A quantitative gibberellin signaling biosensor reveals a role for gibberellins in internode specification at the shoot apical meristem

Growth at the shoot apical meristem (SAM) is essential for shoot architecture construction. The phytohormones gibberellins (GA) play a pivotal role in coordinating plant growth, but their role in the SAM remains mostly unknown. Here, we developed a ratiometric GA signaling biosensor by engineering one of the DELLA proteins, to suppress its master regulatory function in GA transcriptional responses while preserving its degradation upon GA sensing. We demonstrate that this degradation-based biosensor accurately reports on cellular changes in GA levels and perception during development. We used this biosensor to map GA signaling activity in the SAM. We show that high GA signaling is found primarily in cells located between organ primordia that are the precursors of internodes. By gain- and loss-of-function approaches, we further demonstrate that GAs regulate cell division plane orientation to establish the typical cellular organization of internodes, thus contributing to internode specification in the SAM.

Mathematical Modeling of Photo- and Thermomorphogenesis in Plants

Increased day lengths and warm conditions inversely affect plant growth by directly modulating nuclear phyB, ELF3, and COP1 levels. Quantitative measures of the hypocotyl length have been key to gaining a deeper understanding of this complex regulatory network, while similar quantitative data are the foundation for many studies in plant biology. Here, we explore the application of mathematical modeling, specifically ordinary differential equations (ODEs), to understand plant responses to these environmental cues. We provide a comprehensive guide to constructing, simulating, and fitting these models to data, using the law of mass action to study the evolution of molecular species. The fundamental principles of these models are introduced, highlighting their utility in deciphering complex plant physiological interactions and testing hypotheses. This brief introduction will not allow experimentalists without a mathematical background to run their own simulations overnight, but it will help them grasp modeling principles and communicate with more theory-inclined colleagues.

25 Years of thermomorphogenesis research: milestones and perspectives

In 1998, Bill Gray and colleagues showed that warm temperatures trigger arabidopsis hypocotyl elongation in an auxin-dependent manner. This laid the foundation for a vibrant research discipline. With several active members of the 'thermomorphogenesis' community, we here reflect on 25 years of elevated ambient temperature research and look to the future.

Long-distance control of potato storage organ formation by SELF PRUNING 3D and FLOWERING LOCUS T-like 1

Plants program their meristem-associated developmental switches for timely adaptation to a changing environment. Potato (Solanum tuberosum L.) tubers differentiate from specialized belowground branches or stolons through radial expansion of their terminal ends. During this process, the stolon apex and closest axillary buds enter a dormancy state that leads to tuber eyes, which are reactivated the following spring and generate a clonally identical plant. The potato FLOWERING LOCUS T homolog SELF-PRUNING 6A (StSP6A) was previously identified as the major tuber-inducing signal that integrates day-length cues to control the storage switch. However, whether some other long-range signals also act as tuber organogenesis stimuli remains unknown. Here, we show that the florigen SELF PRUNING 3D (StSP3D) and FLOWERING LOCUS T-like 1 (StFTL1) genes are activated by short days, analogously to StSP6A. Overexpression of StSP3D or StFTL1 promotes tuber formation under non-inductive long days, and the tuber-inducing activity of these proteins is graft transmissible. Using the non-tuber-bearing wild species Solanum etuberosum, a natural SP6A null mutant, we show that leaf-expressed SP6A is dispensable for StSP3D long-range activity. StSP3D and StFTL1 mediate secondary activation of StSP6A in stolon tips, leading to amplification of this tuberigen signal. StSP3D and StFTL1 were observed to bind the same protein partners as StSP6A, suggesting that they can also form transcriptionally active complexes. Together, our findings show that additional mobile tuber-inducing signals are regulated by the photoperiodic pathway.

A mini-TGA protein modulates gene expression through heterogeneous association with transcription factors

TGA (TGACG-binding) transcription factors, which bind their target DNA through a conserved basic region leucine zipper (bZIP) domain, are vital regulators of gene expression in salicylic acid (SA)-mediated plant immunity. Here, we investigated the role of StTGA2.1, a potato (Solanum tuberosum) TGA lacking the full bZIP, which we named a mini-TGA. Such truncated proteins have been widely assigned as loss-of-function mutants. We, however, confirmed that StTGA2.1 overexpression compensates for SA-deficiency, indicating a distinct mechanism of action compared with model plant species. To understand the underlying mechanisms, we showed that StTGA2.1 can physically interact with StTGA2.2 and StTGA2.3, while its interaction with DNA was not detected. We investigated the changes in transcriptional regulation due to StTGA2.1 overexpression, identifying direct and indirect target genes. Using in planta transactivation assays, we confirmed that StTGA2.1 interacts with StTGA2.3 to activate StPRX07, a member of class III peroxidases (StPRX), which are known to play role in immune response. Finally, via structural modeling and molecular dynamics simulations, we hypothesized that the compact molecular architecture of StTGA2.1 distorts DNA conformation upon heterodimer binding to enable transcriptional activation. This study demonstrates how protein truncation can lead to distinct functions and that such events should be studied carefully in other protein families.

Analysis of myocardial salvage with cardiac magnetic ressonance and angiography depending on the STEMI revascularization pathway in a PPCI centre

Background

Reperfusion networks have permitted improvements in reperfusion delays in primary percutaneous coronary intervention (PPCI)-treated ST elevation myocardial infarction (STEMI). However, the impact on myocardial salvage (MS) of direct transfer to the catheterization laboratory (cath-lab) to minimize system delay remains unknown.

Objective

We sought to quantify the myocardial salvage index (MSI) acutely and to assess adverse remodeling at 6 months in PPCI-treated STEMI according to the mode of patient presentation.

Methods

Between 2005 and 2021 we included 493 patients in a single center registry of first PPCI-treated STEMI who were studied with Late gadolinium enhanced (LGE) cardiac magnetic resonance (CMR) in the acute phase. Among them, 414 (84.0%) underwent a second LGE-CMR at 6 months. Subjects were classified depending on the mode of presentation: those diagnosed out-of-hospital and directly transferred to the cath-lab by the Emergency Medical Services (EMS group, 29.82%); subjects with first medical contact in a PCI-capable hospital (PCI-H group, 41.75%); and patients presenting to a non-PCI-capable center and transferred for PCI (non-PCI-H group, 28.43%). We computed the angiographic area at risk by BARI score, and combined it with the LGE-CMR derived infarct size to compute a validated MSI, expressed as percentage of area at risk. The change in ejection fraction (EF) and indexed left ventricle end-diastolic volume (iLVEDV) from baseline to 6 months was also computed.

Results

The mean age was 58.9±11.9 years, 84.5% were male and 51.4% had anterior STEMI. Total median ischaemic time was (median (interquartile range)) 126 (105–161) min in the EMS group, 201 (145–321) min in the PCI-H group and 300 (173–592) min in the non-PCI-H group (p<0.01). MSI was 45.28±2.6%, 39.63±2.2% and 35.53±2.7% respectively (p=0.034). In a multiple linear regression model adjusting for relevant covariables, including initial TIMI flow, area at risk, Killip class, age, sex, diabetes, number of vessels and presence of collaterals, a 7.50% (95% CI 0.9 to 14.1%) increase in MSI was observed in the EMS group compared to the PCI-H group, and 11.03% (95% CI 3.9 to 18.2%) compared to the non-PCI-H group (p=0.027 and 0.003 respectively). At 6 months, the mean absolute increase in EF was 5.36±0.6% for the EMS group, 4.03±0.5% for the PCI-H group and 3.52±0.6% for the non-PCI-H group (p<0.05 in the adjusted analysis) and the increase in iLVEDV was 2.37±7.3, 5.51±6.6 and 18.30±7.6 mL/m2 respectively (p=0.28).

Conclusions

Patients with out-of-hospital diagnostis of STEMI by the EMS who were directly transferred to the cath-lab showed shorter total ischaemic times, resulting in increased myocardial salvage and a trend towards improved indexes of left ventricular function at 6 months.

Funding Acknowledgement

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Grant from La Maratό de TV3 and grant from Fundaciό La Caixa

Cardiac injury before and after COVID-19. A longitudinal MRI study

Background

Recent MRI-based studies have raised great concern about frequent cardiac involvement even in mild or asymptomatic COVID-19. However, while signs of myocardial injury were found in large proportions of patients after COVID-19, all studies published to date lack baseline imaging and are therefore unable to discriminate between pre-existing and COVID-19-induced injury.

