Association of a CONSTANS-LIKE gene to flowering and height in autotetraploid alfalfa

In alfalfa (Medicago sativa), an autotetraploid forage legume, stem length is a major component of forage yield, quality and competing ability. In this species, flowering date is not a breeding criterion. Association mapping based on a candidate gene approach has given good results in plants, including autotetraploid species for which genetic analyses are complex. The role of a CONSTANS-LIKE gene, identified as a candidate for stem elongation and flowering date in the model legume M. truncatula, was tested for association with the same traits in alfalfa. Four hundred genotypes from ten cultivars were evaluated for stem height and flowering date in two locations during 4 years. They were genotyped with simple sequence repeat markers and a low structuration was noticed. Primers were designed to amplify and sequence two regions of the alfalfa gene homologous to CONSTANS-LIKE. Single nucleotide polymorphisms (SNPs) were detected and their allelic dose in each genotype was scored. Linkage disequilibrium within CONSTANS-LIKE rapidly decreased as expected. Eight SNPs with a frequency above 10% were detected over 1,010 bp (one SNP every 126 bp on average) in the 400 genotypes. This number was lower than observed in a neutral gene (a SNP every 31 bp on average). Highly significant associations of three SNPs to flowering date and stem height were identified. Each SNP explained up to 4.2% of the genetic variance. Thus, as in the model species, the CONSTANS-LIKE gene was shown to be involved in flowering date and stem height in alfalfa

Dental Arch Relations Analysed in a 14th Century Fossil Skull of the Sao Tribe, Cameroon

Dental occlusal relations are rarely reported in paleo-anthropology. The manipulation of hemi-arch replicas, as well as the superimposition of drawings on calques traced from photographs, facilitated the description of the intraand interarch relations. The occlusal interarch confrontation and the intermolar relation were observed and assessed in the horizontal, frontal and sagittal planes. Some measurements were helpful in the functional study. On the basis of knowledge in mandible kinematics a movement envelope of the first molar displacement during mastication was proposed. The dentition studied here was highly regular. It was a fine example of balanced wear for post-canine sectors. In spite of the lower canine extrusion, due to tribal mutilation of anterior teeth and to subsequent labret wearing, the interarch relations seemed not to have been altered

Dental Contribution to Paleo-Odontological Study of Interarch Relations in a Human Fossil

In paleo-anthropology the fragility of fossil pieces (teeth and supporting bones) reduces their possible manipulation when studying the interarch relations. Two original impression methods of the jaw pieces are proposed, both adapted from those currently practiced in odontology. The plaster replicas of the dental occlusal parts are prepared according to the manufacturing procedures used in prosthetic dental laboratories. This study led to the following observations: 1) the impression techniques used by odontologists are adapted to the moulding of fragile samples. 2) The replicas elaborated from these mouldings made easier the cast manipulation in confrontation. 3) Macrophotography is a complement to direct observation of the pieces and their replicas. 4) For paleoanthropologic purposes, such studies can be easily carried out on almost any animal or human fossils

A clarified position for solanum lycopersicum var. cerasiforme in the evolutionary history of tomatoes (solanaceae)

The natural phenotypic variability present in the germplasm of cultivated plants can be linked to molecular polymorphisms using association genetics. However it is necessary to consider the genetic structure of the germplasm used to avoid false association. The knowledge of genetic structure of plant populations can help in inferring plant evolutionary history. In this context, we genotyped 360 wild, feral and cultivated accessions with 20 simple sequence repeat markers and investigated the extent and structure of the genetic variation. The study focused on the red fruited tomato clade involved in the domestication of tomato and confirmed the admixture status of cherry tomatoes (Solanum lycopersicum var. cerasiforme). We used a nested sample strategy to set-up core collection maximizing the genetic diversity with a minimum of individuals. Results Molecular diversity was considerably lower in S. lycopersicum i.e. the domesticated form. Model-based analysis showed that the 144 S. lycopersicum var. cerasiforme accessions were structured into two groups: one close to the domesticated group and one resulting from the admixture of the S. lycopersicum and S. pimpinellifolium genomes. SSR genotyping also indicates that domesticated and wild tomatoes have evolved as a species complex with intensive level of hybridization. We compiled genotypic and phenotypic data to identify sub-samples of 8, 24, 32 and 64 cherry tomato accessions that captured most of the genetic and morphological diversity present in the entire S. lycopersicum var. cerasiforme collection. Conclusion The extent and structure of allelic variation is discussed in relation to historical events like domestication and modern selection. The potential use of the admixed group of S. lycopersicum var. cerasiforme for association genetics studies is also discussed. Nested core collections sampled to represent tomato diversity will be useful in diversity studies. Molecular and phenotypic variability of these core collections is defined. These collections are available for the scientific community and can be used as standardized panels for coordinating efforts on identifying novel interesting genes and on examining the domestication process in more detail

