Microbiome changes through the ontogeny of the marine sponge Crambe crambe.

BACKGROUND: Poriferans (sponges) are highly adaptable organisms that can thrive in diverse marine and freshwater environments due, in part, to their close associations with internal microbial communities. This sponge microbiome can be acquired from the surrounding environment (horizontal acquisition) or obtained from the parents during the reproductive process through a variety of mechanisms (vertical transfer), typically resulting in the presence of symbiotic microbes throughout all stages of sponge development. How and to what extent the different components of the microbiome are transferred to the developmental stages remain poorly understood. Here, we investigated the microbiome composition of a common, low-microbial-abundance, Atlantic-Mediterranean sponge, Crambe crambe, throughout its ontogeny, including adult individuals, brooded larvae, lecithotrophic free-swimming larvae, newly settled juveniles still lacking osculum, and juveniles with a functional osculum for filter feeding. RESULTS: Using 16S rRNA gene analysis, we detected distinct microbiome compositions in each ontogenetic stage, with variations in composition, relative abundance, and diversity of microbial species. However, a particular dominant symbiont, Candidatus Beroebacter blanensis, previously described as the main symbiont of C. crambe, consistently occurred throughout all stages, an omnipresence that suggests vertical transmission from parents to offspring. This symbiont fluctuated in relative abundance across developmental stages, with pronounced prevalence in lecithotrophic stages. A major shift in microbial composition occurred as new settlers completed osculum formation and acquired filter-feeding capacity. Candidatus Beroebacter blanensis decreased significatively at this point. Microbial diversity peaked in filter-feeding stages, contrasting with the lower diversity of lecithotrophic stages. Furthermore, individual specific transmission patterns were detected, with greater microbial similarity between larvae and their respective parents compared to non-parental conspecifics. CONCLUSIONS: These findings suggest a putative vertical transmission of the dominant symbiont, which could provide some metabolic advantage to non-filtering developmental stages of C. crambe. The increase in microbiome diversity with the onset of filter-feeding stages likely reflects enhanced interaction with environmental microbes, facilitating horizontal transmission. Conversely, lower microbiome diversity in lecithotrophic stages, prior to filter feeding, suggests incomplete symbiont transfer or potential symbiont digestion. This research provides novel information on the dynamics of the microbiome through sponge ontogeny, on the strategies for symbiont acquisition at each ontogenetic stage, and on the potential importance of symbionts during larval development.

High compositional and functional similarity in the microbiome of deep-sea sponges.

Sponges largely depend on their symbiotic microbes for their nutrition, health, and survival. This is especially true in high microbial abundance (HMA) sponges, where filtration is usually deprecated in favor of a larger association with prokaryotic symbionts. Sponge-microbiome association is substantially less understood for deep-sea sponges than for shallow water species. This is most unfortunate, since HMA sponges can form massive sponge grounds in the deep sea, where they dominate the ecosystems, driving their biogeochemical cycles. Here, we assess the microbial transcriptional profile of three different deep-sea HMA sponges in four locations of the Cantabrian Sea and compared them to shallow water HMA and LMA (low microbial abundance) sponge species. Our results reveal that the sponge microbiome has converged in a fundamental metabolic role for deep-sea sponges, independent of taxonomic relationships or geographic location, which is shared in broad terms with shallow HMA species. We also observed a large number of redundant microbial members performing the same functions, likely providing stability to the sponge inner ecosystem. A comparison between the community composition of our deep-sea sponges and another 39 species of HMA sponges from deep-sea and shallow habitats, belonging to the same taxonomic orders, suggested strong homogeneity in microbial composition (i.e. weak species-specificity) in deep sea species, which contrasts with that observed in shallow water counterparts. This convergence in microbiome composition and functionality underscores the adaptation to an extremely restrictive environment with the aim of exploiting the available resources.

Development and Validation of a Prediction Model and Score for Transthyretin Cardiac Amyloidosis Diagnosis: T-Amylo.