Purpose

In this longitudinal study, we aimed to assess the true cardiac impact of COVID-19 based on pre- and post-COVID-19 late gadolinium enhancement (LGE)-MRI.

Methods

A prospective registry of patients with serial LGE-MRIs was screened for patients with documented SARS-COV-2 infection after cardiac LGE-MRI. Eligible patients then received a post-COVID-19 LGE-MRI using the same scanner and sequence as in the pre-COVID-19 MRI. Inversion recovery prepared T1-weighted gradient echo sequences were acquired in sinus rhythm using ECG gating and a free-breathing 3D navigator, 15–20 minutes after administering an intravenous bolus of 0.2 mmol/kg of gadobutrol. A TI scout sequence was used in order to determine the optimal TI that nullified the left ventricular myocardial signal. The presence of LGE was independently assessed qualitatively by two experienced investigators blinded to patient information. For quantitative analyses a 3D-reconstruction of the left ventricle was performed using ADAS-3D software. LGE was then automatically quantified based on a prespecified signal intensity threshold of ≥3 SD above the mean of a remote non-enhanced myocardial region.

Results

Pre- and post-COVID LGE-MRI from 31 patients with cardiovascular risk factors that had recovered from mild to moderate COVID-19 (23% hospitalised) were analysed. At a median of 5 months post-COVID-19, LGE-lesions indicative of myocardial injury were encountered in 15 out of 31 patients (48%), which is in line with previous reports. However, intraindividual comparison with the pre-COVID-19 MRI reveiled all of these lesions as pre-existing and thus not COVID-19-related. Quantitative analysis detected no increase in the size of individual LGE-lesions, nor in the global left ventricular LGE-extent. There was no difference in any functional or structural parameter between pre- and post-COVID-19 MRI.

Conclusion

This longitudinal study in a cohort of patients considered at high risk of cardiac involvement, did not find any evidence for COVID-19-induced myocardial injury. The complete absence of de novo LGE lesions in this cohort is reassuring and indicates that cardiac sequelae of COVID-19 are rare and certainly not as common as previously suggested.

Funding Acknowledgement

Type of funding sources: None.

COP1 dynamics integrate conflicting seasonal light and thermal cues in the control of Arabidopsis elongation

As the summer approaches, plants experience enhanced light inputs and warm temperatures, two environmental cues with an opposite morphogenic impact. Key components of this response are PHYTOCHROME B (phyB), EARLY FLOWERING 3 (ELF3), and CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1). Here, we used single and double mutant/overexpression lines to fit a mathematical model incorporating known interactions of these regulators. The fitted model recapitulates thermal growth of all lines used and correctly predicts thermal behavior of others not used in the fit. While thermal COP1 function is accepted to be independent of diurnal timing, our model shows that it acts at temperature signaling only during daytime. Defective response of cop1-4 mutants is epistatic to phyB-9 and elf3-8, indicating that COP1 activity is essential to transduce phyB and ELF3 thermosensory function. Our thermal model provides a unique toolbox to identify best allelic combinations enhancing climate change resilience of crops adapted to different latitudes.

Hysteresis in PHYTOCHROME-INTERACTING FACTOR 4 and EARLY-FLOWERING 3 dynamics dominates warm daytime memory in Arabidopsis

Despite the identification of temperature sensors and downstream components involved in promoting stem growth by warm temperatures, when and how previous temperatures affect current plant growth remain unclear. Here we show that hypocotyl growth in Arabidopsis thaliana during the night responds not only to the current temperature but also to preceding daytime temperatures, revealing a short-term memory of previous conditions. Daytime temperature affected the levels of PHYTOCHROME-INTERACTING FACTOR 4 (PIF4) and LONG HYPOCOTYL 5 (HY5) in the nucleus during the next night. These factors jointly accounted for the observed growth kinetics, whereas nighttime memory of prior daytime temperature was impaired in pif4 and hy5 mutants. PIF4 promoter activity largely accounted for the temperature-dependent changes in PIF4 protein levels. Notably, the decrease in PIF4 promoter activity triggered by cooling required a stronger temperature shift than the increase caused by warming, representing a typical hysteretic effect; this hysteretic pattern required EARLY-FLOWERING 3 (ELF3). Warm temperatures promoted the formation of nuclear condensates of ELF3 in hypocotyl cells during the afternoon but not in the morning. These nuclear speckles showed poor sensitivity to subsequent cooling. We conclude that ELF3 achieves hysteresis and drives the PIF4 promoter into the same behavior, enabling a short-term memory of daytime temperature conditions.

Spatial control of potato tuberization by the TCP transcription factor BRANCHED1b

The control of carbon allocation, storage and usage is critical for plant growth and development and is exploited for both crop food production and CO₂ capture. Potato tubers are natural carbon reserves in the form of starch that have evolved to allow propagation and survival over winter. They form from stolons, below ground, where they are protected from adverse environmental conditions and animal foraging. We show that BRANCHED1b (BRC1b) acts as a tuberization repressor in aerial axillary buds, which prevents buds from competing in sink strength with stolons. BRC1b loss of function leads to ectopic production of aerial tubers and reduced underground tuberization. In aerial axillary buds, BRC1b promotes dormancy, abscisic acid responses and a reduced number of plasmodesmata. This limits sucrose accumulation and access of the tuberigen protein SP6A. BRC1b also directly interacts with SP6A and blocks its tuber-inducing activity in aerial nodes. Altogether, these actions help promote tuberization underground.

[Not Available]

INTRODUCTION

Total knee arthroplasty (TKA) is a surgery that aims to restore function and relieve pain in advanced osteoarthritis. The Educational Workshop (EW) for TKA is given to patients in the pre-surgery period to inform them and facilitating their participation in their health process (empowerment). The aim of this study was developing and validating a self-administered questionnaire to evaluate the acquired knowledge after the EW by the patients who will undergo the TKA procedure.

MATERIAL AND METHODS

It was a longitudinal and prospective observational study with a sample of TKA candidate patients. The phases for the construction and validation of this ad hoc questionnaire were: Phase 1: A panel of experts who agreed on a final questionnaire of 20 items; Phase 2: Pilot test administered to 47 patients; Phase 3: Final test of 11 items administered to 50 patients, before and after the EW; Phase 4: Re-test, after the EW and 2 weeks after, administered to 58 patients.

RESULTS

One hundred and fifty five patients were included. The Cronbach's alpha coefficient for the item's internal consistency of the final questionnaire, 11 items, was 0.78. To reach the criterion validity, in pre-EW the mean number of hits was: 4.92 (SD=1.78) and in post-EW 10.68 (SD=0.55), a difference that had a statistical significance p<.0001, with no overlap in the 95% CI of the mean: 4.46-5.38/10.54-10.82. The test for stability and reliability, re-test, obtained a mean of right answers 10.87 (SD=0.33) and for the re-test of 10.70 (SD=0.59). The correlation of the interclass coefficient for the re-test was 0.99, which corresponds almost to a maximum concordance.

CONCLUSIONS

The questionnaire developed in this study is a reliable and easy tool to evaluate the acquired knowledge in the EW for patients who will be TKA operated.

Exploring phenotypes in hypertrophic cardiomyopathy with machine learning data integration. A multicentric, multimodality pilot study

Background

Interpreting patient phenotypes is a challenge when screening for hypertrophic cardiomyopathy (HCM). Machine learning (ML) can potentially help with advanced data integration - combining information contained in whole-cardiac cycle echo deformation and velocity profiles with standard clinical variables. The aim is to apply an ML approach to integrate whole cardiac cycle echo data with clinical variables to explore HCM phenotypes.

Methods

The cohort consisted of 138 participants from two centres: HCM patients (n=91) and relatives (n=47). Echocardiography was performed, whereas magnetic resonance and genetic testing in 48% and 82%, respectively. Whole cardiac cycle echo data (mitral and aortic velocity profiles, and six regional left ventricular (LV) deformation curves) were combined with clinical variables (age, sex, heart rate, e' medial and e' lateral) and used as the ML input. An unsupervised ML algorithm created a representative space where participants were positioned based on integrated data, blinded to disease status. Clustering was used to determine phenogroups and estimate the average characteristics. Data on family history (FHx), genotype, arrhythmias or syncope, implantable cardioverter-defibrillators (ICD), and late gadolinium enhancement (LGE) were used to interpret the phenogroups. As the LA diameter was not available in the dataset, the HCM risk for sudden cardiac death (SCD) was not calculated, however, the Table shows relevant variables to infer clinical risk.

