Various tomato cultivars display contrasting morphological and molecular responses to a chronic heat stress.

Climate change is one of the biggest threats that human society currently needs to face. Heat waves associated with global warming negatively affect plant growth and development and will increase in intensity and frequency in the coming years. Tomato is one of the most produced and consumed fruit in the world but remarkable yield losses occur every year due to the sensitivity of many cultivars to heat stress (HS). New insights into how tomato plants are responding to HS will contribute to the development of cultivars with high yields under harsh temperature conditions. In this study, the analysis of microsporogenesis and pollen germination rate of eleven tomato cultivars after exposure to a chronic HS revealed differences between genotypes. Pollen development was either delayed and/or desynchronized by HS depending on the cultivar considered. In addition, except for two, pollen germination was abolished by HS in all cultivars. The transcriptome of floral buds at two developmental stages (tetrad and pollen floral buds) of five cultivars revealed common and specific molecular responses implemented by tomato cultivars to cope with chronic HS. These data provide valuable insights into the diversity of the genetic response of floral buds from different cultivars to HS and may contribute to the development of future climate resilient tomato varieties.

Water column distribution of zooplanktonic size classes derived from in-situ plankton profilers: Potential use to contextualize contaminant loads in plankton.

Pollution is one of the main anthropogenic threats to marine ecosystems. Studies analysing the accumulation and transfer of contaminants in planktonic food webs tend to rely on samples collected in discrete water bodies. Here, we assessed the representativeness of measurements at the chlorophyll-a maximum layer during the MERITE-HIPPOCAMPE cruise for the entire water column by investigating the vertical distribution of particles and plankton obtained by in-situ optical profilers at nine stations across the Mediterranean Sea. We identified specific conditions where the interpretation of results from contaminant analyses can be improved by detailing plankton size structure and vertical distributions. First, the presence of higher than usual plankton concentrations can result in sampling issues that will affect biomass estimation within each size class and therefore bias our understanding of the contaminant dynamics. Secondly, the presence of an unsampled water layer with high zooplankton biomass might imply non-resolved contaminant pathways along the trophic structure. This study lays the basis for optimizing sampling strategy in contaminant studies.

Feature tracking cardiovascular magnetic resonance reveals recovery of atrial function after acute myocarditis.

Follow-up after acute myocarditis is important to detect persisting myocardial dysfunction. However, recovery of atrial function has not been evaluated after acute myocarditis so far. Thirty-five patients with strictly defined acute myocarditis underwent cardiovascular magnetic resonance (CMR, 1.5 T) in the acute stage at baseline (BL) and at 3 months follow-up (FU). The study population included 13 patients with biopsy-proven "cardiomyopathy-like" myocarditis (CLM) and 22 patients with "infarct-like" (ILM) clinical presentation. CMR feature tracking (FT) was performed on conventional cine SSFP sequences. Median LA-GLS increased from 33.2 (14.5; 39.2) at BL to 37.0% (25.2; 44.1, P = 0.0018) at FU in the entire study population. Median LA-GLS also increased from 36.7 (26.5; 42.3) at BL to 41.3% (34.5; 44.8, P = 0.0262) at FU in the ILM subgroup and from 11.3 (6.4; 21.1) at BL to 21.4% (14.2; 30.7, P = 0.0186) at FU in the CLM subgroup. Median RA-GLS significantly increased from BL with 30.8 (22.5; 37.0) to FU with 33.7% (26.8; 45.4, P = 0.0027) in the entire study population. Median RA-GLS also significantly increased from 32.7 (25.8; 41.0) at BL to 35.8% (27.7; 48.0, P = 0.0495) at FU in the ILM subgroup and from 22.8 (13.1; 33.9) at BL to 31.0% (26.0; 40.8, P = 0.0266) at FU in the CLM subgroup. Our findings demonstrate recovery of LA and RA function by CMR-FT strain analyses in patients after acute myocarditis independent from clinical presentation. Monitoring of atrial strain could be an important tool for an individual assessment of healing after acute myocarditis.

Human factor associations with safety events in radiation therapy.

