Fertility loss in senescing Arabidopsis ovules is controlled by the maternal sporophyte via a NAC transcription factor triad.

Flowers have a species-specific fertile period during which pollination and fertilization have to occur to initiate seed and fruit development. Unpollinated flowers remain receptive for mere hours in some species, and up to several weeks in others before flower senescence terminates fertility. As such, floral longevity is a key trait subject to both natural selection and plant breeding. Within the flower, the life span of the ovule containing the female gametophyte is decisive for fertilization and the initiation of seed development. Here, we show that unfertilized ovules in Arabidopsis thaliana undergo a senescence program that generates morphological and molecular hallmarks of canonical programmed cell death processes in the sporophytically derived ovule integuments. Transcriptome profiling of isolated aging ovules revealed substantial transcriptomic reprogramming during ovule senescence, and identified up-regulated transcription factors as candidate regulators of these processes. Combined mutation of three most-up-regulated NAC (NAM, ATAF1/2, and CUC2) transcription factors, NAP/ANAC029, SHYG/ANAC047, and ORE1/ANAC092, caused a substantial delay in ovule senescence and an extension of fertility in Arabidopsis ovules. These results suggest that timing of ovule senescence and duration of gametophyte receptivity are subject to genetic regulation controlled by the maternal sporophyte.

KIL1 terminates fertility in maize by controlling silk senescence.

Plant flowers have a functional life span during which pollination and fertilization occur to ensure seed and fruit development. Once flower senescence is initiated, the potential to set seed or fruit is irrevocably lost. In maize, silk strands are the elongated floral stigmas that emerge from the husk-enveloped inflorescence to intercept airborne pollen. Here we show that KIRA1-LIKE1 (KIL1), an ortholog of the Arabidopsis NAC (NAM (NO APICAL MERISTEM), ATAF1/2 (Arabidopsis thaliana Activation Factor1 and 2) and CUC (CUP-SHAPED COTYLEDON 2)) transcription factor KIRA1, promotes senescence and programmed cell death (PCD) in the silk strand base, ending the window of accessibility for fertilization of the ovary. Loss of KIL1 function extends silk receptivity and thus strongly increases kernel yield following late pollination. This phenotype offers new opportunities for possibly improving yield stability in cereal crops. Moreover, despite diverging flower morphologies and the substantial evolutionary distance between Arabidopsis and maize, our data indicate remarkably similar principles in terminating floral receptivity by PCD, whose modulation offers the potential to be widely used in agriculture.

Neutrophils for Revascularization Require Activation of CCR6 and CCL20 by TNFα.

BACKGROUND: Activation of immune-inflammatory pathways involving TNFα (tumor necrosis factor alpha) signaling is critical for revascularization and peripheral muscle tissue repair after ischemic injury. However, mechanisms of TNFα-driven inflammatory cascades directing recruitment of proangiogenic immune cells to sites of ischemia are unknown. METHODS: Muscle tissue revascularization after permanent femoral artery ligation was monitored in mutant mice by laser Doppler imaging and light sheet fluorescence microscopy. TNFα-mediated signaling and the role of the CCL20 (C-C motif chemokine ligand 20)-CCR6 (C-C chemokine receptor 6) axis for formation of new vessels was studied in vitro and in vivo using bone marrow transplantation, flow cytometry, as well as biochemical and molecular biological techniques. RESULTS: TNFα-mediated activation of TNFR (tumor necrosis factor receptor) 1 but not TNFR2 was found to be required for postischemic muscle tissue revascularization. Bone marrow-derived CCR6+ neutrophil granulocytes were identified as a previously undescribed TNFα-induced population of proangiogenic neutrophils, characterized by increased expression of VEGFA (vascular endothelial growth factor A). Mechanistically, postischemic activation of TNFR1 induced expression of the CCL20 in vascular cells and promoted translocation of the CCL20 receptor CCR6 to the cell surface of neutrophils, essentially conditioning VEGFA-expressing proangiogenic neutrophils for CCL20-dependent recruitment to sites of ischemia. Moreover, impaired revascularization of ischemic peripheral muscle tissue in diabetic mice was associated with reduced numbers of proangiogenic neutrophils and diminished CCL20 expression. Administration of recombinant CCL20 enhanced recruitment of proangiogenic neutrophils and improved revascularization of diabetic ischemic skeletal muscles, which was sustained by sequential treatment with fluvastatin. CONCLUSIONS: We demonstrate that site-specific activation of the CCL20-CCR6 axis via TNFα recruits proangiogenic VEGFA-expressing neutrophils to sites of ischemic injury for initiation of muscle tissue revascularization. The findings provide an attractive option for tissue revascularization, particularly under diabetic conditions.