Results

Clustering divided the participants into 6 phenogroups (P1–6) (Figure). Average echo profiles are shown in the Figure, while the clinical data in the Table. P1/2 was defined by symptomatic patients with a high prevalence of positive genotypes, a positive FHx of SCD, and a burden of comorbidities. Echo findings showed pronounced structural/functional remodeling, and P1 was associated with severe septal hypertrophy and outflow tract obstruction. The high prevalence of ICD devices defined P1/2 as high risk groups. In comparison, patients in P3/4 were younger, with milder LV hypertrophy, but still considerable functional impairment. P3 had a higher burden of FHX and a higher prevalence of pathogenic mutations, whereas P4 a higher incidence of hypertension, high heart rate, mitral inflow fusion and findings of LGE. Finally, P5/6 consisted of younger individuals, predominantly HCM relatives, with a mild phenotype and, thus, low inferred risk. As expected, the majority of patients with the genetic variants of undetermined significance were located in P5.

Conclusion

ML can help derive clinically interpretable phenotypes in HCM based on the automated integration of whole cardiac cycle deformation and velocity data with conventional clinical parameters. The derived phenogroups correspond with established risk profiles in HCM. An expanded dataset is needed to enable further exploration of the phenotype-genotype relations and to define prognostic value.

Funding Acknowledgement

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): This work was supported by the Horizon 2020 European Commission Project H2020-MSCA-ITN

Precise transcriptional control of cellular quiescence by BRAVO/WOX5 complex in Arabidopsis roots

Understanding stem cell regulatory circuits is the next challenge in plant biology, as these cells are essential for tissue growth and organ regeneration in response to stress. In the Arabidopsis primary root apex, stem cell-specific transcription factors BRAVO and WOX5 co-localize in the quiescent centre (QC) cells, where they commonly repress cell division so that these cells can act as a reservoir to replenish surrounding stem cells, yet their molecular connection remains unknown. Genetic and biochemical analysis indicates that BRAVO and WOX5 form a transcription factor complex that modulates gene expression in the QC cells to preserve overall root growth and architecture. Furthermore, by using mathematical modelling we establish that BRAVO uses the WOX5/BRAVO complex to promote WOX5 activity in the stem cells. Our results unveil the importance of transcriptional regulatory circuits in plant stem cell development.

Biomechanical demands of percussive techniques in the context of early stone toolmaking

Recent discoveries in archaeology and palaeoanthropology highlight that stone tool knapping could have emerged first within the genera Australopithecus or Kenyanthropus rather than Homo. To explore the implications of this hypothesis determining the physical demands and motor control needed for performing the percussive movements during the oldest stone toolmaking technology (i.e. Lomekwian) would help. We analysed the joint angle patterns and muscle activity of a knapping expert using three stone tool replication techniques: unipolar flaking on the passive hammer (PH), bipolar (BP) flaking on the anvil, and multidirectional and multifacial flaking with free hand (FH). PH presents high levels of activity for Biceps brachii and wrist extensors and flexors. By contrast, BP and FH are characterized by high solicitation of forearm pronation. The synergy analyses depict a high muscular and kinematic coordination. Whereas the muscle pattern is very close between the techniques, the kinematic pattern is more variable, especially for PH. FH displays better muscle coordination and conversely lesser joint angle coordination. These observations suggest that the transition from anvil and hammer to freehand knapping techniques in early hominins would have been made possible by the acquisition of a behavioural repertoire producing an evolutionary advantage that gradually would have been beneficial for stone tool production.

Validation of a deep learning reconstruction framework for 3D delayed myocardial enhancement imaging

Funding Acknowledgements

Type of funding sources: None.

Introduction

Myocardial delayed enhancement (MDE) MRI plays an important role in the identification of several cardiac conditions, both ischemic and non-ischemic (e.g. myocarditis, IDC, amyloidosis). 3D imaging offers increased resolution, full heart coverage and better depiction of complex pathologies, but its image quality is limited by long acquisition times.

Deep learning (DL) models enable advanced reconstruction algorithms that yield regularized images in practical computation times. In this study we evaluate a novel 3D-DL reconstruction to overcome the trade-off between reconstructed quality and acquisition time on MDE data.

Methods

A group of 14 subjects referred for CMR (5 F / 9 M, 59 ± 11 y.o., 78 ± 13 kg) were scanned with a 3D MDE sequence prototype: SPGR with IR preparation, fat & spatial saturation, respiratory navigator, ARC 2x, FOV 40x40cm, ST 1.4-2.4mm, matrix 280²-320², FA 20deg, BW 62.5 kHz, TE 2.1 ± 0.1ms, TI based on a CINE IR scout. All were retrospectively reconstructed using a 3D DL algorithm, trained on a database of over 700 datasets to reconstruct high-quality images with adjustable noise reduction.

The images were compared with standard 3D Cartesian reconstruction by two experienced cardiologists, to identify alterations in morphology or contrast distribution. Noise was estimated using the intensity standard deviation on a blood pool ROI. Feature preservation was estimated using the structural similarity index (SSI).

Results

The new method improved perceived image quality without loss of structural information or resolution (fig 1). Quantitative analysis (fig 2) confirmed these results: The average coefficient of variation in the blood was 0.08 ± 0.02 in the reference and 0.05 ± 0.02 with the new method; Given a target image noise level, DL reconstruction yielded up to 10% better SSI, compared to anisotropic filtering.

The clinical review didn’t reveal diagnostically significant alterations of structure or uptake pattern. A perceived reduction of sharpness was initially reported but individual examination of landmarks (e.g. pulmonary and coronary arteries) confirmed that no relevant features were being lost with the new reconstruction.

Discussion

The 3D MDE images obtained with DL reconstruction improved the trade-off between image noise -estimated by the blood pool intensity deviation- and feature preservation -estimated by SSI-.

Consistent improvement of image quality without morphological alterations of diagnostic relevance indicates that the new method can be considered for clinical practice. The next step in the validation process will require testing the robustness over a large set of cases with heterogeneous acquisition settings.

Conclusion

We presented the preliminary evaluation of a deep learning reconstruction method with 3D myocardial delayed enhancement data. The results show systematic improvement of overall image quality without loss of relevant diagnostic information.

Abstract Figure.

Improving the robustness of MOLLI T1 maps with a dedicated motion correction algorithm

Funding Acknowledgements

Type of funding sources: None.

Introduction

Myocardial T1 mapping constitutes a reliable indicator of heart diseases related to changes of myocardial extracellular content (e.g. oedema, fibrosis) as well as fat, iron and amyloid content.

T1-mapping techniques rely on fitting a model to a series of MRI measurements. Alignment between these measurements is required for accurate T1 estimation. This is limited by triggering accuracy and patient motion. Image registration is often applied to improve the alignment. In the case of MOLLI series, registration is compromised by contrast variation between the images.

We present the validation of a new registration method, designed to account for the contrast properties of MOLLI data.

Methods

A cohort of 186 patients referred for a CMR was included in this study (115 M / 71 F; weight 75 ± 15 Kg; age 55 ± 16). Scans on a 3.0T MR included a MOLLI sequence with target parameters: 2D bSSFP, 160x148, pFOV 0.8-1.0, 1.4x1.4mm², ST 8mm, TE 1.4ms, TR 3.0ms, FA 35deg, NEX 1, BW 100kHz, 2x ASSET, 5(3)3.

Cartesian 2D reconstruction followed by motion correction was applied retrospectively. A new correction algorithm was implemented, based on a similarity criterion that accounted for T1 relaxation: It consisted of an iterative approach alternating polarity estimation, T1 fitting, relaxation simulation and frame registration. The coefficient of determination (R²) was used as a quality measure. A representative subset of the results was reviewed by two experienced cardiologists.

Results

All reconstructions (totalling 1133 2D MOLLI series) yielded qualitatively correct T1 maps. Results with the new method were compared to conventional motion correction and no correction.

The number of pixels with R²&gt;0.95 was 85%±9% with standard motion correction and 90%±7% with the new dedicated method. In terms of improvement w.r.t. uncorrected data, the standard method yielded +3%±8% and the new one +9%±8%. Motion correction caused noticeable performance degradation in 12% of cases with the standard method, compared to 0.2% with the proposed method.

The relative performance of the different methods can be appreciated in Figure 3.

Discussion

Despite T1 mapping techniques constituting a reliable diagnostic tool in cardiac imaging, they remain sensitive to patient motion and triggering inaccuracies, making them vulnerable to arrhythmia episodes.

