergence of rhythmic expression profiles seems to have played a central role in the evolution of gene families in the green lineage such as Pseudo Response Regulators (PRRs), CONSTANS-Likes (COLs), and DNA-binding with One Finger (DOFs). Gene clustering and functional enrichment have been used to identify groups of genes with similar rhythmic gene expression patterns. The comparison of gene clusters between species based on potential orthologous relationships has unveiled a low to moderate level of conservation of daily rhythmic expression patterns. However, a strikingly high conservation was found for the gene clusters exhibiting their highest and/or lowest expression value during the light transitions.

Caracterización del microbioma nasofaríngeo en pacientes con enfermedad de Kawasaki / Characterization of the nasopharyngeal microbiome in patients with Kawasaki disease

Introducción: La etiología de la enfermedad de Kawasaki (EK) sigue siendo desconocida. Varios estudios han relacionado el microbioma humano con algunas enfermedades. Sin embargo, los estudios sobre el microbioma respiratorio en EK son limitados. Este estudio intenta profundizar en las causas y procesos que predisponen al desarrollo de la EK. Métodos: Estudio de casos y controles en el que se compara el microbioma respiratorio de pacientes con EK con el de niños sanos. La región V3-V4 del gen bacteriano del ARNr 16S y 16 virus respiratorios se analizaron mediante reacción en cadena de la polimerasa en tiempo real. Se utilizó la base de datos RDP (Ribosomal Database Project) versión 11.5 (asignación taxonómica). Resultados: Se incluyeron 11casos y 11 controles emparejados por edad, sexo y estacionalidad. Uno de los casos fue descartado por mala calidad de la muestra. El estudio final se realizó a 10 casos y 10 controles. En el grupo de casos se encontraron Haemophilus, Moraxella, Streptococcus y Corynebacterium (27,62%, 19,71%, 25,28% y 11,86%, respectivamente). En el grupo control, Haemophilus, Streptococcus, Moraxella y Dolosigranulum (38,59%, 23,71%, 16,08 y 8,93%, respectivamente). Corynebacterium mostró una mayor abundancia en pacientes con EK (11,86% vs. 1,55%; p = 0,004). Conclusiones: Hasta donde sabemos, este es el primer estudio que ha encontrado diferencias en la composición del microbioma respiratorio entre pacientes con EK y controles sanos. Corynebacterium spp. presentó una mayor abundancia en el grupo de EK. Este estudio muestra diferencias en el microbioma entre pacientes y controles, lo que sugiere un papel facilitador del microbioma en el desarrollo de la EK. (AU)

Introduction: The aetiology of Kawasaki disease (KD) remains unknown. Several studies have linked the human microbiome with some diseases. However, there are limited studies on the role of the respiratory microbiome in KD. The aim of our study was to make a more thorough analysis of the causes and processes that increase the susceptibility to KD. Methods: Case-control study comparing the respiratory microbiome of KD patients with that of healthy children. The V3–V4 region of the 16S rRNA bacterial gene and 16 respiratory viruses were analysed by real-time polimerase-chain reaction. We used the Ribosomal Database Project (RDP) version 11.5 (taxonomic assignment). Results: The initial sample included 11 cases and 11 controls matched for age, sex and seasonality. One of the cases was excluded to poor sample quality. The final analysis included 10 cases and 10 controls. In the case group, the analysis detected Haemophilus, Moraxella, Streptococcus and Corynebacterium species (27.62%, 19.71%, 25.28%, 11.86%, respectively). In the control group, it found Haemophilus, Streptococcus, Moraxella, and Dolosigranulum species (38.59%, 23.71%, 16.08, 8.93%, respectively). We found a higher relative abundance of Corynebacterium in patients with KD (11.86% vs. 1.55%; P=.004). Conclusions: To our knowledge, this is the first study that has found differences in the composition of the respiratory microbiome between patients with KD and healthy controls. The relative abundance of Corynebacterium spp. was greater in the KD group. This study shows differences in the microbiome between cases and controls, which suggests that the microbiome may play a role in facilitating the development of KD. (AU)

Characterization of the Sucrose Phosphate Phosphatase (SPP) Isoforms from Arabidopsis thaliana and Role of the S6PPc Domain in Dimerization.

Sucrose-phosphate phosphatase (SPP) catalyses the final step in the sucrose biosynthesis pathway. Arabidopsis thaliana genome codifies four SPP isoforms. In this study, the four Arabidopsis thaliana genes coding for SPP isoforms have been cloned, expressed in Escherichia coli and the kinetic and regulatory properties of the purified enzymes analysed. SPP2 is the isoform showing the highest activity, with SPP3b and SPP3a showing lower activity levels. No activity was detected for SPP1. We propose that this lack of activity is probably due to the absence of an essential amino acid participating in catalysis and/or in the binding of the substrate, sucrose-6-phosphate (Suc6P). The expression patterns of Arabidopsis SPP genes indicate that SPP2 and SPP3b are the main isoforms expressed in different tissues and organs, although the non-catalytic SPP1 is the main isoform expressed in roots. Thus, SPP1 could have acquired new unknown functions. We also show that the three catalytically active SPPs from Arabidopsis are dimers. By generating a chimeric SPP composed of the monomeric cyanobacterial SPP fused to the higher plant non-catalytic S6PPc domain (from SPP2), we show that the S6PPc domain is responsible for SPP dimerization. This is the first experimental study on the functionality and gene expression pattern of all the SPPs from a single plant species.