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Oxygen is essential for plant growth and development. Hypoxia occurs in plants due to limited oxygen availability following adverse environmental conditions as well in hypoxic niches in otherwise normoxic environments. However, the existence and functional integration of spatiotemporal oxygen dynamics with plant development remains unknown. In animal systems dynamic fluctuations in oxygen availability are known as cyclic hypoxia. In this study, we demonstrate that cyclic fluctuations in internal oxygen levels occur in young emerging leaves of Arabidopsis plants. Cyclic hypoxia in plants is based on a mechanism requiring the ETHYLENE RESPONSE FACTORS type VII (ERFVII) that are central components of the oxygen-sensing machinery in plants. The ERFVII-dependent mechanism allows precise adjustment of leaf growth in response to carbon status and oxygen availability within plant cells. This study thus establishes a functional connection between internal spatiotemporal oxygen dynamics and developmental processes of plants.

Poplar trees use photoperiod as a precise seasonal indicator, synchronizing plant phenology with the environment. Daylength cue determines FLOWERING LOCUS T 2 (FT2) daily expression, crucial for shoot apex development and establishment of the annual growing period. However, limited evidence exists for the molecular factors controlling FT2 transcription and the conservation with the photoperiodic control of Arabidopsis flowering. We demonstrate that FT2 expression mediates growth cessation response quantitatively, and we provide a minimal data-driven model linking core clock genes to FT2 daily levels. GIGANTEA (GI) emerges as a critical inducer of the FT2 activation window, time-bound by TIMING OF CAB EXPRESSION (TOC1) and LATE ELONGATED HYPOCOTYL (LHY2) repressions. CRISPR/Cas9 loss-of-function lines validate these roles, identifying TOC1 as a long-sought FT2 repressor. Additionally, model simulations predict that FT2 downregulation upon daylength shortening results from a progressive narrowing of this activation window, driven by the phase shift observed in the preceding clock genes. This circadian-mediated mechanism enables poplar to exploit FT2 levels as an accurate daylength-meter.

Ectomycorrhizas are an intrinsic component of tree nutrition and responses to environmental variations. How epigenetic mechanisms might regulate these mutualistic interactions is unknown. By manipulating the level of expression of the chromatin remodeler DECREASE IN DNA METHYLATION 1 (DDM1) and two demethylases DEMETER-LIKE (DML) in Populus tremula × Populus alba lines, we examined how host DNA methylation modulates multiple parameters of the responses to root colonization with the mutualistic fungus Laccaria bicolor. We compared the ectomycorrhizas formed between transgenic and wild-type (WT) trees and analyzed their methylomes and transcriptomes. The poplar lines displaying lower mycorrhiza formation rate corresponded to hypomethylated overexpressing DML or RNAi-ddm1 lines. We found 86 genes and 288 transposable elements (TEs) differentially methylated between WT and hypomethylated lines (common to both OX-dml and RNAi-ddm1) and 120 genes/1441 TEs in the fungal genome suggesting a host-induced remodeling of the fungal methylome. Hypomethylated poplar lines displayed 205 differentially expressed genes (cis and trans effects) in common with 17 being differentially methylated (cis). Our findings suggest a central role of host and fungal DNA methylation in the ability to form ectomycorrhizas including not only poplar genes involved in root initiation, ethylene and jasmonate-mediated pathways, and immune response but also terpenoid metabolism.