Improving the similarity criterion by accounting for T1 relaxation significantly decreased the incidence of misregistration and subsequent T1 inaccuracies. Using the R² of the voxel-wise T1 fit as a surrogate of alignment allowed to confirm the increased robustness of the new, dedicated motion correction method for MOLLI series.

Conclusion

We have demonstrated a new reconstruction pipeline with built-in registration, optimized for MOLLI T1-mapping. Using a large database of clinical data, the new method has been shown to improve the robustness to motion of cardiac T1 mapping.

Abstract Figure.

Aetiology-discriminative multimodality imaging of hypertrophic cardiomyopathy: deformation patterns relate to synchrotron-based assessment of microstructural tissue remodelling

Funding Acknowledgements

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): Horizon 2020 European Commission Project H2020-MSCA-ITN-2016 (764738) and the Clinical Research in Cardiology grant from the Spanish Cardiac Society.

Background

The aetiology of left ventricular hypertrophy (LVH) is a relevant clinical challenge with consequences for patient management. Phenotypes resulting from hypertensive remodelling and sarcomere mutation often overlap. Synchrotron X-ray phase-contrast imaging (X-PCI) is a technique that can provide 3-dimensional detailed information on myocardial micro-structure non-destructively. The aim is to relate macrostructural/functional, non-invasive, imaging phenotypes of hypertrophic cardiomyopathy (HCM) to the underlying myocardial microstructure assessed with X-PCI.

Methods

Myocardial tissue samples were obtained from three patients (P1-3) with obstructive myocardial hypertrophy undergoing septal myectomy. Medical history and the 5-year HCM risk scores were evaluated. The patients were imaged with magnetic resonance imaging and echocardiography prior to procedure. Myocardial structure was assessed with wall thickness, late gadolinium enhancement (LGE), whereas function with speckle-tracking deformation (STE) and tissue Doppler imaging (TDI). Myectomy tissue was imaged with X-PCI in the TOMCAT beamline, using a multiscale propagation-based protocol combining a low-resolution (LR) and a high-resolution (HR) setup (5.8 and 0.7 um pixel size, respectively).

Results

The clinical and imaging data are shown in Fig 1. On initial assessment, wall thickness, LGE distribution, global longitudinal strain and septal TDI demonstrated a similar macrostructural and functional phenotype of P1 and P2, whereas P3 stood out with more severe hypertrophy, scarring and dysfunction. Additional regional deformation analysis with STE revealed reduced deformation in the basal and mid septum in P1, paired with a hypertensive pattern of post-systolic shortening (PSS) (yellow arrows). In comparison, in P2 and P3, deformation was more heterogeneous regionally, with regions of almost complete absence of deformation (orange arrows). Upon further exploration with TDI, areas with abnormal deformation were identified on the transition from basal to mid septum in both P2 and P3, whereas deformation was normal, but reduced in P1, and paired with PSS. LR X-PCI defined regions of interest to scan with HR (yellow frame), where HR revealed extensive interstitial fibrosis (orange arrow) with normal myocyte size and organisation in P1, compatible with severe hypertensive remodelling. However, in P2 and P3, patches of fibrosis (yellow arrow) paired with enlarged myocytes organized in visible disarray, considerably more prominent in P3, were both compatible with sarcomere-mutation HCM.

Conclusion

The results demonstrate multiscale phenotyping of HCM - relating micro- and macrostructural findings to function, and integrating multimodality data. In-depth regional deformation analysis, validated by synchrotron-based microstructural analysis, showed potential to identify distinct imaging phenotypes in HCM, distinguishing between overlapping presentations in different aetiologies.

Abstract Figure 1

SARS-CoV-2 Cysteine-like Protease Antibodies Can Be Detected in Serum and Saliva of COVID-19-Seropositive Individuals

Currently, there is a need for reliable tests that allow identification of individuals that have been infected with SARS-CoV-2 even if the infection was asymptomatic. To date, the vast majority of the serological tests for SARS-CoV-2-specific Abs are based on serum detection of Abs to either the viral spike glycoprotein (the major target for neutralizing Abs) or the viral nucleocapsid protein that is known to be highly immunogenic in other coronaviruses. Conceivably, exposure of Ags released from infected cells could stimulate Ab responses that might correlate with tissue damage and, hence, they may have some value as a prognostic indicator. We addressed whether other nonstructural viral proteins, not incorporated into the infectious viral particle, specifically the viral cysteine-like protease, might also be potent immunogens. Using ELISA tests, coating several SARS-CoV-2 proteins produced in vitro, we describe that COVID-19 patients make high titer IgG, IgM, and IgA Ab responses to the Cys-like protease from SARS-CoV-2, also known as 3CLpro or Mpro, and it can be used to identify individuals with positive serology against the coronavirus. Higher Ab titers in these assays associated with more-severe disease, and no cross-reactive Abs against prior betacoronavirus were found. Remarkably, IgG Abs specific for Mpro and other SARS-CoV-2 Ags can also be detected in saliva. In conclusion, Mpro is a potent Ag in infected patients that can be used in serological tests, and its detection in saliva could be the basis for a rapid, noninvasive test for COVID-19 seropositivity.

T1 mapping of the remote non-infarct myocardium for predicting adverse left ventricular remodeling following STEMI

Background

Adverse Left Ventricular (LV) remodeling (ALVR) following ST-segment Elevation Myocardial Infarction (STEMI) is the result of numerous mechanical, neurohormonal, micro and macrovascular factors, and remains a major clinical problem. Cardiac Magnetic Resonance (CMR) is a multimodality technique that provides comprehensive functional and tissue characterization of infarcted and non-infarcted myocardium. Whether changes in the extracellular matrix in the remote myocardium in patients following a STEMI are associated with adverse LV remodeling has been a topic of debate.

Aim

We explored the additive value of native T1 variation (ΔnT1) and derived-extracellular volume (ECV) fraction in the remote non-infarcted myocardium as predictors of adverse LV remodeling following STEMI.

Methods

A total of 99 subjects (83% male) with their first mechanically reperfused STEMI underwent CMR within 2 weeks and at 6 months, including T1 mapping prior and 15 to 20 minutes following a bolus of gadolinium (0.2 mmol/kg), with a MOLLI sequence. ECV and nT1 values were computed by averaging co-registered ROIs in three distinct segments in the remote non-infarcted myocardium.

Results

Baseline nT1 but not ECV correlated with infarct size (r=0.349, P&lt;0.001 and r=0.162, P=0.096 respectively). In addition, ΔnT1 but not ΔECV correlated with an increase in LV end-diastolic volume index (LVEDVi) (r=0.268, P&lt;0.01 and r=0.113, P=0.285).

ALVR, defined as Δ&gt;20% inLVEDVi, occurred in 21 cases, despite optimal medical therapy. Subjects with ALVR showed greater ΔnT1 (13.2±44.1 vs −5.2±30.2 ms, P&lt;0.05) but no significant differences in ΔECV (1.27±2.77 vs 0.72±2.45%, P=0.401). Also, subjects with ALVR were more likely hypertensive (67 vs 33%, P&lt;0.05), had more segments with microvascular obstruction (2.1±2.2 vs 0.8±1.7, P&lt;0.01) and lower baseline EF (39.8±8.8 vs 44.6±9.6%, P&lt;0.05). Infarct size was not significantly larger in ALVR subjects (20.7±13.4 vs 17.5±13.0% LV mass, P=0.322). A multivariate analysis including all these factors, showed the extent of microvascular obstruction (ExpoB: 1.35 [1.05–1.73], P=0.019) and remote ΔnT1 (ExpoB: 1.02 [1.00–1.03], P=0.026) to be the independent predictors of ALVR.

Conclusions

The nT1 variation in remote non-infarcted myocardium and the extent of microvascular obstruction are superior to ECV changes and infarct size in predicting ALVR following STEMI.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): Fundaciό La Maratό TV3 2015 30 31 32. Fondos FEDER

TERMINAL FLOWER-1/CENTRORADIALIS inhibits tuberisation via protein interaction with the tuberigen activation complex

Potato tuber formation is a secondary developmental programme by which cells in the subapical stolon region divide and radially expand to further differentiate into starch-accumulating parenchyma. Although some details of the molecular pathway that signals tuberisation are known, important gaps in our knowledge persist. Here, the role of a member of the TERMINAL FLOWER 1/CENTRORADIALIS gene family (termed StCEN) in the negative control of tuberisation is demonstrated for what is thought to be the first time. It is shown that reduced expression of StCEN accelerates tuber formation whereas transgenic lines overexpressing this gene display delayed tuberisation and reduced tuber yield. Protein-protein interaction studies (yeast two-hybrid and bimolecular fluorescence complementation) demonstrate that StCEN binds components of the recently described tuberigen activation complex. Using transient transactivation assays, we show that the StSP6A tuberisation signal is an activation target of the tuberigen activation complex, and that co-expression of StCEN blocks activation of the StSP6A gene by StFD-Like-1. Transcriptomic analysis of transgenic lines misexpressing StCEN identifies early transcriptional events in tuber formation. These results demonstrate that StCEN suppresses tuberisation by directly antagonising the function of StSP6A in stolons, identifying StCEN as a breeding marker to improve tuber initiation and yield through the selection of genotypes with reduced StCEN expression.

