Modeling Dynamics of Human Gut Microbiota Derived from Gluten Metabolism: Obtention, Maintenance and Characterization of Complex Microbial Communities.

Western diets are rich in gluten-containing products, which are frequently poorly digested. The human large intestine harbors microorganisms able to metabolize undigested gluten fragments that have escaped digestion by human enzymatic activities. The aim of this work was obtaining and culturing complex human gut microbial communities derived from gluten metabolism to model the dynamics of healthy human large intestine microbiota associated with different gluten forms. For this purpose, stool samples from six healthy volunteers were inoculated in media containing predigested gluten or predigested gluten plus non-digested gluten. Passages were carried out every 24 h for 15 days in the same medium and community composition along time was studied via V3-V4 16S rDNA sequencing. Diverse microbial communities were successfully obtained. Moreover, communities were shown to be maintained in culture with stable composition for 14 days. Under non-digested gluten presence, communities were enriched in members of Bacillota, such as Lachnospiraceae, Clostridiaceae, Streptococcaceae, Peptoniphilaceae, Selenomonadaceae or Erysipelotrichaceae, and members of Actinomycetota, such as Bifidobacteriaceae and Eggerthellaceae. Contrarily, communities exposed to digested gluten were enriched in Pseudomonadota. Hence, this study shows a method for culture and stable maintenance of gut communities derived from gluten metabolism. This method enables the analysis of microbial metabolism of gluten in the gut from a community perspective.

Resistance of soil bacterial communities from montane heathland ecosystems in the Cantabrian mountains (NW Spain) to a gradient of experimental nitrogen deposition.

Elevated atmospheric nitrogen (N) deposition on terrestrial ecosystems has become one of the most important drivers of microbial diversity loss on a global scale, and has been reported to alter the soil function of nutrient-poor, montane Calluna vulgaris heathlands in the context of global change. In this work we analyze for the first time the shifts of bacterial communities in response to experimental addition of N in Calluna heathlands as a simulation of atmospheric deposition. Specifically, we evaluated the effects of five N addition treatments (0, 10, 20, and 50 kg N ha-1 yr-1 for 3-years; and 56 kg N ha-1 yr-1 for 10-years) on the resistance of soil bacterial communities as determined by changes in their composition and alpha and beta diversities. The study was conducted in montane Calluna heathlands at different development stages (young and mature phases) in the southern side of the Cantabrian Mountains (NW Spain). Our results evidenced a substantial increase of long-term (10-years) N inputs on soil extractable N-NH4+, particularly in young Calluna stands. The alpha diversity of soil bacterial communities in mature Calluna stands did not show a significant response to experimental N addition, whereas it was significantly higher under long-term chronic N addition (56 kg N ha-1 yr-1 for 10-years) in young Calluna stands. These bacterial community shifts are mainly attributable to a decrease in the dominance of Acidobacteria phylum, the most representative in montane Calluna ecosystems, in favor of copiotrophic taxa such as Actinobacteria or Proteobacteria phyla, favored under increased N availability. Future research should investigate what specific ecosystem functions performed by soil bacterial communities may be sensitive to increased nitrogen depositions, which may have substantial implications for the understanding of montane Calluna ecosystems' stability.

High resilience of soil bacterial communities to large wildfires with an important stochastic component.

Wildfires alter the structure and functioning of ecosystems through changes in their biotic and abiotic components. A deeper understanding recovery process concerning diverse communities and properties within these components can provide valuable insights into the ecological effects of wildfires. Therefore, it is appropriate to enhance our understanding of the resilience of bacterial communities after wildfires within Mediterranean ecosystems. In this research, soil bacterial community resilience was evaluated in three types of ecosystems for two fire severities, two years after a large wildfire in Mediterranean ecosystems. The resilience of the soil bacterial community refers to its ability to return to original state after disturbance. This capacity can be estimated by the study of its recovery over time. In this study we evaluated the resilience using the variables: alpha diversity, beta diversity and the changes in abundance of both OTUs (Operational Taxonomic Units) and principal bacterial taxa (phyla, classes or orders). Our results showed that resilience depends on fire severity and type of ecosystem. We studied three ecosystems with different stage in the secondary succession: low maturity shrublands and heathlands, and high maturity oak forests. In general, high resilience in the soil bacterial community was observed in heathlands under low and high fire severity conditions. The other two ecosystems were resilient only under low fire severity. Stochastic replacement of the abundance of the OTUs was observed in all three ecosystems, with a notable impact on oak forests, under during high-severity conditions.