Gene functional descriptions offer a crucial line of evidence for candidate genes underlying trait variation. Conversely, plant responses to environmental cues represent important resources to decipher gene function and subsequently provide molecular targets for plant improvement through gene editing. However, biological roles of large proportions of genes across the plant phylogeny are poorly annotated. Here we describe the Joint Genome Institute (JGI) Plant Gene Atlas, an updateable data resource consisting of transcript abundance assays spanning 18 diverse species. To integrate across these diverse genotypes, we analyzed expression profiles, built gene clusters that exhibited tissue/condition specific expression, and tested for transcriptional response to environmental queues. We discovered extensive phylogenetically constrained and condition-specific expression profiles for genes without any previously documented functional annotation. Such conserved expression patterns and tightly co-expressed gene clusters let us assign expression derived additional biological information to 64 495 genes with otherwise unknown functions. The ever-expanding Gene Atlas resource is available at JGI Plant Gene Atlas (https://plantgeneatlas.jgi.doe.gov) and Phytozome (https://phytozome.jgi.doe.gov/), providing bulk access to data and user-specified queries of gene sets. Combined, these web interfaces let users access differentially expressed genes, track orthologs across the Gene Atlas plants, graphically represent co-expressed genes, and visualize gene ontology and pathway enrichments.

Plant growth and development involve the specification and regeneration of stem cell niches (SCNs). Although plants are exposed to disparate environmental conditions, how environmental cues affect developmental programs and stem cells is not well understood. Root stem cells are accommodated in meristems in SCNs around the quiescent center (QC), which maintains their activity. Using a combination of genetics and confocal microscopy to trace morphological defects and correlate them with changes in gene expression and protein levels, we show that the cold-induced transcription factor (TF) C-REPEAT BINDING FACTOR 3 (CBF3), which has previously been associated with cold acclimation, regulates root development, stem cell activity, and regeneration. CBF3 is integrated into the SHORT-ROOT (SHR) regulatory network, forming a feedback loop that maintains SHR expression. CBF3 is primarily expressed in the root endodermis, whereas the CBF3 protein is localized to other meristematic tissues, including root SCNs. Complementation of cbf3-1 using a wild-type CBF3 gene and a CBF3 fusion with reduced mobility show that CBF3 movement capacity is required for SCN patterning and regulates root growth. Notably, cold induces CBF3, affecting QC activity. Furthermore, exposure to moderate cold around 10°C-12°C promotes root regeneration and QC respecification in a CBF3-dependent manner during the recuperation period. By contrast, CBF3 does not appear to regulate stem cell survival, which has been associated with recuperation from more acute cold (∼4°C). We propose a role for CBF3 in mediating the molecular interrelationships among the cold response, stem cell activity, and development.

The adaptation and survival of boreal and temperate perennials relies on the precise demarcation of the growing season. Seasonal growth and development are defined by day length and temperature signals. Under long-day conditions in spring, poplar FLOWERING LOCUS T2 (FT2) systemically induces shoot growth. In contrast, FT2 downregulation induced by autumnal short days triggers growth cessation and bud set. However, the molecular role of FT2 in local and long-range signaling is not entirely understood. In this study, the CRISPR/Cas9 editing tool was used to generate FT2 loss of function lines of hybrid poplar. Results indicate that FT2 is essential to promote shoot apex development and restrict internode elongation under conditions of long days. The application of bioactive gibberellins (GAs) to apical buds in FT2 loss of function lines was able to rescue bud set. Expression analysis of GA sensing and metabolic genes and hormone quantification revealed that FT2 boosts the 13-hydroxylation branch of the GA biosynthesis pathway in the shoot apex. Paclobutrazol treatment of WT leaves led to limited internode growth in the stem elongation zone. In mature leaves, FT2 was found to control the GA 13-hydroxylation pathway by increasing GA2ox1 and reducing GA3ox2 expression, causing reduced GA1 levels. We here show that in poplar, the FT2 signal promotes shoot apex development and restricts internode elongation through the GA 13-hydroxylation pathway.