P1016Correlation between cardiac magnetic resonance-late gadolinium enhancement and electro-anatomical map for right atrium

Funding Acknowledgements

none

Background

 Electroanatomical map (EAM) detects areas of low voltage as a surrogated marker of fibrosis areas, being the reference technique for its detection. Cardiac magnetic resonance with Late Gadolinium enhancement (CMR-LGE) allows non-invasive detection of atrial fibrotic areas. CMR-LGE studies have focused on the left atrium since now.

Purpose

We need to validate this test to extend its use to the right atrium (RA), since it is involved in the arrhythmogenic substrate of several arrhythmias, and probably also in atrial fibrillation (AF).

Methods

 Prospective observational study. Fifteen patients undergoing a first AF ablation procedure were included. All patients had a pre-procedural LGE-CMR performed. The blood pool-normalized intensity signal (image intensity ratio-IIR) was calculated for the right atrial wall, and values projected in a shell. IIR values validated for the left atrium were used to identify dense and intermediate fibrosis, and healthy tissue (&gt;1.32, 1.2-1.32, &lt;1.2, respectively). During the procedure but before ablation, a point-by-point high density EA bipolar voltage map of RA was obtained with a multipolar catheter. Standard voltage thresholds of 0,1 mV and 0,5 mV were used to characterize fibrotic and healthy tissue in EAM. For each RA, the EAM was projected into the IIR shell, and the correlation between bipolar voltage and normalized IIR values for each shell point was quantified. Then, we also obtained its concordance (categorical variables) according to the label automatically assigned by EAM/CMR with the pre-set thresholds: healthy tissue/ intermediate fibrosis/dense fibrosis.

Results

 A total of 8,830 points were obtained, mean per patient 588 (± 509) points. A global weak negative correlation was found between the EA bipolar voltage map (EAM) and IIR (CMR) (r= -0.16, p &lt; 0.0001)(figure). LGE-CMR identified more healthy tissue than EAM (81.0% vs 60.6% respectively), then CMR underestimated the fibrotic tissue in RA. Finally, we analyzed the concordance and we obtained that the degree of accuracy between both measurements was 55.7%.

Conclusion

 There was an inverse correlation between the bipolar voltage EAM and IIR (CMR) of low grade but with statistical significance. CMR underestimated fibrotic tissue in RA with respect to its identification by EAM.

Abstract Figure. Correlation between bipolar voltage-IIR

P575Usefulness of late gadolinium enhancement cardiac magnetic resonance to predict appropriate therapies in implantable cardioverter defibrillator patients in primary prevention

Funding Acknowledgements

No funding acknowledgements

OnBehalf

VT and sudden cardiac death

Background

  The scar and the amount of border zone measured by late gadolinium enhancement cardiac magnetic resonance (LGE-CMR) has been proposed as an independent predictor of ventricular arrhythmias in patients with ischemic and non-ischemic cardiomyopathy. However, at the present time, the guidelines are based only on the ejection fraction to recommend an implantable cardioverter defibrillator (ICD) in primary prevention, and only a minority of these patients receive appropriate therapies. So, prevention needs to be improved.

Purpose

To identify predictors of appropriate therapies in patients with a primary prevention ICD using cardiac magnetic resonance imaging and a dedicated software (ADAS-3D) to characterize the scar.

Methods

All consecutive patients who underwent a LGE-MR prior to ICD implantation in primary prevention were prospectively included.  Clinical and cardiac imaging characteristics were collected. The myocardium was segmented with ADAS-3D software in 10 layers (from endocardium to epicardium). The scar, border zone, core and conducting channels were automatically measured in grams by the software.

Results

Since 2008 to 2017, 206 patients were included. Mean age was 67 +/- 28 years, 80% men, mean ejection fraction 26%+/-9, 52% with ischemic cardiomyopathy and 48% non-ischemic. The primary endpoint was appropriate therapies and/or sudden cardiac death (SCD). Median follow-up was 46,33 months.  46 patients (22%) reached the primary endpoint. Greater scar mass  (36,05 grams vs 21,5 grams; HR 1.04; 95% CI (1.03-1-05), p &lt;0.001), core mass (9,8 grams vs 5,6 grams; HR 1.06; 95% CI (1.04-1-09), p &lt;0.001),  border zone mass (26,2 grams vs 15,9 grams; HR 1.05; 95% CI (1.04-1-09), p &lt;0.001) and channel mass (3,0  grams vs 1,6 grams; HR 1.15 95% CI (1.06-1.25), p &lt;0.001) were associated with appropriate therapies and SCD.  A border zone mass &gt;5.3 grams was independently associated with the primary endpoint (HR: 4.77; 95% CI (1.15-19.73), p = 0.03).

Conclusions

 The amount of border zone, core and channel mass measured by LGE-MR and ADAS software are independent predictors of appropriate therapies and SCD in patients with ICD in primary prevention.

Abstract Figure. Scar characterization

P1129Bipolar voltage cut-off validation in electroanatomical voltage mapping to identify scar and conduction channels in ventricular tachycardia ablation: need for new cut-off in NICM

Background/Introduction

Substrate-guided techniques have changed the approach and results of ventricular tachycardia (VT) ablation and electroanatomical voltage mapping (EAVM) constitutes a diagnostic and therapeutic cornerstone in this field. In current practice normal myocardium is typically characterized by bipolar voltage &gt; 1.5 mV, dense scar &lt; 0.5 mV, and border zone (BZ) tissue by the range between 0.5 to 1.5 mV. Of note, evidence for these cut-off values has been derived in humans from small observational studies and in animals. Furthermore, some studies suggest that only the 60% of not transmural endocardial scars and the 35% of not endocardial scars are detected without any adjustment of these values. New voltage cut-off values are needed.

Purpose

The purpose of this study is to adjust voltage cut off in order to establish the threshold that more accurately define the pathological substrate in VT ablation. Additionally, predictors of usefulness of current thresholds are analyzed.

Methods

EAVM were created with CARTO3 System and Sensor-Force catheter (Navistar Smart-Touch and Pentaray). We delineated the conducting channels by analyzing the late potentials activation. Based on these channels we looked for the best cut-off values to detect these channels. We describe the baseline characteristics, the best cut-off values for border zone and scar core in our series and we analyzed the accuracy of the current established values to detect the arrhythmogenic VT substrate

Results

We investigated 51 patients (74,5% males; 41,2% ischemic cardiomyopathy, mean LVEF 38,6% +/-13,6) with sustained monomorphic VT submitted to ablation during 2016 and 2017. The range of the voltage adjustment was from 0,01-1 mV for core area and 0,2-6mV as maximum, with an average of 0,31-1,42mV. Using currently accepted bipolar voltage cut-off &lt;0.5 mV the core scar was correctly identified in 80,4% of patients: 90,4% in ischemic and 73,3% in NICM. Regarding BZ, using classical cut off (0.5-1.5mV) only 56,9 % of the cases were well identified: interestingly, accuracy was worse in NICM (46,6%) than in ischemic patients (71,4%) (p = 0,07).

Conclusions EAVM is very important to detect scar and channels in VT ablation, but several elements can affect it and recently the traditional voltage values have been questioned. Our study suggests how the threshold as currently applied in daily practice could be acceptable to detect the core scar area, but it has to be reconsidered in NICM, especially regarding the border zone. An evident trend (p = 0,07) suggests a better accuracy of current values to define VT substrate in ischemic patients than in NICM.