Short-term responses of ecosystem multifunctionality to fire severity are modulated by fire-induced impacts on plant and soil microbial communities.

This study represents a first attempt to shed light into the mechanisms that modulate the response of ecosystem multifunctionality (EMF) to fire severity in post-fire landscapes. We specifically investigated the role played by fire-induced changes on above and belowground communities in the modulation of EMF responses at short-term after fire. For this purpose, we estimated EMF using an averaging approach from three ecosystem functions (carbon regulation, decomposition and soil fertility) and their standardized functional indicators in field plots burned at low and high fire severity 1-year after a wildfire occurred in a Mediterranean ecosystem in the central region of Spain. Plant taxonomic and functional richness, and the bacterial and fungal taxonomic richness, were measured in the plots as community properties with a potential intermediate control over fire severity effects on EMF. The ecological effects of fire severity on above and belowground communities were important in shaping EMF as evidenced by Structural Equation Modeling (SEM). Indeed, the evidenced shrinkage exerted by high fire severity on EMF at short-term after fire was not direct, but modulated by fire-induced effects on the plant functional richness and the microbial taxonomic richness. However, EMF variation was more strongly modulated by indirect effects of fire severity on the biodiversity of soil microbial communities, than by the effects on the plant communities. Particularly, the fungal community exerted the strongest intermediate control (standardized SEM ß coefficient = 0.62), which can be linked to the differential response of bacterial (ß = -0.36) and fungal (ß = -0.84) communities to fire severity evidenced here. Our findings demonstrate that the effects of fire severity on above and belowground communities are important drivers of short-term ecosystem functioning. Efforts tailored to secure the provision of multiple functions should be focused on promoting the recovery on soil microbial communities under high-severity scenarios.

The effect of sheep grazing abandonment on soil bacterial communities in productive mountain grasslands.

Livestock grazing abandonment entails important shifts on the overall ecosystem function, but the effects of this land-use change on specific bacterial taxa remain poorly understood in mountain grasslands. Moreover, we currently lack knowledge about the feedbacks between changes in ecosystem functions affected by livestock abandonment in mountain grasslands and the soil bacterial communities. Here, we evaluated the behavior of bacterial communities' structure and composition at taxa level as a function of short (1-year) and long-term (15-years) grazing abandonment in a mountain grassland. We also linked the observed responses in the bacterial communities to changes in several ecosystem functions (i.e. primary production, plant species biodiversity, carbon stocks and soil fertility). The alpha diversity of the bacterial communities did not show a significant response as a consequence of grazing abandonment. However, we identified significant changes on the overall composition of soil bacterial communities between the long-term abandoned grassland areas and grazed or abandoned areas in the short term. We also evidenced a balance between the number of operational taxonomic units (OTUs) whose relative abundance is favored by livestock grazing (19.51 %) and those with higher relative abundances in long-term grazing exclusion areas (20.23 %) that could behave as indicators of grazing abandonment. Structural Equation Modeling analyses proved that several bacterial taxa associated with relevant ecosystem functions, such as Rhodospirillales order within Alphaproteobacteria phylum, featured significant changes in their relative abundance between grazing treatments. The direct and indirect effects of grazing exclusion on woody species encroachment and soil organic carbon were strongly linked to the changes in the abundance of bacterial taxa indicators. The assessment of the bacterial community response to livestock abandonment in mountain grasslands may thus provide early warning signs before subtle changes in ecosystem functions occur.

Distribution, Function, and Evolution of a Gene Essential for Trichothecene Toxin Biosynthesis in Trichoderma.

Trichothecenes are terpenoid toxins produced by species in 10 fungal genera, including species of Trichoderma. The trichothecene biosynthetic gene (tri) cluster typically includes the tri5 gene, which encodes a terpene synthase that catalyzes formation of trichodiene, the parent compound of all trichothecenes. The two Trichoderma species, Trichoderma arundinaceum and T. brevicompactum, that have been examined are unique in that tri5 is located outside the tri cluster in a genomic region that does not include other known tri genes. In the current study, analysis of 35 species representing a wide range of the phylogenetic diversity of Trichoderma revealed that 22 species had tri5, but only 13 species had both tri5 and the tri cluster. tri5 was not located in the cluster in any species. Using complementation analysis of a T. arundinaceum tri5 deletion mutant, we demonstrated that some tri5 homologs from species that lack a tri cluster are functional, but others are not. Phylogenetic analyses suggest that Trichoderma tri5 was under positive selection following its divergence from homologs in other fungi but before Trichoderma species began diverging from one another. We propose two models to explain these diverse observations. One model proposes that the location of tri5 outside the tri cluster resulted from loss of tri5 from the cluster in an ancestral species followed by reacquisition via horizontal transfer. The other model proposes that in species that have a functional tri5 but lack the tri cluster, trichodiene production provides a competitive advantage.