BACKGROUND: Although transthyretin cardiac amyloidosis (ATTR-CA) is often underdiagnosed, clinical suspicion is essential for early diagnosis. OBJECTIVES: The aim of this study was to develop and validate a feasible prediction model and score to facilitate the diagnosis of ATTR-CA. METHODS: This retrospective multicenter study enrolled consecutive patients who underwent 99mTc-DPD scintigraphy for suspected ATTR-CA. ATTR-CA was diagnosed if Grade 2 or 3 cardiac uptake was evidenced on 99mTc-DPD scintigraphy in the absence of a detectable monoclonal component or by demonstration of amyloid by biopsy. A prediction model for ATTR-CA diagnosis was developed in a derivation sample of 227 patients from 2 centers using multivariable logistic regression with clinical, electrocardiography, analytical, and transthoracic echocardiography variables. A simplified score was also created. Both of them were validated in an external cohort (n = 895) from 11 centers. RESULTS: The obtained prediction model combined age, gender, carpal tunnel syndrome, interventricular septum in diastole thickness, and low QRS interval voltages, with an area under the curve (AUC) of 0.92. The score had an AUC of 0.86. Both the T-Amylo prediction model and the score showed a good performance in the validation sample (ie, AUC: 0.84 and 0.82, respectively). They were tested in 3 clinical scenarios of the validation cohort: 1) hypertensive cardiomyopathy (n = 327); 2) severe aortic stenosis (n = 105); and 3) heart failure with preserved ejection fraction (n = 604), all with good diagnostic accuracy. CONCLUSIONS: The T-Amylo is a simple prediction model that improves the prediction of ATTR-CA diagnosis in patients with suspected ATTR-CA.

Influence of the medical treatment schedule in new diagnoses patients with heart failure and reduced ejection fraction.

AIMS: Heart failure (HF) guidelines recommend treating all patients with HF and reduced ejection fraction (HFrEF) with quadruple therapy, although they do not establish how to start it. This study aimed to evaluate the implementation of these recommendations, analyzing the efficacy and safety of the different therapeutic schedules. METHODS AND RESULTS: Prospective, observational, and multicenter registry that evaluated the treatment initiated in patients with newly diagnosed HFrEF and its evolution at 3 months. Clinical and analytical data were collected, as well as adverse reactions and events during follow-up. Five hundred and thirty-three patients were included, selecting four hundred and ninety-seven, aged 65.5 ± 12.9 years (72% male). The most frequent etiologies were ischemic (25.5%) and idiopathic (21.1%), with a left ventricular ejection fraction of 28.7 ± 7.4%. Quadruple therapy was started in 314 (63.2%) patients, triple in 120 (24.1%), and double in 63 (12.7%). Follow-up was 112 days [IQI 91; 154], with 10 (2%) patients dying. At 3 months, 78.5% had quadruple therapy (p < 0.001). There were no differences in achieving maximum doses or reducing or withdrawing drugs (< 6%) depending on the starting scheme. Twenty-seven (5.7%) patients had any emergency room visits or admission for HF, less frequent in those with quadruple therapy (p = 0.02). CONCLUSION: It is possible to achieve quadruple therapy in patients with newly diagnosed HFrEF early. This strategy makes it possible to reduce admissions and visits to the emergency room for HF without associating a more significant reduction or withdrawal of drugs or significant difficulty in achieving the target doses.

Wild Fruits of Crataegus monogyna Jacq. and Sorbus aria (L.) Crantz: From Traditional Foods to Innovative Sources of Pigments and Antioxidant Ingredients for Food Products.

Hawthorn (Crataegus monogyna Jacq.) and whitebeam (Sorbus aria (L.) Crantz) are wild species traditionally used as ethnic foods in the Mediterranean area. Their red berries, and mainly the peels, may be used as ingredients due to their color (replacing other synthetic colorants) or functional properties. Some previous studies analyze all edible fruits, but there is very little literature on the composition and properties of the pulpless epidermis of the fruits of C. monogyna and no literature concerning the fruits of S. aria. Total phenolic compounds (TPC) and families of hydroxybenzoic acids, hydroxycinnamic acids, flavonols, and total monomeric anthocyanins were determined in the epidermis of C. monogyna and S. aria fruits. The in vitro antioxidant capacity was also determined using QUENCHER (Quick-Easy-New-CHEap-Reproducible) methodology. Anthocyanins profiles were analyzed in hydroalcoholic extracts through HPLC/MS. C. monogyna fruits presented higher content of TPC than S. aria, with hydroxybenzoic acids (2870.6 mg GAE/100g dw) as the major family, followed by flavonols (771.4 mg QE/100 g dw) and hydroxycinnamic acids (610.3 FAE/100 g dw). Anthocyanins were found in 251.7 mg cyanidin-3-glucoside/100 g dw, characterized by the content of cyanidin-O-hexoxide and peonidin-O-hexoxide. The levels of these compounds correlated with higher values of a* parameter (higher intensity of reddish color). These fruits also showed higher antioxidant capacity by Q-Folin-Ciocalteu and Q-FRAP. S. aria peels had fewer phenolic compounds, particularly anthocyanins (33.7 mg cyanidin-3-glucoside/100 g dw), containing different cyanidin derivatives. From these results, new insights about the composition of the epidermis of these wild fruits are provided, and their potential as ingredients for the food industry is corroborated.