Abstract Figure. Channel Identification

Synchronization of developmental, molecular and metabolic aspects of source-sink interactions

Plants have evolved a multitude of strategies to adjust their growth according to external and internal signals. Interconnected metabolic and phytohormonal signalling networks allow adaption to changing environmental and developmental conditions and ensure the survival of species in fluctuating environments. In agricultural ecosystems, many of these adaptive responses are not required or may even limit crop yield, as they prevent plants from realizing their fullest potential. By lifting source and sink activities to their maximum, massive yield increases can be foreseen, potentially closing the future yield gap resulting from an increasing world population and the transition to a carbon-neutral economy. To do so, a better understanding of the interplay between metabolic and developmental processes is required. In the past, these processes have been tackled independently from each other, but coordinated efforts are required to understand the fine mechanics of source-sink relations and thus optimize crop yield. Here, we describe approaches to design high-yielding crop plants utilizing strategies derived from current metabolic concepts and our understanding of the molecular processes determining sink development.

474 Isolated pulmonary endocarditis

INTRODUCTION

Isolated pulmonary endocarditis is a rare entity, especially in patients without predisposing factors, being its current incidence less than 1% of the total cases of infectious endocarditis. This is due to the lower right heart pressures and a decrease of intravenous drug-consum, being most of the cases nowadays, related to congenital right-heart diseases or pacemakers and defibrillators implants.

CLINICAL CASE

A 35 year-old man, tobacco smoker and intravenous cocaine consumer since he was 25, was admitted to our Emergency Department for fever up to 40ºC, cough and dyspnea started three days before admission. In the anamnesis he refereed intravenous consum of cocaine and sharing of syringes the last week. On physical examination he was tachycardic and signs of heart right failure were present such as jugular ingurgitation and peripheral edema. No murmurs were heard. No respiratory failure was detected at any time. Blood test analysis showed high levels of protein C reactive and leukocytosis. Blood cultures were positive for S. aureus (OXA-S) in the first 24h. Chest X-ray (image 1) showed a necrotizing bilateral pneumonia that was confirmed with the presence of cavitated images in the pulmonary CT (image 2). Antibiotic treatment was started with daptomicine + cloxaciline. With the suspicion of right endocarditis a transthoracic echocardiography was performed, showing the presence of a big vegetation (4x1cm) on the pulmonary valve that caused moderate pulmonary insufficiency (images 3, 4). Neither tricuspid nor left side valves were involved. Biventricular function was conserved and hyperdynamic. Endocarditis diagnosis was definitive and due to the presence of multiple right embolisms and the big size of the vegetation, the patient underwent cardiac surgery. Intra-surgical finding demonstrated a big vegetation of almost 5 cm (image 5) depending of the posterior pulmonary valve that was removed; the posterior valve needed to be repaired. Posterior clinical evolution was correct without complications, completing 17 days of i.v. antibiotics (cloxaciline) before discharge.

CONCLUSIONS

Right endocarditis is a rapidly progressive disease due to the fact that staphylococcus are the most frequent microorganisms involved. Valvular destruction and secondary embolic phenomena are the rule. Tricuspid valve is involved most of the times being the isolated pulmonary valve affection very uncommon.

Abstract 474 Figure. CT, Echo and surgical images

Regulation of COP1 Function by Brassinosteroid Signaling

Small increases in temperature result in enhanced elongation of the hypocotyl and petioles and hyponastic growth, in an adaptive response directed to the cooling of the leaves and to protect the shoot meristem from the warm soil. This response, collectively termed as thermomorphogenesis, relies on the faster reversion of phyB Pfr at warmer temperatures, which leads to enhanced activity of the basic-helix-loop-helix PHYTOCHROME INTERACTING FACTOR 4 (PIF4). PIF4 acts as a molecular hub integrating light and temperature cues with endogenous hormonal signaling, and drives thermoresponsive growth by directly activating auxin synthesis and signaling genes. Growth promotion by PIF4 depends on brassinosteroid (BR) signaling, as indicated by the impaired thermoresponse of BR-defective mutants and the partial restoration of pifq thermoresponsive defects by brassinolide (BL) application. Also, phyB limits thermomorphogenic elongation through negative regulation of the E3 ubiquitin ligase COP1 that triggers nuclear degradation of multiple photomorphogenesis-promoting factors acting antagonistically to PIF4. COP1 is indeed observed to accumulate in the nucleus in darkness, or in response to warm temperatures, with constitutive photomorphogenic cop1 mutants failing to respond to temperature. Here we explored the role of BR signaling on COP1 function, by growing cop1 seedlings on BL or the inhibitor brassinazole (BRZ), under different light and temperature regimes. We show that weak cop1 alleles exhibit a hyposensitive response to BL. Furthermore, while cop1-6 mutants display as described a wild-type response to temperature in continuous darkness, this response is abolished by BRZ. Application of this inhibitor likewise suppressed temperature-induced COP1 nuclear accumulation in N. benthamiana leaves. Overall these results demonstrate that cop1-6 is not a temperature-conditional allele, but this mutation allows for a partially active protein which unveils a pivotal role of active BR signaling in the control of COP1 activity.

Identification of TIMING OF CAB EXPRESSION 1 as a temperature-sensitive negative regulator of tuberization in potato

For many potato cultivars, tuber yield is optimal at average daytime temperatures in the range 14-22 °C. Above this range, tuber yield is reduced for most cultivars. We previously reported that moderately elevated temperature increases steady-state expression of the core circadian clock gene TIMING OF CAB EXPRESSION 1 (StTOC1) in developing tubers, whereas expression of the StSP6A tuberization signal is reduced, along with tuber yield. In this study we provide evidence that StTOC1 links environmental signalling with potato tuberization by suppressing StSP6A autoactivation in the stolons. We show that transgenic lines silenced in StTOC1 expression exhibit enhanced StSP6A transcript levels and changes in gene expression in developing tubers that are indicative of an elevated sink strength. Nodal cuttings of StTOC1 antisense lines displayed increased tuber yields at moderately elevated temperatures, whereas tuber yield and StSP6A expression were reduced in StTOC1 overexpressor lines. Here we identify a number of StTOC1 binding partners and demonstrate that suppression of StSP6A expression is independent of StTOC1 complex formation with the potato homolog StPIF3. Down-regulation of StTOC1 thus provides a strategy to mitigate the effects of elevated temperature on tuber yield.

P3695Predicting adverse outcomes after TAVI procedure - a comparison of two CoreValve generations using real-life outcomes and patient-specific computer simulations

Background and aim

Post-procedure conduction abnormalities (CA) and paravalvular aortic regurgitation (PAR) continue to strain TAVI outcomes. Computer simulations, based on patient-specific anatomy, valve properties, and implantation position, have been validated for prediction of these complications. The new-generation CoreValve Evolut PRO has been shown to have lower levels of PAR and CA than previous generations. The aim was to compare clinical outcomes after Evolut Pro implantation in real-life with outcomes of virtual deployment of the same size, implantation depth adjusted CoreValve Evolut R.

Methods

Patients undergoing Evolut Pro implantation at a single centre were included into the study. Postoperative Doppler echocardiography was assessed to define PAR, the pre- and postoperative 12-lead ECGs for CA, and the postoperative angiograms to measure implantation depth based on annular plane distance from the non-coronary and left coronary aortic valve cusps. Preoperative multislice computed tomography was used to generate patient-specific models of the native aortic root. Implantation of the Evolut R valve and corresponding aortic root deformation was simulated using computational mechanics, whereas blood flow and level of PAR were predicted using computational fluid dynamics. Prediction of CA – new onset left bundle branch block or atrioventricular block type II or III -was based on calculations of contact pressure in a patient-specific region of the aortic root containing the AV conduction system (ROI). Outcomes were predicted in three implantation depth positions - high, medium, low – where the position closest to the real-life implantation depth was chosen for outcome comparisons.

Results

Study diagram is shown in Figure 1. Thirty-three patients (57% female, mean age 82±6 years old) underwent a TAVI intervention with an Evolut PRO valve. Evolut PRO implantation depths were, in general, closest to the lowest modeled Evolut R depth. Comparison demonstrated similar overall incidence of moderate-to-severe PAR. The Evolut R simulation predicted 18 patients without PAR and 2 with PAR. With the Evolute PRO, 1 of the 18 not predicted developed significant PAR, and 1 of the 2 predicted did not develop PAR. CA were notably higher with the Evolut R simulation, where CA were present in 9 out of 12 patients, as compared to the observed 5 out of 12 with the Evolut PRO.

Figure 1

Conclusion

Single-centre outcomes after Evolut Pro implantation in real-life showed a similar overall incidence of moderate-to-severe PAR and a lower incidence of conduction abnormalities as compared to the same size, implantation depth adjusted, patient-specific Evolut R modeled outcomes. As inferred from the results, computer simulations may have high clinical utility in supporting clinical decisions regarding valve choice in TAVI procedures.