Wildfire effects on diversity and composition in soil bacterial communities.

In recent years, the Mediterranean area has witnessed an increase of both the frequency and severity of large fires, which appears to be intimately associated with climate and land use changes. To measure the impact of wildfires on living organisms, diverse indicators have been proposed. These indicators of fire severity traditionally rely on quantifying the damage caused to the vegetal component of ecosystems. However, the use of bacterial communities as severity indicators has received less attention. Here, we studied the differences between bacterial communities of three different Mediterranean ecosystems, two shrubby and one arboreal, two months after a large wildfire. Two levels of severity were compared to a control unburnt soil. The results showed that greater fire severity triggers a reduction in the diversity of soil bacterial communities. In high-severity fires, this reduction reached 40.6 and 58.6% of the control values for richness and Shannon's diversity, respectively. We also found that the greatest differences between communities could be attributed first to the severity of the fire, and second to the ecosystem from which they originated. Importantly, species of just five families of bacteria: Oxalobacteraceae, Micrococcaceae, Paenibacillaceae, Bacillaceae and Planococcaceae, became dominant in all three ecosystems. The average frequency increase for particular species was 100 times. However, due to random uncontrolled factors, the species that became dominant in each community were not always the same.

An altered fecal microbiota profile in patients with non-alcoholic fatty liver disease (NAFLD) associated with obesity.

INTRODUCTION: increasing evidence suggests a role of intestinal dysbiosis in obesity and non-alcoholic fatty liver disease (NAFLD). The advances in recent years with regard to the role of the gut microbiota raise the potential utility of new therapeutic approaches based on the modification of the microbiome. OBJECTIVE: the aim of this study was to compare the bacterial communities in obese patients with or without NAFLD to those of healthy controls. PATIENTS AND METHODS: the fecal microbiota composition of 20 healthy adults, 36 obese patients with NAFLD and 17 obese patients without NAFLD was determined by 16S ribosomal RNA sequencing using the Illumina MiSeq system. RESULTS: the results highlighted significant differences in the phylum Firmicutes between patients with and without NAFLD, which was a determining factor of the disease and supported its possible role as a marker of NAFLD. At the genus level, the relative abundance of Blautia, Alkaliphilus, Flavobacterium and Akkermansia was reduced in obese patients, both with or without NAFLD, compared to healthy controls. Furthermore, the number of sequences from the genus Streptococcus was significantly higher in patients with NAFLD in comparison with individuals without the disease, constituting another possible marker. Comparison of bacterial communities at the genus level by a principal coordinate analysis indicated that the bacterial communities of patients with NAFLD were dispersed and did not form a group. CONCLUSION: in conclusion, these results indicate the role of intestinal dysbiosis in the development of NAFLD associated with obesity. There was a differential microbiota profile between obese patients, with and without NAFLD. Thus, supporting gut microbiota modulation as a therapeutic alternative for the prevention and treatment of NAFLD.

Developing tools for evaluating inoculation methods of biocontrol Streptomyces sp. strains into grapevine plants.

The endophytic Streptomyces sp. VV/E1, and rhizosphere Streptomyces sp. VV/R4 strains, isolated from grapevine plants were shown in a previous work to reduce the infection rate of fungal pathogens involved in young grapevine decline. In this study we cloned fragments from randomly amplified polymorphic DNA (RAPD), and developed two stably diagnostic sequence-characterized amplified region (SCAR) markers of 182 and 160 bp for the VV/E1 and VV/R4 strains, respectively. The SCAR markers were not found in another 50 actinobacterial strains isolated from grapevine plants. Quantitative real-time PCR protocols based on the amplification of these SCAR markers were used for the detection and quantification of both strains in plant material. These strains were applied on young potted plants using two methods: perforation of the rootstock followed by injection of the microorganisms or soaking the root system in a bacterial suspension. Both methods were combined with a booster treatment by direct addition of a bacterial suspension to the soil near the root system. Analysis of uprooted plants showed that those inoculated by injection exhibited the highest rate of colonization. In contrast, direct addition of either strain to the soil did not lead to reliable colonization. This study has developed molecular tools for analyzing different methods for inoculating grapevine plants with selected Streptomyces sp. strains which protect them from fungal infections that enter through their root system. These tools are of great applied interest since they could easily be established in nurseries to produce grafted grapevine plants that are protected against fungal pathogens. Finally, this methodology might also be applied to other vascular plants for their colonization with beneficial biological control agents.