BACKGROUND AND PURPOSE: Incident learning can reveal important opportunities for safety improvement, yet learning from error is challenged by a number of human factors. In this study, incident learning reports have been analyzed with the human factors analysis classification system (HFACS) to uncover predictive patterns of human contributing factors. MATERIALS AND METHODS: Sixteen hundred reports from the Safety in Radiation Oncology incident learning system were filtered for inclusion ultimately yielding 141 reports. A radiotherapy-specific error type was assigned to each event as were all reported human contributing factors. An analysis of associations between human contributing factors and error types was performed. RESULTS: Multiple associations between human factors were found. Relationships between leadership and risk were demonstrated with supervision failures. Skill-based errors (those done without much thought while performing familiar tasks) were found to pose a significant safety risk to the treatment planning process. Errors made during quality assurance (QA) activities were associated with decision-based errors which indicate lacking knowledge or skills. CONCLUSION: An application of the HFACS to incident learning reports revealed relationships between human contributing factors and radiotherapy errors. Safety improvement efforts should include supervisory influences as they affect risk and error. An association between skill-based and treatment planning errors showed a need for more mindfulness in this increasingly automated process. An association between decision and QA errors revealed a need for improved education in this area. These and other findings can be used to strategically advance safety.

[Extreme hypofractionated radiation therapy for pancreatic cancer]. / Radiothérapie hypofractionnée extrême du cancer du pancréas.

Pancreatic cancer has poor prognosis and a continuously growing incidence. By 2030, it should become the second cause of death by cancer worldwide and in France. The only curative treatment is surgery that is achievable in only 20% of patients at the time of initial diagnosis, with a high rate of incomplete resection. Neoadjuvant treatments using chemotherapy with or without radiotherapy are more often admitted to play an important role by selecting non-progressing cases who will benefit from surgery, by increasing the number of complete resection, and by making locally advanced and borderline tumours accessible to resection. However, the role of radiotherapy is still debated. Because of its dosimetric advantages, its short total duration, and its good tolerance with reduced volumes of irradiation, stereotactic radiotherapy has been largely studied. Compared to chemoradiotherapy, this technique could improve the therapeutic index helping to preserve the general status of patients in order to give them access to secondary surgery. It remains a promising technique still under evaluation, to be delivered ideally, as part of a clinical trial, or within an experimented team.

Molecular identification of fungi microfossils in a Neoproterozoic shale rock.

Precambrian fossils of fungi are sparse, and the knowledge of their early evolution and the role they played in the colonization of land surface are limited. Here, we report the discovery of fungi fossils in a 810 to 715 million year old dolomitic shale from the Mbuji-Mayi Supergroup, Democratic Republic of Congo. Syngenetically preserved in a transitional, subaerially exposed paleoenvironment, these carbonaceous filaments of ~5 µm in width exhibit low-frequency septation (pseudosepta) and high-angle branching that can form dense interconnected mycelium-like structures. Using an array of microscopic (SEM, TEM, and confocal laser scanning fluorescence microscopy) and spectroscopic techniques (Raman, FTIR, and XANES), we demonstrated the presence of vestigial chitin in these fossil filaments and document the eukaryotic nature of their precursor. Based on those combined evidences, these fossil filaments and mycelium-like structures are identified as remnants of fungal networks and represent the oldest, molecularly identified remains of Fungi.

Induced ovule-to-flower switch by interfering with SlIMA activity in tomato.

The INHIBITOR OF MERISTEM ACTIVITY in tomato (SlIMA) and MINI ZINC FINGER 2 in Arabidopsis (AtMIF2), two members of the MINI ZINC FINGER family (MIF), are involved in the regulation of flower and ovule development. MIF proteins possess a unique non-canonical zinc-finger domain that confers the capacity to interact with other protein partners. The characterization of SlIMA and AtMIF2 gain- and loss-of-function transgenic lines in Solanum lycopersicum and Arabidopsis thaliana respectively, allowed the demonstration of their conserved functional role in the termination of floral stem cell maintenance. During early floral development, the expression of SlIMA and AtMIF2 is induced by the MADS-Box transcription factor AGAMOUS (AG). Then, SlIMA or AtMIF2 protein recruits the C2H2 zinc finger KNUCKLES (KNU), in a transcriptional repressor complex together with TOPLESS (TPL) and HISTONE DEACETYLASE19 (HDA19). This complex binds to the WUSCHEL (WUS) locus leading to its repression. To further characterize the role of these interactions in flower development, we have investigated the effects of a dominant negative form of SlIMA, SlIMAch that leads to spectacular phenotypes, including ovule conversion into a floral meristem.

Salvage brachytherapy as a modern reirradiation technique for local cancer failure: The Phoenix is reborn from its ashes.