Heart Transplantation in Systemic Sclerosis: A Therapeutic Option. Presentation of a Case and Literature Review.

Cardiac involvement in systemic sclerosis (SSc) is rare but leads to poor short-term prognosis. Evidence regarding heart transplantation (HT) is scarce and is based on experience with isolated cases. We present this case with the aim of analysing the characteristics of a patient with SS who has undergone a successful transplant.

Heart Transplantation in Systemic Sclerosis: A Therapeutic Option. Presentation of a Case and Literature Review / Trasplante cardíaco en esclerosis sistémica: una opción terapéutica. Presentación de un caso y revisión de la bibliografía

Cardiac involvement in systemic sclerosis (SSc) is rare but leads to poor short-term prognosis. Evidence regarding heart transplantation (HT) is scarce and is based on experience with isolated cases. We present this case with the aim of analysing the characteristics of a patient with SS who has undergone a successful transplant.(AU)

El compromiso cardíaco en la esclerosis sistémica (ES) es raro, pero conlleva un mal pronóstico a corto plazo. La evidencia relativa al trasplante cardíaco (TC) es escasa y se basa en la experiencia con los casos aislados. Presentamos este caso con el objetivo de analizar las características de un paciente con esclerosis sistémica sometido a un trasplante exitoso.(AU)

Communality in microbial stress response and differential metabolic interactions revealed by time-series analysis of sponge symbionts.

The diversity and function of sponge-associated symbionts is now increasingly understood; however, we lack an understanding of how they dynamically behave to ensure holobiont stability in the face of environmental variation. Here, we performed a metatransciptomic analysis on three microbial symbionts of the sponge Cymbastela concentrica in situ over 14 months and through differential gene expression and correlation analysis to environmental variables uncovered differences that speak to their metabolic activities and level of symbiotic and environmental interactions. The nitrite-oxidizing Ca. Porinitrospira cymbastela maintained a seemingly stable metabolism, with the few differentially expressed genes related only to stress responses. The heterotrophic Ca. Porivivens multivorans displayed differential use of holobiont-derived compounds and respiration modes, while the ammonium-oxidizing archaeon Ca. Nitrosopumilus cymbastelus differentially expressed genes related to phosphate metabolism and symbiosis effectors. One striking similarity between the symbionts was their similar variation in expression of stress-related genes. Our time-series study showed that the microbial community of C. concentrica undertakes dynamic gene expression adjustments in response to the surroundings, tuned to deal with general stress and metabolic interactions between holobiont members. The success of these dynamic adjustments likely underpins the stability of the sponge holobiont and may provide resilience against environmental change.

Stress response of the marine sponge Scopalina sp.. Can microbial community composition predict sponge disease?

Disease has become an increasingly recognised problem in the marine environment, but our understanding of the factors that drive disease or our ability to predict its occurrence is limited. Marine sponges are known for their close associations with microorganisms, which are generally accepted to underpin sponge health and function. The aim of this study is to explore whether the microbial community composition of sponges can act as a predictor of disease occurrence under stressful environmental conditions. The development of a naturally occurring disease in the temperate sponge species Scopalina sp. was reproducibly recreated in a flow-through aquarium environment using increasing temperature stress. Throughout the experiments, four morphological health states were observed and described. Fingerprinting based on terminal restriction fragment length polymorphism of the bacterial community uncovered a statistically significant signature in healthy sponges prior to stress or apparent symptoms that correlated with the time it took for the disease to occur. This shows that the bacterial community composition of individual sponges can act as predictors of necrotic disease development. To the best of our knowledge, this is the first time a microbial signature of this nature has been reported in marine sponges and this finding can contribute to unravelling cause-effect pathways for stress-related dysbiosis and disease.

Heart Transplantation in Systemic Sclerosis: A Therapeutic Option. Presentation of a Case and Literature Review.

Cardiac involvement in systemic sclerosis (SSc) is rare but leads to poor short-term prognosis. Evidence regarding heart transplantation (HT) is scarce and is based on experience with isolated cases. We present this case with the aim of analysing the characteristics of a patient with SS who has undergone a successful transplant.