Do we need to consider grape phyllosphere microbiome in breeding schemes?

The aerial surface of the plant (phyllosphere) is the habitat of complex microbial communities. These communities may have profound effects on host plant health and its performance traits. When breeding new cultivars, i.e. the aerial component of a grape plant, one can simply ignore the phyllosphere in breeding schemes if its composition is mainly dependent on the environment. It is considered an important component if the genotype is the main driver of the phyllosphere composition. In order to answer this question, we have analysed several factors influencing the structure of the phyllosphere microbial community. Using amplicon sequencing of the 16S rRNA gene and of the internal transcribed spacer (ITS), we explored the microbial diversity at genus level for both bacteria and fungi present in the phyllosphere of leaves and grape berries. We analysed it on different grape taxonomic level (between five Vitis species or a set of Vitis vinifera cultivars chosen to represent the three genetic pools of the species), for different years and on five commercially important varieties of Vitis vinifera that were sampled from three different French terroirs. Our results indicated the presence of complex microbial diversity and assemblages in the phyllosphere. A significant effect of several factors (organ, grape species, growing year and terroir) on taxa abundance was observed with varying degrees of effect. At a given location, genotypes have an impact on microbial assemblage in the phyllosphere of leaf and berries, most pronounced on fruits but the effect of terroir was much stronger than the cultivar identity when the leaf phyllosphere of five grapevine varieties grown in different agro-climatic zones was compared. Limitations of the study as well as implied consequences of this work will be discussed

Adaptive evolution of the symbiotic gene NORK is not correlated with shifts of rhizobial specificity in the genus Medicago

<p>Abstract</p> <p>Background</p> <p>The <it>NODULATION RECEPTOR KINASE </it>(<it>NORK</it>) gene encodes a Leucine-Rich Repeat (LRR)-containing receptor-like protein and controls the infection by symbiotic rhizobia and endomycorrhizal fungi in Legumes. The occurrence of numerous amino acid changes driven by directional selection has been reported in this gene, using a limited number of messenger RNA sequences, but the functional reason of these changes remains obscure. The <it>Medicago </it>genus, where changes in rhizobial associations have been previously examined, is a good model to test whether the evolution of <it>NORK </it>is influenced by rhizobial interactions.</p> <p>Results</p> <p>We sequenced a region of 3610 nucleotides (encoding a 392 amino acid-long region of the NORK protein) in 32 <it>Medicago </it>species. We confirm that positive selection in <it>NORK </it>has occurred within the <it>Medicago </it>genus and find that the amino acid positions targeted by selection occur in sites outside of solvent-exposed regions in LRRs, and other sites in the N-terminal region of the protein. We tested if branches of the <it>Medicago </it>phylogeny where changes of rhizobial symbionts occurred displayed accelerated rates of amino acid substitutions. Only one branch out of five tested, leading to <it>M. noeana</it>, displays such a pattern. Among other branches, the most likely for having undergone positive selection is not associated with documented shift of rhizobial specificity.</p> <p>Conclusion</p> <p>Adaptive changes in the sequence of the NORK receptor have involved the LRRs, but targeted different sites than in most previous studies of LRR proteins evolution. The fact that positive selection in <it>NORK </it>tends not to be associated to changes in rhizobial specificity indicates that this gene was probably not involved in evolving rhizobial preferences. Other explanations (<it>e.g</it>. coevolutionary arms race) must be tested to explain the adaptive evolution of <it>NORK</it>.</p