A genome-wide identification and comparative analysis of the lentil MLO genes.

Powdery mildew is a widespread fungal plant disease that can cause significant losses in many crops. Some MLO genes (Mildew resistance locus O) have proved to confer a durable resistance to powdery mildew in several species. Resistance granted by the MLO gene family members has prompted an increasing interest in characterizing these genes and implementing their use in plant breeding. Lentil (Lens culinaris Medik.) is a widely grown food legume almost exclusively consumed as dry seed with an average world production of 4.5 million tons. Powdery mildew causes severe losses on certain lentil cultivars under particular environmental conditions. Data mining of the lentil CDC Redberry draft genome allowed to identify up to 15 gene sequences with homology to known MLO genes, designated as LcMLOs. Further characterization of these gene sequences and their deduced protein sequences demonstrated conformity with key MLO protein characteristics such as the presence of transmembrane and calmodulin binding domains, as well as that of other conserved motifs. Phylogenetic and other comparative analyses revealed that LcMLO1 and LcMLO3 are the most likely gene orthologs related to powdery mildew response in other species, sharing a high similarity with other known resistance genes of dicot species, such as pea PsMLO1 and Medicago truncatula MtMLO1 and MtMLO3. Sets of primers were designed as tools to PCR amplify the genomic sequences of LcMLO1 and LcMLO3, also to screen lentil germplasm in search of resistance mutants. Primers were used to obtain the complete sequences of these two genes in all of the six wild lentil relatives. Respective to each gene, all Lens sequences shared a high similarity. Likewise, we used these primers to screen a working collection of 58 cultivated and 23 wild lentil accessions in search of length polymorphisms present in these two genes. All these data widen the insights on this gene family and can be useful for breeding programs in lentil and close related species.

Obtaining retrotransposon sequences, analysis of their genomic distribution and use of retrotransposon-derived genetic markers in lentil (Lens culinaris Medik.).

Retrotransposons with long terminal repeats (LTR-RTs) are widespread mobile elements in eukaryotic genomes. We obtained a total of 81 partial LTR-RT sequences from lentil corresponding to internal retrotransposon components and LTRs. Sequences were obtained by PCR from genomic DNA. Approximately 37% of the LTR-RT internal sequences presented premature stop codons, pointing out that these elements must be non-autonomous. LTR sequences were obtained using the iPBS technique which amplifies sequences between LTR-RTs. A total of 193 retrotransposon-derived genetic markers, mainly iPBS, were used to obtain a genetic linkage map from 94 F7 inbred recombinant lines derived from the cross between the cultivar Lupa and the wild ancestor L. culinaris subsp. orientalis. The genetic map included 136 markers located in eight linkage groups. Clusters of tightly linked retrotransposon-derived markers were detected in linkage groups LG1, LG2, and LG6, hence denoting a non-random genomic distribution. Phylogenetic analyses identified the LTR-RT families in which internal and LTR sequences are included. Ty3-gypsy elements were more frequent than Ty1-copia, mainly due to the high Ogre element frequency in lentil, as also occurs in other species of the tribe Vicieae. LTR and internal sequences were used to analyze in silico their distribution among the contigs of the lentil draft genome. Up to 8.8% of the lentil contigs evidenced the presence of at least one LTR-RT similar sequence. A statistical analysis suggested a non-random distribution of these elements within of the lentil genome. In most cases (between 97% and 72%, depending on the LTR-RT type) none of the internal sequences flanked by the LTR sequence pair was detected, suggesting that defective and non-autonomous LTR-RTs are very frequent in lentil. Results support that LTR-RTs are abundant and widespread throughout of the lentil genome and that they are a suitable source of genetic markers useful to carry out further genetic analyses.

Basic Oxygen Furnace steel slag aggregates for phosphorus treatment. Evaluation of its potential use as a substrate in constructed wetlands.