A peptide-mediated, multilateral molecular dialogue for the coordination of pollen wall formation.

The surface of pollen grains is reinforced by pollen wall components produced noncell autonomously by tapetum cells that surround developing pollen within the male floral organ, the anther. Here, we show that tapetum activity is regulated by the GASSHO (GSO) receptor-like kinase pathway, controlled by two sulfated peptides, CASPARIAN STRIP INTEGRITY FACTOR 3 (CIF3) and CIF4, the precursors of which are expressed in the tapetum itself. Coordination of tapetum activity with pollen grain development depends on the action of subtilases, including AtSBT5.4, which are produced stage specifically by developing pollen grains. Tapetum-derived CIF precursors are processed by subtilases, triggering GSO-dependent tapetum activation. We show that the GSO receptors act from the middle layer, a tissue surrounding the tapetum and developing pollen. Three concentrically organized cell types, therefore, cooperate to coordinate pollen wall deposition through a multilateral molecular dialogue.

Endosperm cell death: roles and regulation in angiosperms.

Double fertilization in angiosperms results in the formation of a second zygote, the fertilized endosperm. Unlike its embryo sibling, the endosperm is a transient structure that eventually undergoes developmentally controlled programmed cell death (PCD) at specific time points of seed development or germination. The nature of endosperm PCD exhibits a considerable diversity, both across different angiosperm taxa and within distinct endosperm tissues. In endosperm-less species, PCD might cause central cell degeneration as a mechanism preventing the formation of a fertilized endosperm. In most other angiosperms, embryo growth necessitates the elimination of surrounding endosperm cells. Nevertheless, complete elimination of the endosperm is rare and, in most cases, specific endosperm tissues persist. In mature seeds, these persisting cells may be dead, such as the starchy endosperm in cereals, or remain alive to die only during germination, like the cereal aleurone or the endosperm of castor beans. In this review, we explore current knowledge surrounding the cellular, molecular, and genetic aspects of endosperm PCD, and the influence environmental stresses have on PCD processes. Overall, this review provides an exhaustive overview of endosperm PCD processes in angiosperms, shedding light on its diverse mechanisms and its significance in seed development and seedling establishment.

Longer and better lives for patients with atrial fibrillation: the 9th AFNET/EHRA consensus conference.

AIMS: Recent trial data demonstrate beneficial effects of active rhythm management in patients with atrial fibrillation (AF) and support the concept that a low arrhythmia burden is associated with a low risk of AF-related complications. The aim of this document is to summarize the key outcomes of the 9th AFNET/EHRA Consensus Conference of the Atrial Fibrillation NETwork (AFNET) and the European Heart Rhythm Association (EHRA). METHODS AND RESULTS: Eighty-three international experts met in Münster for 2 days in September 2023. Key findings are as follows: (i) Active rhythm management should be part of the default initial treatment for all suitable patients with AF. (ii) Patients with device-detected AF have a low burden of AF and a low risk of stroke. Anticoagulation prevents some strokes and also increases major but non-lethal bleeding. (iii) More research is needed to improve stroke risk prediction in patients with AF, especially in those with a low AF burden. Biomolecules, genetics, and imaging can support this. (iv) The presence of AF should trigger systematic workup and comprehensive treatment of concomitant cardiovascular conditions. (v) Machine learning algorithms have been used to improve detection or likely development of AF. Cooperation between clinicians and data scientists is needed to leverage the potential of data science applications for patients with AF. CONCLUSIONS: Patients with AF and a low arrhythmia burden have a lower risk of stroke and other cardiovascular events than those with a high arrhythmia burden. Combining active rhythm control, anticoagulation, rate control, and therapy of concomitant cardiovascular conditions can improve the lives of patients with AF.