On the way to specificity - Microbiome reflects sponge genetic cluster primarily in highly structured populations.

Most animals, including sponges (Porifera), have species-specific microbiomes. Which genetic or environmental factors play major roles structuring the microbial community at the intraspecific level in sponges is, however, largely unknown. In this study, we tested whether geographic location or genetic structure of conspecific sponges influences their microbial assembly. For that, we used three sponge species with different rates of gene flow, and collected samples along their entire distribution range (two from the Mediterranean and one from the Southern Ocean) yielding a total of 393 samples. These three sponge species have been previously analysed by microsatellites or single nucleotide polymorphisms, and here we investigate their microbiomes by amplicon sequencing of the microbial 16S rRNA gene. The sponge Petrosia ficiformis, with highly isolated populations (low gene flow), showed a stronger influence of the host genetic distance on the microbial composition than the spatial distance. Host-specificity was therefore detected at the genotypic level, with individuals belonging to the same host genetic cluster harbouring more similar microbiomes than distant ones. On the contrary, the microbiome of Ircinia fasciculata and Dendrilla antarctica - both with weak population structure (high gene flow) - seemed influenced by location rather than by host genetic distance. Our results suggest that in sponge species with high population structure, the host genetic cluster influence the microbial community more than the geographic location.

Evidence of Vent-Adaptation in Sponges Living at the Periphery of Hydrothermal Vent Environments: Ecological and Evolutionary Implications.

The peripheral areas of deep-sea hydrothermal vents are often inhabited by an assemblage of animals distinct to those living close to vent chimneys. For many such taxa, it is considered that peak abundances in the vent periphery relate to the availability of hard substrate as well as the increased concentrations of organic matter generated at vents, compared to background areas. However, the peripheries of vents are less well-studied than the assemblages of vent-endemic taxa, and the mechanisms through which peripheral fauna may benefit from vent environments are generally unknown. Understanding this is crucial for evaluating the sphere of influence of hydrothermal vents and managing the impacts of future human activity within these environments, as well as offering insights into the processes of metazoan adaptation to vents. In this study, we explored the evolutionary histories, microbiomes and nutritional sources of two distantly-related sponge types living at the periphery of active hydrothermal vents in two different geological settings (Cladorhiza from the E2 vent site on the East Scotia Ridge, Southern Ocean, and Spinularia from the Endeavour vent site on the Juan de Fuca Ridge, North-East Pacific) to examine their relationship to nearby venting. Our results uncovered a close sister relationship between the majority of our E2 Cladorhiza specimens and the species Cladorhiza methanophila, known to harbor and obtain nutrition from methanotrophic symbionts at cold seeps. Our microbiome analyses demonstrated that both E2 Cladorhiza and Endeavour Spinularia sp. are associated with putative chemosynthetic Gammaproteobacteria, including Thioglobaceae (present in both sponge types) and Methylomonaceae (present in Spinularia sp.). These bacteria are closely related to chemoautotrophic symbionts of bathymodiolin mussels. Both vent-peripheral sponges demonstrate carbon and nitrogen isotopic signatures consistent with contributions to nutrition from chemosynthesis. This study expands the number of known associations between metazoans and potentially chemosynthetic Gammaproteobacteria, indicating that they can be incredibly widespread and also occur away from the immediate vicinity of chemosynthetic environments in the vent-periphery, where these sponges may be adapted to benefit from dispersed vent fluids.

Tracing animal genomic evolution with the chromosomal-level assembly of the freshwater sponge Ephydatia muelleri.

The genomes of non-bilaterian metazoans are key to understanding the molecular basis of early animal evolution. However, a full comprehension of how animal-specific traits, such as nervous systems, arose is hindered by the scarcity and fragmented nature of genomes from key taxa, such as Porifera. Ephydatia muelleri is a freshwater sponge found across the northern hemisphere. Here, we present its 326 Mb genome, assembled to high contiguity (N50: 9.88 Mb) with 23 chromosomes on 24 scaffolds. Our analyses reveal a metazoan-typical genome architecture, with highly shared synteny across Metazoa, and suggest that adaptation to the extreme temperatures and conditions found in freshwater often involves gene duplication. The pancontinental distribution and ready laboratory culture of E. muelleri make this a highly practical model system which, with RNAseq, DNA methylation and bacterial amplicon data spanning its development and range, allows exploration of genomic changes both within sponges and in early animal evolution.