Basic Oxygen Furnace (BOF) steel slag aggregates from NW Spain were tested in batch and column experiments to evaluate its potential use as a substrate in constructed wetlands (CWs). The objectives of this study were to identify the main P removal mechanisms of BOF steel slag and determine its P removal capacity. Also, the results were used to discuss the suitability of this material as a substrate to be used in CWs. Batch experiments with BOF slag aggregates and increasing initial phosphate concentrations showed phosphate removal efficiencies between 84 and 99% and phosphate removal capacities from 0.12 to 8.78 mg P/g slag. A continuous flow column experiment filled with BOF slag aggregates receiving an influent synthetic solution of 15 mg P/L during 213 days showed a removal efficiency greater than 99% and a phosphate removal capacity of 3.1 mg P/g slag. In both experiments the main P removal mechanism was found to be calcium phosphate precipitation which depends on Ca(2+) and OH(-) release from the BOF steel slag after dissolution of Ca(OH)2 in water. P saturation of slag was reached within the upper sections of the column which showed phosphate removal capacities between 1.7 and 2.5 mg P/g slag. Once Ca(OH)2 was completely dissolved in these column sections, removal efficiencies declined gradually from 99% until reaching stable outlet concentrations with P removal efficiencies around 7% which depended on influent Ca(2+) for limited continuous calcium phosphate precipitation.

Influence of environmental variables on the structure and composition of soil bacterial communities in natural and constructed wetlands.

Bacteria are key players in wetland ecosystems, however many essential aspects regarding the ecology of wetland bacterial communities remain unknown. The present study characterizes soil bacterial communities from natural and constructed wetlands through the pyrosequencing of 16S rDNA genes in order to evaluate the influence of wetland variables on bacterial community composition and structure. The results show that the composition of soil bacterial communities was significantly associated with the wetland type (natural or constructed wetland), the type of environment (lagoon, Typha or Salix) and three continuous parameters (SOM, COD and TKN). However, no clear associations were observed with soil pH. Bacterial diversity values were significantly lower in the constructed wetland with the highest inlet nutrient concentrations. The abundances of particular metabolic groups were also related to wetland characteristics.

New insights into Capsicum spp relatedness and the diversification process of Capsicum annuum in Spain.

The successful exploitation of germplasm banks, harbouring plant genetic resources indispensable for plant breeding, will depend on our ability to characterize their genetic diversity. The Vegetable Germplasm Bank of Zaragoza (BGHZ) (Spain) holds an important Capsicum annuum collection, where most of the Spanish pepper variability is represented, as well as several accessions of other domesticated and non-domesticated Capsicum spp from all over the five continents. In the present work, a total of 51 C. annuum landraces (mainly from Spain) and 51 accessions from nine Capsicum species maintained at the BGHZ were evaluated using 39 microsatellite (SSR) markers spanning the whole genome. The 39 polymorphic markers allowed the detection of 381 alleles, with an average of 9.8 alleles per locus. A sizeable proportion of alleles (41.2%) were recorded as specific alleles and the majority of these were present at very low frequencies (rare alleles). Multivariate and model-based analyses partitioned the collection in seven clusters comprising the ten different Capsicum spp analysed: C. annuum, C. chinense, C. frutescens, C. pubescens, C. bacatum, C. chacoense and C. eximium. The data clearly showed the close relationships between C. chinense and C. frutescens. C. cardenasii and C. eximium were indistinguishable as a single, morphologically variable species. Moreover, C. chacoense was placed between C. baccatum and C. pubescens complexes. The C. annuum group was structured into three main clusters, mostly according to the pepper fruit shape, size and potential pungency. Results suggest that the diversification of C. annuum in Spain may occur from a rather limited gene pool, still represented by few landraces with ancestral traits. This ancient population would suffer from local selection at the distinct geographical regions of Spain, giving way to pungent and elongated fruited peppers in the South and Center, while sweet blocky and triangular types in Northern Spain.

Characterisation of the soil bacterial community structure and composition of natural and constructed wetlands.