Surgical Ablation of Atrial Fibrillation in High-Risk Patients: Success versus Risk.

BACKGROUND: Surgical atrial ablation is evaluated by surgeons in relation to the estimated surgical risk. We analyze whether high-risk patients (HRPs) experience risk escalation by ablation procedures. METHODS: The CASE-Atrial Fibrillation (AF) registry is a prospective, multicenter, all-comers registry of atrial ablation in cardiac surgery. We analyzed the 1-year outcome regarding survival and rhythm endpoints of 1,000 consecutive patients according to the operative risk classification (EuroSCORE II ≤ 2 vs. >2). RESULTS: Higher NYHA (New York Heart Association) score, ischemic heart failure, status poststroke, renal insufficiency, chronic obstructive pulmonary disease, and diabetes mellitus were strongly represented in HRPs. HRPs exhibit more left ventricular ejection fraction < 40% (19.2 vs. 8.8%; p < 0.001) but identical left atrial diameter and left ventricular end-diastolic diameter compared with low-risk patients (LRPs). CHA2DS-Vasc-score (2.4 ± 1 vs. 3.6 ± 1.5; p < 0.001), sternotomies, combination surgeries, coronary artery bypass graft, and mitral valve procedures were increased in HRPs. LRPs underwent stand-alone ablations as well. Ablation energy did not differ. Left atrial appendage closure was performed in up to 86.1% (mainly cut-and-sew procedures). Mortality corresponded to the original risk class without an escalation that may be related to ablation, stroke rate, or myocardial infarction. A total of 60.6% of HRPs versus 75.1% of LRPs were discharged in sinus rhythm. Long-term EHRA (European Heart Rhythm Association) score symptoms were lower in HRPs. Repeated rhythm therapies were rare. Additional antiarrhythmics received a minority without group dependency. A total of 1.6 versus 4.1% of HRPs (p = 0.042) underwent long-term stroke; excess mortality was not observed. Anticoagulation remained common in HRPs. CONCLUSION: Surgical risk and long-term mortality are determined by the underlying disease. In HRPs, freedom from AF and symptom relief can be achieved. Preoperative risk scores should not lead to withholding an ablation procedure.

Transcriptomics at Maize Embryo/Endosperm Interfaces Identifies a Transcriptionally Distinct Endosperm Subdomain Adjacent to the Embryo Scutellum.

Seeds are complex biological systems comprising three genetically distinct tissues nested one inside another (embryo, endosperm, and maternal tissues). However, the complexity of the kernel makes it difficult to understand intercompartment interactions without access to spatially accurate information. Here, we took advantage of the large size of the maize (Zea mays) kernel to characterize genome-wide expression profiles of tissues at different embryo/endosperm interfaces. Our analysis identifies specific transcriptomic signatures in two interface tissues compared with whole seed compartments: the scutellar aleurone layer and the newly named endosperm adjacent to scutellum (EAS). The EAS, which appears around 9 d after pollination and persists for around 11 d, is confined to one to three endosperm cell layers adjacent to the embryonic scutellum. Its transcriptome is enriched in genes encoding transporters. The absence of the embryo in an embryo specific mutant can alter the expression pattern of EAS marker genes. The detection of cell death in some EAS cells together with an accumulation of crushed cell walls suggests that the EAS is a dynamic zone from which cell layers in contact with the embryo are regularly eliminated and to which additional endosperm cells are recruited as the embryo grows.

The German CArdioSurgEry Atrial Fibrillation Registry: In-Hospital Outcomes.