The aim of this study is to design a biohybrid neural interface capable of performing synapses with a motor neuron. Following the technology of graphene-based field-effect transistors (gFET), a device capable of generating an electrical signal when the neurotransmitter acetylcholine (ACh) is released has been developed. This device consists of two gold electrodes acting as a drainer and transistor source with a graphene gate. Graphene is a biocompatible material sensitive to pH changes, changing its conductive properties depending on the concentration of protons in the medium. Acetylcholinesterase (AChE) is an enzyme present in neurons of the peripheral nervous system and is capable of hydrolyzing ACh into acetate and choline, releasing protons. The method of detection of ACh is based on the catalytic activity of AChE. To immobilize the AChE enzyme in the gold electrodes of the gFET, a Silanization by Activated Steam (AVS) process has been studied to functionalize titanium sheets metallized with gold. This technique coats the gold surface with a high density of primary amino groups. Utilizing the chemistry of the crosslinkers it is intended to immobilize the enzyme covalently and permanently Immobilization of AChE by crosslinkers N-(3 Dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) was achieved by a stable but non-durable amide bond. On the other hand, immobilization by the crosslinker sulfosuccinimidil 6-(3'-(2-pyridyldithio) propionamido) hexanoate (sulfo-LC-SPDP) was not achieved, but it has been shown that its binding to AChE does not prevent the catalytic activity of the enzyme.

En los inicios de la enfermedad pandémica por coronavirus (COVID-19), causada por el síndrome respiratorio agudo severo coronavirus 2 (SARS-CoV-2) presenta una gravedad variable desde episodios asintomáticos hasta muy graves. El COVID-19, de la familia Coronaviridie, afecta principalmente a las vías respiratorias que produce tos seca, fiebre, mialgia, dolor de cabeza, fatiga hasta una neumonía intersticial e insuficiencia respiratoria grave. Sin embargo, algunos de estos pacientes registraron manifestaciones cutáneas y lesiones del sistema vascular fuera de la esfera respiratoria como síndromes autoinflamatorios severos (fiebre mediterránea familiar, dermatosis neutrofílicas), erupciones vesiculares, urticarianas y maculopapulares, livedo, necrosis y otras formas de vasculitis o síndromes DRESS conocidos por reacciones adversas hacia fármacos. Se desconocen los mecanismos por el que se lleva cabo estas lesiones cutáneas que se han ido relacionando con mayor frecuencia dentro del cuadro infeccioso COVID-19. Estos síntomas pueden estar provocados por una infección viral, una respuesta adversa hacia el fármaco o ambos. Además, estos signos clínicos pueden empeorar acorde a la susceptibilidad de los pacientes ligada a los antígenos leucocitarios humanos (HLA) que pueden provocar una tormenta inmune que causa un daño multiorgánico e incluso la muerte. El objetivo principal de este Trabajo de Fin de Grado consiste en estudiar la importancia del papel de la respuesta celular en las lesiones cutáneas inducidos por virus y por fármacos a través de la prueba de transformación de linfocitos (LTT). Estos basados en la capacidad de las células T de memoria del paciente específicas del fármaco para que proliferen una vez que hayan sido estimuladas por un antígeno. Los resultados obtenidos muestran si los linfocitos han proliferado sobre los diferentes tratamientos genéricos que se usaron en la primera oleada COVID-19: Azitromicina, Amoxicilina, Ácido Clavulánico, Hidroxicloroquin

Woody perennials adapt their genetic traits to local climate conditions. Day length plays an essential role in the seasonal growth of poplar trees. When photoperiod falls below a given critical day length, poplars undergo growth cessation and bud set. A leaf-localized mechanism of photoperiod measurement triggers the transcriptional modulation of a long distance signaling molecule, FLOWERING LOCUS T (FT). This molecule targets meristem function giving rise to these seasonal responses. Studies over the past decade have identified conserved orthologous genes involved in photoperiodic flowering in Arabidopsis that regulate poplar vegetative growth. However, phenological and molecular examination of key photoperiod signaling molecules reveals functional differences between these two plant model systems suggesting alternative components and/or regulatory mechanisms operating during poplar vegetative growth. Here, we review current knowledge and provide new data regarding the molecular components of the photoperiod measuring mechanism that regulates annual growth in poplar focusing on main achievements and new perspectives.