The treatment of local recurrence of a previously irradiated cancer or a second cancer arising in-field remains challenging. Ultimately, the objective of salvage therapy is to control disease while ensuring minimal collateral damage, thereby optimizing both cancer and toxicity outcomes. Reirradiation has historically been associated with unacceptable toxicity and a limited benefit. Brachytherapy offers the best dose distribution and a high radiation dose to the target volume while better protecting surrounding previously irradiated healthy tissues. The management of local cancer recurrence in irradiated areas should be planned through multidisciplinary discussions and patients should be selected carefully. This overview of the literature describes brachytherapy as a reirradiation treatment in local recurrences of previously irradiated prostate, breast, head and neck and rectal cancers, or second primary cancers occurring in-field. For these cancers, the prognosis and therapeutic challenges are quite different and depend on the type of primary cancer. However, current data confirm that brachytherapy reirradiation is feasible and has acceptable toxicity.

[An assessment of the direct costs of healthcare for victims of sexual assaults in hospital emergency units]. / Évaluation des coûts directs de la prise en charge en urgence d'une victime de violences sexuelles.

BACKGROUND: The Forensic medicine reform in 2011 enabled the development of forensic units specialized in multidisciplinary care of victims of criminal offences. Thanks to an annual budgetary allocation, the Ministry of Justice handles the financing of judicial acts, while the health care facilities assume the medical, psychological and social aspects. The objective of this study was to determine the direct costs of medical care provided to rape victims (such as defined in the article 222-23 of the Penal Code) in order to see how its funding could be reconsidered to prevent any additional cost that could be caused by non-sufficient medical, psychological and social care. Furthermore, this first assessment may serve as a basis for further reflection on creating other medical judicial units but also for reviewing existing structures. METHODS: The direct costs for medical care of a recent rape victim (<48hours) was quantified by including staff and consumables costs, treatments, biological tests and other expenses. RESULTS: The overall time for the entire medical care procedure was approximately three hours, for an overall cost of 673.92€, of which 41.5 % (279.90€) was paid by the Ministry of Justice. The medical, psychological and social aspects stood for the major expenditure items (394.02€), attributable mainly to the biological screening tests for sexually transmissible infections (STIs). CONCLUSION: These frequent situations require the convergence of human and material needs with a financial burden shared between the Ministry of Justice and health establishments. Authors suggest that in the annual hospital budgetary allocation allotted by the Ministry of Justice, the care of victims of sexual assault be based on the rate of day hospitalization "Medicine, medical specialties part time day or night common regime", allowing to provide optimal multidisciplinary care, which lessens the risks of complications and reduces the global cost created by these situations.

Shoulder patient-specific guide: First experience in 10 patients indicates room for improvement.

BACKGROUND: Implantation of the glenoid component of a total shoulder prosthesis can be facilitated by using a patient-specific guide (PSG) designed to ensure replication of the preoperatively planned position. The objective of this study was to assess the reliability and accuracy of a PSG in replicating the planned glenoid component position during total shoulder arthroplasty (TSA). HYPOTHESIS: Additional criteria should be used for 3D preoperative planning and PSG design to further improve the accuracy of glenoid component positioning. MATERIAL AND METHODS: We studied 10 patients who underwent TSA with use of a PSG to position the glenoid component after preoperative 3D planning. Postoperative glenoid version and tilt were measured and compared to the planned values. We also used new criteria to assess implant rotation and global 3D position, as well as accuracy of the 3D pilot hole for the glenoid guide-pin. RESULTS: Mean errors in glenoid position were -1.7°±4.4° for version, -0.4°±4.9° for tilt, and 6.0°±13.5° for rotation. Mean difference in global orientation of the glenoid implant versus the planned value was 4.9°±2.5°. Mean 3D discrepancy in glenoid pilot hole position was 2.9±0.5mm; the discrepancy was greater in the mediolateral direction (1.9±0.9mm) than in the supero-inferior (1.1±1.2mm) and antero-posterior (0.8±1.2mm) directions. DISCUSSION: The poor performance of the PSG in controlling rotation and reaming may explain the difference in global glenoid position compared to the planned value. Improvements in PSG design to incorporate these two parameters deserve consideration. LEVEL OF EVIDENCE: II, prospective cohort study.

[End-of-life debate: Citizen's point of view about deep and continuous sedation]. / Débat sur la fin de vie en France : regard du citoyen sur la sédation profonde et continue.

