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Abstract The chloroplast genome originated from photosynthetic organisms and has retained the core genes that mainly encode components of photosynthesis. However, the causes of variations in chloroplast genome size in seed plants have only been thoroughly analyzed within small subsets of spermatophytes. In this study, we conducted the first comparative analysis on a large scale to examine the relationship between sequence characteristics and genome size in 272 seed plants based on cross-species and phylogenetic signal analysis. Our results showed that inverted repeat regions, large or small single copies, intergenic regions, and gene number can be attributed to the variations in chloroplast genome size among closely related species. However, chloroplast gene length underwent evolution affecting chloroplast genome size in seed plants irrespective of whether phylogenetic information was incorporated. Among chloroplast genes, atpA, accD and ycf1 account for 13% of the variation in genome size, and the average Ka/Ks values of homologous pairs of the three genes are larger than 1. The relationship between chloroplast genome size and gene length might be affected by selection during the evolution of spermatophytes. The variation in chloroplast genome size may influence energy generation and ecological strategy in seed plants.

Introduction Seed size has long been recognized as an important contributor to habitat-specific adaptation in plants (Chapin et al. 1993). Production of larger seeds can provide fitness advantages in unfavorable [...], Seed size is variable within many plant species, and understanding the underlying genetic factors can provide insights into mechanisms of local environmental adaptation. Here we make use of the abundant genomic and germplasm resources available for rice (Oryza sativa) to perform a large-scale genome-wide association study (GWAS) of grain width. Grain width varies widely within the crop and is also known to show climate-associated variation across populations of its wild progenitor. Using a filtered dataset of >1.9 million genome-wide SNPs in a sample of 570 cultivated and wild rice accessions, we performed GWAS with two complementary models, GLM and MLM. The models yielded 10 and 33 significant associations, respectively, and jointly yielded seven candidate locus regions, two of which have been previously identified. Analyses of nucleotide diversity and haplotype distributions at these loci revealed signatures of selection and patterns consistent with adaptive introgression of grain width alleles across rice variety groups. The results provide a 50% increase in the total number of rice grain width loci mapped to date and support a polygenic model whereby grain width is shaped by gene-by-environment interactions. These loci can potentially serve as candidates for studies of adaptive seed size variation in wild grass species. Key words: grain size, genome-wide association study (GWAS), General Linear Model (GLM), Mixed Linear Model (MLM), Oryza sativa, rice. La taille des graines est variable chez de nombreuses especes vegetales et comprendre les facteurs genetiques qui sous-tendent cette variation peut fournir un eclairage sur les mecanismes d'adaptation aux conditions locales. Dans ce travail, les auteurs emploient les abondantes ressources genomiques et genetiques disponibles chez le riz (Oryza sativa) pour realiser une analyse d'association pan-genomique (GWAS) a grande echelle sur la largeur des graines. La largeur des graines varie grandement au sein de cette espece et presente une variation associee au climat parmi les populations du riz sauvage. A l'aide d'un jeu filtre de >1,9 million de marqueurs SNP a travers le genome chez 570 accessions de riz cultive et sauvage, les auteurs ont realise un GWAS a l'aide de deux modeles complementaires, GLM et MLM. Les modeles ont livre 10 et 33 associations significatives, respectivement, et ont conjointement revele sept regions candidates, dont deux avaient ete identifiees precedemment. Des analyses de la diversite nucleotidique et de la distribution des haplotypes a ces locus ont revele des signatures de selection et une structure suggerant une introgression adaptative d'alleles pour la largeur des graines parmi les differents groupes du riz. Ces resultats augmentent de 50% le nombre total de locus pour la largeur des graines chez le riz et supportent un modele polygenique ou la largeur des grains est determinee par des interactions gene-environnement. Ces locus pourront possiblement servir de candidats pour de futures etudes sur la variation adaptative au sein des especes sauvages de graminees. [Traduit par la Redaction] Mots-cles: taille des graines, analyse d'association pan-genomique (GWAS), modele lineaire general (GLM), modele lineaire mixte (MLM), Oryza sativa, riz.

Four new 2-pyrone derivatives, two pairs of enantiomers, (±)-egypyrone A [(±)-1] and (±)-egypyrone B [(±)-2], together with a new benzophenone analogue, orbiophenone B (3), were isolated from the endophytic fungus Penicillium egyptiacum. The enantiomeric mixtures (±)-1 and (±)-2 were separated through chiral HPLC, respectively. Their structures were elucidated by extensive analysis of spectroscopic data and the absolute configuration was determined by comparing the optical rotation of structurally similar molecule. Subsequently, the cytotoxic activities of (±)-1, (±)-2, and 3 against the U87 cell line were tested and no activity was observed at a concentration of 10 µM. [ABSTRACT FROM AUTHOR]

Use of an artificial neural network (ANN) has been previously shown to be an effective tool in compensating scatter and crosstalk from the primary photons in simultaneous dual radionuclide imaging. Generally, a large number of input energy windows are required within the network structure while the commercial cameras have only 3-8 energy windows. It is difficult to use two input windows within the ANN structure for the crosstalk contamination corrections of [sup.99m]Tc/[sup.123]I images acquired using only two photopeak energy windows. In this paper, we designed an ANN network with 24 inputs, 32 nodes in the hidden layer and two nodes in the output layer, to correct for crosstalk contamination in [sup.99m]Tc/[123.sup.I] images acquired using two photopeak windows. We trained the network using experimentally acquired [sup.99m]Tc and [sup.123]I spectrum data using the RSD brain phantom. The neural network package Stuttgart Neural Network Simulator (SNNSv4.2), from the University of Stuttgart, was used for the neural network training and the crosstalk corrections. Two sets of image data were tested. The first was a human activation study and the other used a cylindrical striatal phantom. Our results show a great improvement on both the human activation and the cylindrical striatal phantom images. Further work is to test our new approach on more [sup.99m]Tc/[sup.123]I imaging data and apply it to other radionuclide combinations such as [sup.201]Tl/[sup.99m]Tc. Index Terms--Artificial neural network (ANN), crosstalk contamination, dual radionuclide imaging.