Acknowledgement/Funding

Horizon 2020 European Commission Project H2020-MSCA-ITN-2016 (764738)

The origins and adaptation of European potatoes reconstructed from historical genomes

Potato, one of the most important staple crops, originates from the highlands of the equatorial Andes. There, potatoes propagate vegetatively via tubers under short days, constant throughout the year. After their introduction to Europe in the sixteenth century, potatoes adapted to a shorter growing season and to tuber formation under long days. Here, we traced the demographic and adaptive history of potato introduction to Europe. To this end, we sequenced 88 individuals that comprise landraces, modern cultivars and historical herbarium samples, including specimens collected by Darwin during the voyage of the Beagle. Our findings show that European potatoes collected during the period 1650-1750 were closely related to Andean landraces. After their introduction to Europe, potatoes admixed with Chilean genotypes. We identified candidate genes putatively involved in long-day pre-adaptation, and showed that the 1650-1750 European individuals were not long-day adapted through previously described allelic variants of the CYCLING DOF FACTOR1 gene. Such allelic variants were detected in Europe during the nineteenth century. Our study highlights the power of combining contemporary and historical genomes to understand the complex evolutionary history of crop adaptation to new environments.

Soil Salinity Limits Plant Shade Avoidance

Global food production is set to keep increasing despite a predicted decrease in total arable land [1]. To achieve higher production, denser planting will be required on increasingly degraded soils. When grown in dense stands, crops elongate and raise their leaves in an effort to reach sunlight, a process termed shade avoidance [2]. Shade is perceived by a reduction in the ratio of red (R) to far-red (FR) light and results in the stabilization of a class of transcription factors known as PHYTOCHROME INTERACTING FACTORS (PIFs) [3, 4]. PIFs activate the expression of auxin biosynthesis genes [4, 5] and enhance auxin sensitivity [6], which promotes cell-wall loosening and drives elongation growth. Despite our molecular understanding of shade-induced growth, little is known about how this developmental program is integrated with other environmental factors. Here, we demonstrate that low levels of NaCl in soil strongly impair the ability of plants to respond to shade. This block is dependent upon abscisic acid (ABA) signaling and the canonical ABA signaling pathway. Low R:FR light enhances brassinosteroid (BR) signaling through BRASSINOSTEROID SIGNALING KINASE 5 (BSK5) and leads to the activation of BRI1 EMS SUPPRESSOR 1 (BES1). ABA inhibits BSK5 upregulation and interferes with GSK3-like kinase inactivation by the BR pathway, thus leading to a suppression of BES1:PIF function. By demonstrating a link between light, ABA-, and BR-signaling pathways, this study provides an important step forward in our understanding of how multiple environmental cues are integrated into plant development.

PIF4-induced BR synthesis is critical to diurnal and thermomorphogenic growth

The Arabidopsis PIF4 and BES1/BZR1 transcription factors antagonize light signaling by facilitating co-activated expression of a large number of cell wall-loosening and auxin-related genes. While PIF4 directly activates expression of these targets, BES1 and BZR1 activity switch from a repressive to an activator function, depending on interaction with TOPLESS and other families of regulators including PIFs. However, the complexity of this regulation and its role in diurnal control of plant growth and brassinosteroid (BR) levels is little understood. We show by using a protein array that BES1, PIF4, and the BES1-PIF4 complex recognize different DNA elements, thus revealing a distinctive cis-regulatory code beneath BES1-repressive and PIF4 co-activation function. BES1 homodimers bind to conserved BRRE- and G-box elements in the BR biosynthetic promoters and inhibit their expression during the day, while elevated PIF4 competes for BES1 homodimer formation, resulting in de-repressed BR biosynthesis at dawn and in response to warmth. Our findings demonstrate a central role of PIF4 in BR synthesis activation, increased BR levels being essential to thermomorphogenic hypocotyl growth.

Convergent regulation of PIFs and the E3 ligase COP1/SPA1 mediates thermosensory hypocotyl elongation by plant phytochromes

The ability of plants to sense and integrate daily and seasonal changes in light and temperature and to adjust their growth and development accordingly, is critical to withstand severe weather oscillations in a year. While molecular mechanisms controlling light responses are relatively well established, those involved in the perception and response to temperature are just beginning to be understood. Phytochromes emerged as major temperature sensors; due to warmer temperatures accelerate the dark reversal reaction to the Pr inactive state. Downstream of phytochromes, the bHLH Phytochrome Interacting Factors, and in particular PIF4, act as central signaling hubs to growth coordination in response to light and temperature cues, and to the gibberellin and brassinosteroid pathways. Here we discuss recent findings showing that phytochromes control PIFs activity not only by signaling their destruction in the light, but by modulating transcriptional repression of these factors by the circadian clock. Together with this repression, phytochromes inactivate the COP1/SPA ubiquitin ligase, which negatively regulates light signaling through degradation of a large set of nuclear photomorphogenesis-promoting factors that suppress PIFs activity.

Transient Transactivation Studies in Nicotiana benthamiana Leaves

Transitory gene expression systems in Nicotiana benthamiana leaves, in combination with the use of gene silencing suppressors as the p19 or HC-pro proteins that allow for elevated levels of gene expression, have proven to be a highly versatile tool to analyze transcriptional function of DNA binding factors in the activated or repressed expression of their gene targets. This experimental setup uses Agrobacterium-mediated infection to deliver the various DNA constructs into the cell, and offers the advantage with respect to mesophyll protoplast transfection procedures that it entails a much easier protocol, in addition to preserving the intact leaf tissue, thus being more amenable to the study of wound and stress signaling pathways or to the functional analyses of regulators that respond to Ca+2 signatures. Furthermore, by using reporter constructs based on the LUCIFERASE (LUC) gene, which does not require a destructive determination assay, this expression system can be used to test for changes in gene activity over time or in response to various treatments, thus providing a comprehensive understanding of the signaling pathways that modulate activity of the expressed regulators and therefore their in vivo function in the control of the analyzed promoter.

Perception and signalling of light and temperature cues in plants

Light and temperature patterns are often correlated under natural plant growth conditions. In this review, we analyse the perception and signalling mechanisms shared by both these environmental cues and discuss the functional implications of their convergence to control plant growth. The first point of integration is the phytochrome B (phyB) receptor, which senses light and temperature. Downstream of phyB, the signalling core comprises two branches, one involving PHYTOCHROME INTERACTING FACTOR 4 (PIF4) and the other CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1) and ELONGATED HYPOCOTYL 5 (HY5). The dynamics of accumulation and/or localization of each of these core signalling components depend on light and temperature conditions. These pathways are connected through COP1, which enhances the activity of PIF4. The circadian clock modulates this circuit, since EARLY FLOWERING 3 (ELF3), an essential component of the evening complex (EC), represses expression of the PIF4 gene and PIF4 transcriptional activity. Phytochromes are probably not the only entry point of temperature into this network, but other sensors remain to be established. The sharing of mechanisms of action for two distinct environmental cues is to some extent unexpected, as it renders these responses mutually dependent. There are nonetheless many ecological contexts in which such a mutual influence could be beneficial.

TOPLESS mediates brassinosteroid control of shoot boundaries and root meristem development in Arabidopsis thaliana

The transcription factor BRI1-EMS-SUPRESSOR 1 (BES1) is a master regulator of brassinosteroid (BR)-regulated gene expression. BES1 together with BRASSINAZOLE-RESISTANT 1 (BZR1) drive activated or repressed expression of several genes, and have a prominent role in negative regulation of BR synthesis. Here, we report that BES1 interaction with TOPLESS (TPL), via its ERF-associated amphiphilic repression (EAR) motif, is essential for BES1-mediated control of organ boundary formation in the shoot apical meristem and the regulation of quiescent center (QC) cell division in roots. We show that TPL binds via BES1 to the promoters of the CUC3 and BRAVO targets and suppresses their expression. Ectopic expression of TPL leads to similar organ boundary defects and alterations in QC cell division rate to the bes1-d mutation, while bes1-d defects are suppressed by the dominant interfering protein encoded by tpl-1, with these effects respectively correlating with changes in CUC3 and BRAVO expression. Together, our data unveil a pivotal role of the co-repressor TPL in the shoot and root meristems, which relies on its interaction with BES1 and regulation of BES1 target gene expression.