Ull vermell I exoftàlmia: a propòsit de dos casos d'inflamació orbitària idiopàtica / Ojo rojo y exoftalmos: a propósito de dos casos de inflamación orbitaria idiopática / Red eye and exophthalmos: report of two cases of idiopathic orbital inflammation

INTRODUCCIÓ: La inflamació orbitària idiopàtica (IOI), o pseudotumor orbitari idiopàtic, forma part del diagnòstic diferencial d'ull vermell I exoftàlmia. És una malaltia inflamatòria, benigna I sense causa identificable, que respon majoritàriament a corticoteràpia. L'interès de tots dos casos recau en la variabilitat de la resposta al tractament de primera línia I el maneig complex en casos d'evolució atípica. OBSERVACIÓ CLÍNICA: Cas 1. Nen de 12 anys amb ull vermell d'evolució tòrpida, associat posteriorment a exoftàlmia, quemosi I dolor ocular. Es va diagnosticar d'IOI, amb una resposta excel·lent a la corticoteràpia, però amb corticodependència a la retirada progressiva del fàrmac. Va necessitar biòpsia per l'evolució atípica I tractament immunosupressor. Cas 2. Nena de 6 anys amb cefalea frontal I rinorrea, orientada inicialment com a sinusitis. Posteriorment va presentar ull vermell, dolor ocular, exoftàlmia, diplopia I altres signes inflamatoris locals. Es va diagnosticar d'IOI I es va iniciar la corticoteràpia, amb resposta excel·lent I remissió. COMENTARIS: La IOI requereix un exhaustiu diagnòstic diferencial, amb un diagnòstic final d'exclusió que descarti l'associació de malalties sistèmiques. N'és característica la ràpida resposta a glucocorticoides. La corticodependència observada en el primer cas és poc freqüent, I va caldre un esglaó terapèutic superior per aconseguir el control dels símptomes

INTRODUCCIÓN: La inflamación orbitaria idiopática (IOI), o pseudotumor orbitario inflamatorio, forma parte del diagnóstico diferencial de ojo rojo y exoftalmos. Es una enfermedad inflamatoria, benigna y sin causa identificable, que responde mayoritariamente a corticoterapia. El interés de ambos casos recae en la variabilidad de la respuesta al tratamiento de primera línea y el manejo complejo en casos de evolución atípica. OBSERVACIÓN CLÍNICA: Caso 1. Niño de 12 años con ojo rojo de evolución tórpida, asociado posteriormente a exoftalmos, quemosis y dolor ocular. Se diagnosticó de IOI con excelente respuesta a corticoterapia, pero presentando corticodependencia a la retirada progresiva del fármaco. Precisó biopsia por la evolución atípica, y tratamiento inmunosupresor. Caso 2. Niña de 6 años con cefalea frontal y rinorrea, orientada inicialmente como sinusitis. Posteriormente presentó ojo rojo, dolor ocular, exoftalmos, diplopía y otros signos inflamatorios locales. Se diagnosticó de IOI y se inició corticoterapia, con excelente respuesta y remisión. COMENTARIOS: La IOI requiere un exhaustivo diagnóstico diferencial, con un diagnóstico final de exclusión descartando la asociación a enfermedades sistémicas. Es característica la rápida respuesta a glucocorticoides. La corticodependencia apreciada en el primer caso es poco frecuente, y se requirió un escalón terapéutico superior para conseguir el control de los síntomas

INTRODUCTION: Idiopathic orbital inflammation (IOI) or orbital inflammatory pseudotumor is within the differential diagnosis of red eye and exophthalmos, and it is defined as a benign inflammatory disease without identifiable cause that responds to corticosteroid therapy. The two cases reported here highlight the variability of the response to the first line treatment, and the complex management in cases of atypical evolution. Case 1: A 12-year-old boy presented with a red eye with indolent evolution associated with exophthalmos, chemosis and eye pain. He was diagnosed with IOI and had an excellent initial response to corticosteroid therapy. However, the disease was corticosteroiddependent requiring a biopsy for confirmation, and initiation of immunosuppressive therapy. Case 2: A 6-year-old girl presented with frontal headache and rhinorrhea and was initially diagnosed with sinusitis. She later presented with painful red eye, exophthalmos, diplopia and other local inflammatory signs. She was diagnosed with IOI and had an excellent response and long-term remission to corticosteroid therapy. COMMENTS: IOI requires a comprehensive differential diagnosis, with a final diagnosis of exclusion ruling out the association with systemic diseases. The rapid response to glucocorticoids is characteristic of IOI. Corticosteroid dependence is rare and requires an increment in immunosuppressive therapy for disease control

Vertical transmission of sponge microbiota is inconsistent and unfaithful.