BACKGROUND: The aim of this study was to describe outcomes of patients undergoing surgical ablation for atrial fibrillation (AF) as either stand-alone or concomitant cardiosurgical procedures in Germany. METHODS: Patients with AF undergoing concomitant or stand-alone surgical ablation were included in the registry. Cardiac surgery centers across Germany were invited to participate and sought to enroll 1,000 consecutive patients. Data was obtained through electronic case report forms. The protocol mandated follow-up interviews at 1 year. RESULTS: Between January 2017 and April 2020, 17 centers enrolled 1,000 consecutive patients. Among concomitant surgical patients (n = 899), paroxysmal AF was reported in 55.4% patients. Epicardial radio frequency (RF) bilateral pulmonary vein isolation (PVI) with excision of the left atrial appendage (LAA) was the most common operative strategy. In the stand-alone cohort (n = 101), persistent AF forms were reported in 84.1% of patients. Moderate-to-severe symptoms were reported in 85.1%. Sixty-seven patients had previously underwent at least two failed catheter ablative procedures. Thoracoscopic epicardial RF bilateral PVI and completion of a "box-lesion" with LAA closure were frequently preformed. Major cardiac and cerebrovascular complications occurred in 38 patients (4.3%) in the concomitant group. No deaths were reported in the stand-alone group. At discharge, sinus rhythm was achieved in 88.1% of stand-alone and 63.4% concomitant patients. CONCLUSION: The CArdioSurgEry Atrial Fibrillation registry provides insights into surgical strategies for AF ablation in a considerable cohort across Germany. This in-hospital data demonstrates that concomitant and stand-alone ablation during cardiac surgery is safe and effective with low complication rates.

The German Cardiosurgery Atrial Fibrillation Registry: 1-Year Follow-up Outcomes.

OBJECTIVES: This study of German Cardiosurgery Atrial Fibrillation (CASE-AF) registry aims to describe the 1-year outcomes of patients undergoing ablative procedures for atrial fibrillation (AF) in a cardiosurgical setting. METHODS: Between January 2017 and April 2020, 17 German cardiosurgical units enrolled 1,000 consecutive patients undergoing concomitant or stand-alone ablation for AF. In-hospital and 1-year follow-up data were collected on web-based electronic case report forms. The protocol mandated telephone-based follow-up contact after 1 year. RESULTS: At 1-year follow-up (median, 14.5 months [12.6-18.2 months]), significant improvement (p < 0.0001) in baseline modified European Heart Rhythm Association Class I was reported in both concomitant and stand-alone patients. Follow-up examinations were completed in 97.9% of cases, and a sinus rhythm was reported in 60.2 and 63.6% of stand-alone and concomitant patients, respectively. Statistically significant factors determining late recurrence were female gender (p = 0.013), preoperative persistent AF (p < 0.0001), and presence of cardiac implantable electronic device (p = 0.011). All-cause mortality at 1 year was 1% (n = 1) in stand-alone patients and 6.7% (n = 58) in concomitant patients. CONCLUSION: Surgical ablation of AF is safe and provides satisfactory results at short-term follow-up, with significant improvement in patient symptoms. Adequate cardiac rhythm monitoring should be prioritized for higher quality data acquisition.

A stress-response-related inter-compartmental signalling pathway regulates embryonic cuticle integrity in Arabidopsis.

The embryonic cuticle is necessary for normal seed development and seedling establishment in Arabidopsis. Although mutants with defective embryonic cuticles have been identified, neither the deposition of cuticle material, nor its regulation, has been described during embryogenesis. Here we use electron microscopy, cuticle staining and permeability assays to show that cuticle deposition initiates de novo in patches on globular embryos. By combining these techniques with genetics and gene expression analysis, we show that successful patch coalescence to form a continuous cuticle requires a signalling involving the endosperm-specific subtilisin protease ALE1 and the receptor kinases GSO1 and GSO2, which are expressed in the developing embryonic epidermis. Transcriptome analysis shows that this pathway regulates stress-related gene expression in seeds. Consistent with these findings we show genetically, and through activity analysis, that the stress-associated MPK6 protein acts downstream of GSO1 and GSO2 in the developing embryo. We propose that a stress-related signalling pathway has been hijacked in some angiosperm seeds through the recruitment of endosperm-specific components. Our work reveals the presence of an inter-compartmental dialogue between the endosperm and embryo that ensures the formation of an intact and functional cuticle around the developing embryo through an "auto-immune" type interaction.