Potato StCONSTANS-like1 Suppresses Storage Organ Formation by Directly Activating the FT-like StSP5G Repressor

The CONSTANS-FT pathway defines a core module for reproductive transition in both long-day (LD) and short-day (SD) plants. Changes in the transcriptional function of the CONSTANS (CO) protein have been proposed to mediate differential SD activation of FLOWERING LOCUS T (FT) orthologs in SD plants. Potato Andigena genotypes have an obligate SD requirement for tuber formation, and this photoperiodic response correlates with activation of the FT StSP6A gene in leaves. The potato StCOL1 factor represses expression of this mobile tuberization signal, but the control mechanism is poorly understood. Here, we analyzed StCOL1 diurnal oscillation and protein accumulation at different photoperiods and light wavelengths. We observed that the potato StCOL1 gene peaked at dawn and that, in contrast to the Arabidopsis AtCO homolog, the light receptor phyB is necessary for protein stabilization in the light. Reduced StCOL1 levels in RNAi lines strongly correlated with downregulated expression of an additional potato FT family member, StSP5G. Co-regulated StCOL1 and StSP5G expression suggested that StCOL1 activates this target directly rather than controlling StSP6A expression. By hybridization of a universal protein-binding microarray, we established that StCOL1 binds a TGTGGT element, and we found that immunoprecipitated StCOL1 protein fractions were enriched in StSP5G promoter fragments bearing this element. We show that StSP5G represses tuberization in LD conditions and that this FT-like homolog suppresses StSP6A gene expression. Rewiring StCOL1 transcriptional function from direct activation of the StSP6A inducer signal to the control of an FT-like repressor thus mediates the strict SD requirement of Andigena plants for tuberization.

Conserved function of FLOWERING LOCUS T (FT) homologues as signals for storage organ differentiation

Due to their high carbohydrate content and relative low farming demands, tuber-bearing species are an important contribution to human dietary needs in many climatic zones, and interest in these staple crops for processed food and other industrial uses is increasing. Over the past years we have seen remarkable advances in our understanding of the signalling mechanisms involved in the differentiation of these organs, partly aided by their conservation with the well-characterized photoperiodic control of flowering in Arabidopsis. Recent studies have led to the identification of members of the FT gene family as major component of the tuber-inducing signal and the characterization of circadian and photoperiodic components involved in the regulation of these genes. A relevant role of microRNAs in the control of storage organ formation has been established, and hormonal balance requirements similar to those controlling shoot branching were shown to be implicated in the activation of stolon meristem cells. Hence, the recent finding that FT controls branching through direct interaction with the TCP factors holds great promise for the identification of genes acting as FT signal integrators in the stolon.

ELF3-PIF4 interaction regulates plant growth independently of the Evening Complex

The circadian clock plays a pivotal role in the control of Arabidopsis hypocotyl elongation by regulating rhythmic expression of the bHLH factors PHYTOCHROME INTERACTING FACTOR 4 and 5 (PIF4 and 5). Coincidence of increased PIF4/PIF5 transcript levels with the dark period allows nuclear accumulation of these factors, and in short days it phases maximal hypocotyl growth at dawn. During early night, PIF4 and PIF5 transcription is repressed by the Evening Complex (EC) proteins EARLY FLOWERING3 (ELF3), EARLY FLOWERING4 (ELF4), and LUX ARRHYTHMO (LUX). While ELF3 has an essential role in EC complex assembly, several lines of evidence indicate that this protein controls plant growth via other mechanisms that are presently unknown. Here, we show that the ELF3 and PIF4 proteins interact in an EC-independent manner, and that this interaction prevents PIF4 from activating its transcriptional targets. We also show that PIF4 overexpression leads to ELF3 protein destabilization, and that this effect is mediated indirectly by negative feedback regulation of photoactive PHYTOCHROME B (phyB). Physical interaction of the phyB photoreceptor with ELF3 has been reported, but its functional relevance remains poorly understood. Our findings establish that phyB is needed for ELF3 accumulation in the light, most likely by competing for CONSTITUTIVELY PHOTOMORPHOGENIC1 (COP1)-mediated ubiquitination and the proteasomal degradation of ELF3. Our results explain the short hypocotyl phenotype of ELF3 overexpressors, despite their normal clock function, and provide a molecular framework for understanding how warm temperatures promote hypocotyl elongation and affect the endogenous clock.

Clinique de la pédopornographie sur Internet

Résumé non reçu.

BR-dependent phosphorylation modulates PIF4 transcriptional activity and shapes diurnal hypocotyl growth

Brassinosteroid (BR) and gibberellin (GA) hormone signaling cross-talk is critical to plant growth. Active BR signaling is essential for GA promotion of hypocotyl elongation in response to dark and elevated temperatures. Prat and colleagues show that light-regulated transcriptional regulator PIF4 is a substrate of BR signaling kinase BIN2, which marks factors for degradation. BR signaling suppresses PIF4 phosphorylation and stabilizes this regulator at night. The results uncover a regulatory mechanism that times hypocotyl elongation to the late night, before light activation signaling restricts PIF4 transcriptional activity.

Signaling by the hormones brassinosteroid (BR) and gibberellin (GA) is critical to normal plant growth and development and is required for hypocotyl elongation in response to dark and elevated temperatures. Active BR signaling is essential for GA promotion of hypocotyl growth and suppresses the dwarf phenotype of GA mutants. Cross-talk between these hormones occurs downstream from the DELLAs, as GA-induced destabilization of these GA signaling repressors is not affected by BRs. Here we show that the light-regulated PIF4 (phytochrome-interacting factor 4) factor is a phosphorylation target of the BR signaling kinase BRASSINOSTEROID-INSENSITIVE 2 (BIN2), which marks this transcriptional regulator for proteasome degradation. Expression of a mutated PIF41A protein lacking a conserved BIN2 phosphorylation consensus causes a severe elongated phenotype and strongly up-regulated expression of the gene targets. However, PIF41A is not able to suppress the dwarf phenotype of the bin2-1 mutant with constitutive activation of this kinase. PIFs were shown to be required for the constitutive BR response of bes1-D and bzr1-1D mutants, these factors acting in an interdependent manner to promote cell elongation. Here, we show that bes1-D seedlings are still repressed by the inhibitor BRZ in the light and that expression of the nonphosphorylatable PIF41A protein makes this mutant fully insensitive to brassinazole (BRZ). PIF41A is preferentially stabilized at dawn, coinciding with the diurnal time of maximal growth. These results uncover a main role of BRs in antagonizing light signaling by inhibiting BIN2-mediated destabilization of the PIF4 factor. This regulation plays a prevalent role in timing hypocotyl elongation to late night, before light activation of phytochrome B (PHYB) and accumulation of DELLAs restricts PIF4 transcriptional activity.

Ablation of frequent premature ventricular complex in an athlete

Premature ventricular complex are common findings in the exam of many athletes. There is no extensive scientific evidence in the management of this situation particularly when associated with borderline contractile function of the left ventricle. In this case report, we present a 35-year-old asymptomatic healthy athlete with high incidence (over 10,000 beats in 24 h) of premature ventricular complex and left ventricular dilatation with dysfunction, which persisted after a resting period of 6 months without training. We performed radiofrequency ablation of the premature ventricular complex focus. After 1-year follow-up, he was asymptomatic without arrhythmia and the left ventricle normalized its size and function as shown by echocardiogram and cardiac magnetic resonance.

PIFs get BRright: PHYTOCHROME INTERACTING FACTORs as integrators of light and hormonal signals

Light and temperature, in coordination with the endogenous clock and the hormones gibberellin (GA) and brassinosteroids (BRs), modulate plant growth and development by affecting the expression of multiple cell wall- and auxin-related genes. PHYTOCHROME INTERACTING FACTORS (PIFs) play a central role in the activation of these genes, the activity of these factors being regulated by the circadian clock and phytochrome-mediated protein destabilization. GA signaling is also integrated at the level of PIFs; the DELLA repressors are found to bind these factors and impair their DNA-binding ability. The recent finding that PIFs are co-activated by BES1 and BZR1 highlights a further role of these regulators in BR signal integration, and reveals that PIFs act in a concerted manner with the BR-related BES1/BZR1 factors to activate auxin synthesis and transport at the gene expression level, and synergistically activate several genes with a role in cell expansion. Auxins feed back into this growth regulatory module by inducing GA biosynthesis and BES1/BZR1 gene expression, in addition to directly regulating several of these growth pathway gene targets. An exciting challenge in the future will be to understand how this growth program is dynamically regulated in time and space to orchestrate differential organ expansion and to provide plants with adaptation flexibility.