Co-evolutionary theory predicts that if beneficial microbial symbionts improve host fitness, they should be faithfully transmitted to offspring. More recently, the hologenome theory of evolution predicts resemblance between parent and offspring microbiomes and high partner fidelity between host species and their vertically transmitted microbes. Here, we test these ideas in multiple coexisting host species with highly diverse microbiota, leveraging known parent-offspring pairs sampled from eight species of wild marine sponges (Porifera). We found that the processes governing vertical transmission were both neutral and selective. A neutral model was a better fit to larval (R2 = 0.66) than to the adult microbiota (R2 = 0.27), suggesting that the importance of non-neutral processes increases as the sponge host matures. Microbes that are enriched above neutral expectations in adults were disproportionately transferred to offspring. Patterns of vertical transmission were, however, incomplete: larval sponges shared, on average, 44.8% of microbes with their parents, which was not higher than the fraction they shared with nearby non-parental adults. Vertical transmission was also inconsistent across siblings, as larval sponges from the same parent shared only 17% of microbes. Finally, we found no evidence that vertically transmitted microbes are faithful to a single sponge host species. Surprisingly, larvae were as likely to share vertically transmitted microbes with larvae from other sponge species as they were with their own species. Our study demonstrates that common predictions of vertical transmission that stem from species-poor systems are not necessarily true when scaling up to diverse and complex microbiomes.

Delineation of ecologically distinct units of marine Bacteroidetes in the Northwestern Mediterranean Sea.

Bacteroidetes is one of the dominant phyla of ocean bacterioplankton, yet its diversity and population structure is poorly understood. To advance in the delineation of ecologically meaningful units within this group, we constructed near full-length 16S rRNA gene clone libraries from contrasting marine environments in the NW Mediterranean. Based on phylogeny and the associated ecological variables (depth and season), 24 different Bacteroidetes clades were delineated. By considering their relative abundance (from iTag amplicon sequencing studies), we described the distribution patterns of each of these clades, delimiting them as Ecologically Significant Taxonomic Units (ESTUs). Spatially, there was almost no overlap among ESTUs at different depths. In deep waters there was predominance of Owenweeksia, Leeuwenhoekiella, Muricauda-related genera, and some depth-associated ESTUs within the NS5 and NS2b marine clades. Seasonally, multi-annual dynamics of recurring ESTUs were present with dominance of some ESTUs within the NS4, NS5 and NS2b marine clades along most of the year, but with variable relative frequencies between months. A drastic change towards the predominance of Formosa-related ESTUs and one ESTU from the NS5 marine clade was typically present after the spring bloom. Even though there are no isolates available for these ESTUs to determine their physiology, correlation analyses identified the environmental preference of some of them. Overall, our results suggest that there is a high degree of niche specialisation within these closely related clades. This work constitutes a step forward in disentangling the ecology of marine Bacteroidetes, which are essential players in organic matter processing in the oceans.

The Evolutionary Consequences of Transposon-Related Pericentromer Expansion in Melon.

Transposable elements (TEs) are a major driver of plant genome evolution. A part from being a rich source of new genes and regulatory sequences, TEs can also affect plant genome evolution by modifying genome size and shaping chromosome structure. TEs tend to concentrate in heterochromatic pericentromeric regions and their proliferation may expand these regions. Here, we show that after the split of melon and cucumber, TEs have expanded the pericentromeric regions of melon chromosomes that, probably as a consequence, show a very low recombination frequency. In contrast, TEs have not proliferated to a high extent in cucumber, which has small TE-dense pericentromeric regions and shows a relatively constant recombination rate along chromosomes. These differences in chromosome structure also translate in differences in gene nucleotide diversity. Although gene nucleotide diversity is essentially constant along cucumber chromosomes, melon chromosomes show a bimodal pattern of genetic variability, with a gene-poor region where variability is negatively correlated with gene density. Interestingly, genes are not homogeneously distributed in melon, and the high variable low-recombining pericentromeric regions show a higher concentration of melon-specific genes whereas genes shared with cucumber and other plants are essentially found in gene-rich chromosomal arms. The results presented here suggest that melon pericentromeric regions may allow gene sequences to evolve more freely than in other chromosomal compartments which may allow new ORFs to arise and eventually be selected. These results show that TEs can drastically change the structure of chromosomes creating different chromosomal compartments imposing different constraints for gene evolution.