In the present study, the pyrosequencing of 16S ribosomal DNA was used to characterise the soil bacterial community composition of a constructed wetland receiving municipal wastewater and a nearby natural wetland. Soil samples were taken from different locations in each wetland (lagoon, zone with T. latifolia, zone with S. atrocinerea). Moreover, the water quality parameters were evaluated (pH, Tª, conductivity, dissolved oxygen, redox potential, nutrients and suspended solids), revealing that the organic matter and nutrient contents were significantly higher in the constructed wetland than in the natural one. In general, the bacterial communities of the natural wetland were more diverse than those of the constructed wetland. The major phylogenic groups of all soils included Proteobacteria, Verrucomicrobia and Chloroflexi, with Proteobacteria being the majority of the community composition. The Verrucomicrobia and Chloroflexi phyla were more abundant in the natural wetland than the constructed wetland; in contrast, the Proteobacteria phylum was more abundant in the constructed wetland than the natural wetland. Beta diversity analyses reveal that the soil bacterial communities in the natural wetland were less dissimilar to each other than to those of the constructed wetland.

Differences in faecal bacteria populations and faecal bacteria metabolism in healthy adults and celiac disease patients.

UNLABELLED: Differences in the intestinal microbiota between children and adults with celiac disease (CD) have been reported; however, differences between healthy adults and adults with CD have not been clearly demonstrated. The aim of this study was to evaluate the differences in the intestinal microbiota between adults with CD and healthy individuals. Microbial communities in faecal samples were evaluated by PCR-denaturing gradient gel electrophoresis (DGGE) and gas-liquid chromatography of short chain fatty acids (SCFAs). The study group included 10 untreated CD patients, 11 treated CD patients and 11 healthy adults (in normal gluten diet and in GFD). UPGMA clustered the dominant microbial communities of healthy individuals together and separated them from the dominant microbial communities of the untreated CD patients. Most of the dominant microbial communities of the treated CD patients clustered together with those of healthy adults. The treated CD patients showed a reduction in the diversity of Lactobacillus and Bifidobacterium species. The presence of Bifidobacterium bifidum was significantly higher in untreated CD patients than healthy adults. There was a significant difference between untreated CD patients and healthy adults, as well as between treated CD patients and healthy adults, regarding acetic acid, propionic acid, butyric acid, and total SCFAs. IN CONCLUSION: healthy adults have a different faecal microbiota from that of untreated CD patients. A portion of the treated CD patients displayed a restored "normal" microbiota. The treated CD patients significantly reduce the Lactobacillus and Bifidobacterium diversity. Healthy adults have a different faecal SCFAs content from that of CD patients.

Comparative analysis of the composition of bacterial communities from two constructed wetlands for municipal and swine wastewater treatment.

This work provides information about bacterial community structure in natural wastewater treatment systems treating different types of wastewater. The diversity and composition of bacterial communities associated with the rhizosphere of Typha latifolia and Salix atrocinerea were studied and compared among two different natural wastewater treatment systems, using the direct sequencing of the 16S ribosomal RNA codifying genes. Phylogenetic affiliations of the bacteria detected allowed us to define the main groups present in these particular ecosystems. Moreover, bacterial community structure was studied through two diversity indices. Ten identified and five non-identified phyla were found in the samples; the phylum Proteobacteria was the predominant group in the four ecosystems. The results showed a bacterial community dominated by beta-proteobacteria and a lower diversity value in the swine wastewater treatment system. The municipal wastewater treatment system presented a high diverse community in both macrophytes (Typha latifolia and Salix atrocinerea), with gamma-proteobacteria and alpha-proteobacteria, respectively, as the most abundant groups.

Molecular evolutionary analyses of the Arabidopsis L7 ribosomal protein gene family.

Cytoplasmic ribosomal protein (r-protein) genes in Arabidopsis thaliana are encoded by 80 multigene families that contain between two and seven members. Gene family members are typically similar at the protein sequence level, with the most divergent members of any gene family retaining 94% identity, on average. However, three Arabidopsis r-protein families - S15a, L7 and P2 - contain highly divergent family members. Here, we investigated the organization, structure, expression and molecular evolution of the L7 r-protein family. Phylogenetic analyses showed that L7 r-protein gene family members constitute two distinct phylogenetic groups. The first group including RPL7B, RPL7C and RPL7D has homologs in plants, animals and fungi. The second group represented by RPL7A is found in plants but has no orthologs from other fully-sequenced eukaryotic genomes. These two groups may have derived from a duplication event prior to the divergence of animals and plants. All four L7 r-protein genes are expressed and all exhibit a differential expression in inflorescence and flowers. RPL7A and RPL7B are less expressed than the other genes in all tissues analyzed. Molecular characterization of nucleic and protein sequences of L7 r-protein genes and analysis of their codon usage did not indicate any functional divergence. The probable evolution of an extra-ribosomal function of group 2 genes is discussed.