INTRODUCTION: Sedation in palliative care meets a precise definition and corresponds to a medical practice. We assessed the comprehension of this practice by the French population. METHOD: In 2015, citizen expressed their views on the Claeys-Leonetti bill by means of a consultative forum made available on the Internet site of the National Assembly. The content of the messages filed, regarding the right to deep and continuous sedation until death was analyzed using the ALCESTE textual data analysis software, supplemented by a thematic analysis in order to identify the perception that Internet users had of this practice. RESULTS: Among the 1819 Internet users who participated in the forum, 67 expressed their views as Health professionals, 25 of whom were directly involved in palliative care, as well as 10 sick persons. Analysis with the ALCESTE software highlighted two classes of statements. The first dealing with deep and continuous sedation, reflecting the specificity of the discourse of the Internet users. The second one consisted of textual units in which the modal verbs were dominant and overrepresented, thus providing information on the participants' perceptions. The thematic analysis highlighted four themes: death, intent, treatment and fear. CONCLUSION: Deep and continuous sedation is perceived as a euthanasic practice or raises fear of such a drift. Provision of extended and accurate information to the population and health professionals is essential to ensure that this new model of sedation is integrated into the care of the terminally ill patients and their families.

Endoscopic ulnar nerve release at the elbow: Indications and outcomes.

BACKGROUND: Ulnar nerve entrapment at the elbow is the second most common nerve entrapment syndrome at the upper limp, after carpal tunnel syndrome. Many surgeons feel that ulnar nerve instability contra-indicates endoscopic nerve release. Published studies, however, found no evidence that pre-operative or intra-operative ulnar nerve instability adversely affected clinical outcomes. The objective of this prospective study was to define the indications and describe the outcomes of endoscopic ulnar nerve release at the elbow. HYPOTHESIS: Endoscopic ulnar nerve release at the elbow is a valid option even in patients with ulnar nerve instability and regardless of the severity of the compression. MATERIAL AND METHODS: We conducted a prospective single-centre study of patients scheduled for surgery based on clinical and electromyographic manifestations of ulnar nerve entrapment at the elbow. Ulnar nerve instability (incomplete dislocation, i.e., Childress A) before or during surgery was not a contra-indication to the procedure. The patients were re-evaluated 12 months after surgery. RESULTS: Seventeen patients were included in the statistical analysis. The modified Bishop's score indicated excellent or good outcomes in 15 (88%) patients (excellent in 4 and good in 11) and a fair outcome in 2 patients. Functional outcomes were not associated with the presence of ulnar nerve instability before surgery. DISCUSSION: We elected to include patients with Childress A ulnar nerve instability. Clinical outcomes in these patients were similar to those in patients without ulnar nerve instability. LEVEL OF EVIDENCE: IV, open prospective study of treatment outcomes.

The respiratory DC/macrophage network at steady-state and upon influenza infection in the swine biomedical model.

Human and mouse respiratory tracts show anatomical and physiological differences, which will benefit from alternative experimental models for studying many respiratory diseases. Pig has been recognized as a valuable biomedical model, in particular for lung transplantation or pathologies such as cystic fibrosis and influenza infection. However, there is a lack of knowledge about the porcine respiratory immune system. Here we segregated and studied six populations of pig lung dendritic cells (DCs)/macrophages (Mθs) as follows: conventional DCs (cDC) 1 and cDC2, inflammatory monocyte-derived DCs (moDCs), monocyte-derived Mθs, and interstitial and alveolar Mθs. The three DC subsets present migratory and naive T-cell stimulation capacities. As observed in human and mice, porcine cDC1 and cDC2 were able to induce T-helper (Th)1 and Th2 responses, respectively. Interestingly, porcine moDCs increased in the lung upon influenza infection, as observed in the mouse model. Pig cDC2 shared some characteristics observed in human but not in mice, such as the expression of FCɛRIα and Langerin, and an intra-epithelial localization. This work, by unraveling the extended similarities of the porcine and human lung DC/Mθ networks, highlights the relevance of pig, both as an exploratory model of DC/Mθ functions and as a model for human inflammatory lung pathologies.

Verneuil's disease, innate immunity and vitamin D: a pilot study.