Woody perennials adapt their genetic traits to local climate conditions. Day length plays an essential role in the seasonal growth of poplar trees. When photoperiod falls below a given critical day length, poplars undergo growth cessation and bud set. A leaf-localized mechanism of photoperiod measurement triggers the transcriptional modulation of a long distance signaling molecule, FLOWERING LOCUS T (FT). This molecule targets meristem function giving rise to these seasonal responses. Studies over the past decade have identified conserved orthologous genes involved in photoperiodic flowering in Arabidopsis that regulate poplar vegetative growth. However, phenological and molecular examination of key photoperiod signaling molecules reveals functional differences between these two plant model systems suggesting alternative components and/or regulatory mechanisms operating during poplar vegetative growth. Here, we review current knowledge and provide new data regarding the molecular components of the photoperiod measuring mechanism that regulates annual growth in poplar focusing on main achievements and new perspectives.

As sessile organism, plants require adaptive mechanisms to fit its development with their local environment. The adaptative versatility is especially meaningful for woody perennials trees from temperate and boreal regions, long-life organisms that have to deal with the harsh winter conditions year after year. With the aim to survive to this season, perennials have evolved the vegetative growth-dormancy phenological transition. During winter dormancy plants enter in a growth quiescent state resistant to freezing and drought stress. In poplar, the shortening of daylength leads to shoot apical growth cessation that is the gateway of dormancy establishment. During last decade, molecular components mediating this photoperiodic control of growth cessation have started to emerge, however understanding the mechanism involved require deeper analysis. Previous studies performed in the laboratory, using poplar as the experimental system, proved that the photoperiod integrator and growth inductor FLOWERING LOCUS T 2 (FT2), is quantitatively repressed in response to the extension of the night. An investigation of the photoperiodic repression route was initiated revealing that the clock gene LATE ELONGATED HYPOCOTYL 2 (LHY2) is involved. Moreover, it was identified the phytochrome signalling pathway as the responsible for perceiving and transferring the photoperiodic external information to LHY2. These results have led to hypothesize that a novel pathway senses the progressive extension of the night and eventually represses FT2 expression, causing poplar shoot apical growth cessation. The purpose of this work is to provide new experimental evidences that support this model, focusing on understanding the photoperiodic control of LHY2 transcription. This study evidences that night break assays, where poplars were subjected to a red-light pulse in the middle of the night, release the repression of FT2 and subsequently the bud set establishment triggered under short days. Moreover, i

Precise control of gene expression is essential to synchronize plant development with the environment. In perennial plants, transcriptional regulation remains poorly understood, mainly due to the long time required to perform functional studies. Transcriptional reporters based on luciferase have been useful to study circadian and diurnal regulation of gene expression, both by transcription factors and chromatin remodelers. The high mobility group proteins are considered transcriptional chaperones that also modify the chromatin architecture. They have been found in several species, presenting in some cases a circadian expression of their mRNA or protein. Results: Transactivation experiments have been shown as a powerful and fast method to obtain information about the potential role of transcription factors upon a certain reporter. We designed and validated a luciferase transcriptional reporter using the 5? sequence upstream ATG of Populus tremula × alba LHY2 gene. We showed the robustness of this reporter line under long day and continuous light conditions. Moreover, we confirmed that pPtaLHY2::LUC activity reproduces the accumulation of PtaLHY2 mRNA. We performed transactivation studies by transient expression, using the reporter line as a genetic background, unraveling a new function of a high mobility group protein in poplar, which can activate the PtaLHY2 promoter in a gate-dependent manner. We also showed PtaHMGB2/3 needs darkness to produce that activation and exhibits an active degradation after dawn, mediated by the 26S proteasome. Conclusions: We generated a stable luciferase reporter poplar line based on the circadian clock gene PtaLHY2, which can be used to investigate transcriptional regulation and signal transduction pathway. Using this reporter line as a genetic background, we established a methodology to rapidly assess potential regulators of diurnal and circadian rhythms. This tool allowed us to demonstrate that PtaHMGB2/3 promotes the transcriptional