Does Preoperative Sinus Rhythm Influence Surgical Ablation's Perioperative Safety in Patients with Atrial Fibrillation?

BACKGROUND: Despite excellent data on lowering long-term stroke and all-cause mortality rates, currently, only 25-40% of atrial fibrillation (AF) patients undergo simultaneous surgical ablation therapy (SA) during cardiac surgery. Surgeon's fear exposing their patients to an additional, unjustified, and disproportionate risk when performing SA in AF patients presenting with sinus rhythm (SR) before surgery. To clarify the influence of preoperative SR before SA for AF, we conducted a subgroup analysis of the German Cardiosurgical Atrial Fibrillation (CASE-AF) register. METHODS: Between September 2016 and August 2020, 964 AF patients with an underlying cardiac disease were scheduled for surgery with SA and enrolled in the CASE-AF register. Data prospectively were collected and analyzed retrospectively. We divided the entire cohort into an SR-group (38.2%, N = 368) and an AF-group (61.8%, N = 596), based on preoperative heart rhythm. RESULTS: Over half of the patients were moderately affected by their AF, with no difference between the groups (European Heart Rhythm Association class ≥IIb: SR-group 54.2% versus AF-group 58.5%, P = .238). The AF-group had a higher preoperative EuroSCORE II (4.8 ± 8.0% versus 4.2 ± 6.3%, P = .014). In-hospital mortality (SR-group 0.8% versus AF-group 1.7%, P = .261), major perioperative adverse cardiac and cerebrovascular events (SR-group 2.7% versus AF-group 3.5%, P = .500), and the new pacemaker implantation rate (SR-group 6.0% versus AF-group 5.9%, P = .939) were low and showed and no group difference. Logistic regression analysis showed a protective effect for preoperative SR to perioperative complications in AF patients undergoing SA (odds ratio (OR) 0.72 (95% CI 0.52 - 0.998); P = .0485). CONCLUSIONS: Concomitant SA in AF patients presenting in SR before cardiac surgery is safe, has a low perioperative risk profile, and should be carried out with almost no exceptions.

Concomitant Activation of OSM and LIF Receptor by a Dual-Specific hlOSM Variant Confers Cardioprotection after Myocardial Infarction in Mice.

Oncostatin M (OSM) and leukemia inhibitory factor (LIF) signaling protects the heart after myocardial infarction (MI). In mice, oncostatin M receptor (OSMR) and leukemia inhibitory factor receptor (LIFR) are selectively activated by the respective cognate ligands while OSM activates both the OSMR and LIFR in humans, which prevents efficient translation of mouse data into potential clinical applications. We used an engineered human-like OSM (hlOSM) protein, capable to signal via both OSMR and LIFR, to evaluate beneficial effects on cardiomyocytes and hearts after MI in comparison to selective stimulation of either LIFR or OSMR. Cell viability assays, transcriptome and immunoblot analysis revealed increased survival of hypoxic cardiomyocytes by mLIF, mOSM and hlOSM stimulation, associated with increased activation of STAT3. Kinetic expression profiling of infarcted hearts further specified a transient increase of OSM and LIF during the early inflammatory phase of cardiac remodeling. A post-infarction delivery of hlOSM but not mOSM or mLIF within this time period combined with cardiac magnetic resonance imaging-based strain analysis uncovered a global cardioprotective effect on infarcted hearts. Our data conclusively suggest that a simultaneous and rapid activation of OSMR and LIFR after MI offers a therapeutic opportunity to preserve functional and structural integrity of the infarcted heart.