BACKGROUND: Verneuil's disease is a chronic inflammatory skin disease of the follicles in apocrine glands rich area of the skin (axillary, inguinal, anogenital) and is associated with a deficient skin innate immunity. It is characterized by the occurrence of nodules, abscesses, fistulas, scars. Recently, vitamin D has been shown to stimulate skin innate immunity. OBJECTIVE: The primary objective of the study was to assess whether Verneuil's disease was associated with vitamin D deficiency. The secondary objective was to determine whether vitamin D supplementation could improve inflammatory lesions. METHODS: First, 25(OH) vitamin D3 serum levels in patients with Verneuil's disease followed at Nantes University Hospital were compared to those of healthy donors from the French Blood Bank. Then, a pilot study was conducted in 14 patients supplemented with vitamin D according to their vitamin D level at baseline at months 3 and 6. The endpoints at 6 months were decreased by at least 20% in the number of nodules and in the frequency of flare-ups. RESULTS: Twenty-two patients (100%) had vitamin D deficiency (level <30 ng/mL) of whom 36% were severely deficient (level <10 ng/mL), having correlation with the disease severity (P = 0.03268) vs. 20 controls with vitamin D deficiency (91%) of whom 14% were severely deficient. In 14 patients, the supplementation significantly decreased the number of nodules at 6 months (P = 0.01133), and the endpoints were achieved in 79% of these patients. A correlation between the therapeutic success and the importance of the increase in vitamin D level after supplementation was observed (P = 0.01099). CONCLUSION: Our study shows that Verneuil's disease is associated with a major vitamin D deficiency, correlated with the disease severity. It suggests that vitamin D could significantly improve the inflammatory nodules, probably by stimulating the skin innate immunity. A larger randomized study is needed to confirm these findings.

Breaking of non-Newtonian character in flows through a porous medium.

From NMR measurements we show that the velocity field of a yield stress fluid flowing through a disordered well-connected porous medium is very close to that for a Newtonian fluid. In particular, it is shown that no arrested regions exist even at very low velocities, for which the solid regime is expected to be dominant. This suggests that these results obtained for strongly nonlinear fluid can be extrapolated to any nonlinear fluid. We deduce a generalized form of Darcy's law for such materials and provide insight into the physical origin of the coefficients involved in this expression, which are shown to be moments of the second invariant of the strain rate tensor.

Velocity distributions in confined flows of some complex fluids: sequence, sample and hardware issues.

The present work addresses the problem of using Pulsed Field Gradient (PFG) experiments to measure velocity probability density functions and/or distributions in restricted flows, without being subjected to the blurring due to diffusive molecular motions. It especially focuses on two important classes of complex yield-stress fluids, i.e. water based colloidal suspensions or polymeric gels, and concentrated emulsions. Taking into account the many constraints owing to fluid diffusive properties, flow rate, hardware characteristics and pore size, it is found that the existence of suitable and optimised sequence parameters can be discussed in a graphical way. To do so, it also shown that Murday and Cotts formula describing diffusion inside emulsion droplets can be efficiently approximated by means of a set of asymptotic expressions. Different tuning regimes are identified for both kind of fluids, highlighting the influence of each of the various constraints on measuring possibilities. A method is given to build quantitative diagrams indicating pore sizes and flow rates allowing pure velocity assessment for a given fluid and Nuclear Magnetic Resonance (NMR) hardware. Measurements are found to be mainly constrained by fluid self-diffusivity and microstructure at low flow rates, and hardware characteristics at high flow rates. Although high gradient strengths can be made necessary to decrease achievable velocities and pore sizes in some specific cases, low gradient systems turn out suitable in many situations thanks to optimised sequence tuning. Due to their larger size, the latter also appear to offer the widest variety of workable experimental conditions. The use of these results is finally exemplified on the practical case of an emulsion flow in a model porous system.

Air breathing in Magadi tilapia Alcolapia grahami, under normoxic and hyperoxic conditions, and the association with sunlight and reactive oxygen species.

Observations of the Magadi tilapia Alcolapia grahami in hot, highly alkaline Lake Magadi revealed that they air breathe not only during hypoxia, as described previously, but also during normoxia and hyperoxia. Air breathing under these latter conditions occurred within distinct groupings of fish (pods) and involved only a small proportion of the population. Air breathing properties (duration and frequency) were quantified from video footage. Air breathing within the population followed a diel pattern with the maximum extent of pod formation occurring in early afternoon. High levels of reactive oxygen species (ROS) in the water may be an irritant that encourages the air-breathing behaviour. The diel pattern of air breathing in the field and in experiments followed the diel pattern of ROS concentrations in the water which are amongst the highest reported in the literature (maximum daytime values of 2.53 ­ 8.10 µM H2O2). Interlamellar cell masses (ILCM) occurred between the gill lamellae of fish from the lagoon with highest ROS and highest oxygen levels, while fish from a normoxic lagoon with one third the ROS had little or no ILCM. This is the first record of air breathing in a facultative air-breathing fish in hyperoxic conditions and the first record of an ILCM in a cichlid species.

Systematic screening for PRKAR1A gene rearrangement in Carney complex: identification and functional characterization of a new in-frame deletion.

BACKGROUND: Point mutations of the PRKAR1A gene are a genetic cause of Carney complex (CNC) and primary pigmented nodular adrenocortical disease (PPNAD), but in 30% of the patients no mutation is detected. OBJECTIVE: Set up a routine-based technique for systematic detection of large deletions or duplications of this gene and functionally characterize these mutations. METHODS: Multiplex ligation-dependent probe amplification (MLPA) of the 12 exons of the PRKAR1A gene was validated and used to detect large rearrangements in 13 typical CNC and 39 confirmed or putative PPNAD without any mutations of the gene. An in-frame deletion was characterized by western blot and bioluminescence resonant energy transfer technique for its interaction with the catalytic subunit. RESULTS: MLPA allowed identification of exons 3-6 deletion in three patients of a family with typical CNC. The truncated protein is expressed, but rapidly degraded, and does not interact with the protein kinase A catalytic subunit. CONCLUSIONS: MLPA is a powerful technique that may be used following the lack of mutations detected by direct sequencing in patients with bona fide CNC or PPNAD. We report here one such new deletion, as an example. However, these gene defects are not a frequent cause of CNC or PPNAD.

Morphological evaluation of spermatogenesis in Lake Magadi tilapia (Alcolapia grahami): a fish living on the edge.

Spermatogenesis in Lake Magadi tilapia (Alcolapia grahami), a cichlid fish endemic to the highly alkaline and saline Lake Magadi in Kenya, was evaluated using light and transmission electron microscopy. Spermatogenesis, typified by its three major phases (spermatocytogenesis, meiosis and spermiogenesis), was demonstrated by the presence of maturational spermatogenic cells namely spermatogonia, spermatocytes, spermatids and spermatozoa. Primary spermatogonia, the largest of all the germ cells, underwent a series of mitotic divisions producing primary spermatocytes, which then entered two consecutive meiotic divisions to produce secondary spermatocytes and spermatids. Spermatids, in turn, passed through three structurally distinct developmental stages typical of type-I spermiogenesis to yield typical primitive anacrosomal spermatozoa of the externally fertilizing type (aquasperm). The spermatozoon of this fish exhibited a spheroidal head with the nucleus containing highly electron-dense chromatin globules, a midpiece containing ten ovoid mitochondria arranged in two rows and a flagellum formed by the typical 9 + 2 microtubule axoneme. In addition, the midpiece, with no cytoplasmic sheath, appeared to end blindly distally in a lobe-like pattern around the flagellum; a feature that was unique and considered adaptive for the spermatozoon of this species to the harsh external environment. These observations show that the testis of A. grahami often undergoes active spermatogenesis despite the harsh environmental conditions to which it is exposed on a daily basis within the lake. Further, the spermiogenic features and spermatozoal ultrastructure appear to be characteristic of Cichlidae and, therefore, may be of phylogenetic significance.

Oligomerization paths of the nucleoprotein of influenza A virus.

The influenza viruses contain a segmented, negative strand RNA genome. Each RNA segment is covered by multiple copies of the nucleoprotein (NP) and is associated with the polymerase complex into ribonucleoprotein (RNP) particles. Despite its importance in the virus life cycle, the interactions between the NP and the genome are not well understood. Here, we studied the assembly process of NP-RNA oligomers and analyzed how the oligomeric/monomeric status of RNA-free NP affects RNA binding and oligomerization. Recombinant wild-type NP purified in low salt concentrations and a derived mutant engineered for oligomerization deficiency (R416A) were mainly monomeric in RNA-free solutions as shown by biochemical and electron microscopy techniques. NP monomer formed with RNA a fast 1/1 complex characterized by surface plasmon resonance. In a subsequent and slow process that depended on the RNA length, oligomerization of NP was mediated by RNA binding. In contrast, preparations of wild-type NP purified in high salt concentrations as well as mutant Y148A engineered for deficiency in nucleic acid binding were partly or totally oligomeric in RNA-free solutions. These trimer/tetramer NP oligomers bind directly as oligomers to RNA with a higher affinity than that of the monomers. Both oligomerization routes we characterized could be exploited by cellular or viral factors to modulate or control viral RNA encapsidation by NP.