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Studies have indicated that exon and intron size and intergenic distance are correlated with gene expression levels and expression breadth. Previous reports on these correlations in plants and animals have been conflicting. In this study, next-generation sequence data, which has been shown to be more sensitive than previous expression profiling technologies, were generated and analyzed from 14 tissues. Our results revealed a novel dichotomy. At the low expression level, an increase in expression breadth correlated with an increase in transcript size because of an increase in the number of exons and introns. No significant changes in intron or exon sizes were noted. Conversely, genes expressed at the intermediate to high expression levels displayed a decrease in transcript size as their expression breadth increased. This was due to smaller exons, with no significant change in the number of exons. Taking advantage of the known gene space of soybean, we evaluated the positioning of genes and found significant clustering of similarly expressed genes. Identifying the correlations between the physical parameters of individual genes could lead to uncovering the role of regulation owing to nucleotide composition, which might have potential impacts in discerning the role of the noncoding regions. Key words: expression level, expression breadth, next-generation sequencing, physical clustering. Des etudes ont montre que la taille des introns et des exons ainsi que la distance intergeenique seraient corretees avec le niveau et l'etendue de l'expression geenique. Les etudes anteerieures sur ce sujet chez les plantes et les animaux se sont averees contradictoires. Dans cette etude, des domtoes de sequence de seconde generation, lesquelles fournissent des donnees transcriptomiques plus sensibles que celles obtenues a l'aide des techniques anteerieures, ont ete produites et analysees chez 14 tissus. Les resultats des auteurs revelent une nouvelle dichotomie. Chez les genes faiblement exprimes, un accroissement de l'etendue de l'expression etait correle avec un accroissement de la taille des transcrits attribuable a une augmentation du nombre d'exons et d'introns. Aucun changement quant a la taille des introns ou des exons n'a ete note;. Inversement, les genes exprimes de maniere intermeidiaire ou forte presentaient des transcrits dont la taille diminuait au fur et a mesure que s'accroissait l'etendue de leur expression. Cette reduction etait due a une reduction de la taille des exons, sans qu'il y ait eu reduction du nombre de ceux-ci. En tirant avantage de la connaissance de l'espace geenique chez le soya, les auteurs ont examine; le positionnement des genes et ont observe un groupement significatif des genes qui presentent un niveau d'expression semblable. L'identification de correlations entre les parameitres physiques de genes individuels pourrait permettre de mieux comprendre la re;gulation ge;nique de;coulant de la composition nucle;otidique, laquelle pourrait aider a discerner le role des regions non-codantes. Mots-cles: niveau d'expression, eetendue de l'expression, seequencage de seconde generation, groupement physique. [Traduit par la Redaction], Introduction The uniqueness of living organisms is dependent not only upon the suite of genic material available to them but also upon the subtleties of gene expression patterns. Some genes [...]

We have previously shown that linkage disequilibrium (LD) in the elite cultivated barley (Hordeum vulgare) gene pool extends, on average, for Key words: barley, SNP, linkage disequilibrium, association mapping. Resume : Les auteurs ont montre precedemment que le desequilibre de liaison chez les orges cultivees (Hordeum vulgare) elites s'etend en moyenne sur une distance de 1-5 cM. Sur la base de cette information, les auteurs ont mis au point une plateforme pour les analyses d'association qui comprend une collection d'environ 1000 lignees elites qui ont ete caracterisees a 3060 locus polymorphismes mononucleotidiques (SNP) distribues dans le genome. L'examen de ce jeu de donnees a revele qu'une structuration significative de la population existe au sein de ce materiel elite et que la diversite et le LD varient considerablement sur l'ensemble des sept chromosomes de l'orge. Cependant, les auteurs montrent egalement que la sous-population composee uniquement des orges de printemps a deux rangs est moins structuree et se prete bien aux analyses de balayage genomique sans necessiter d'importantes interventions statistiques visant a tenir compte de la structure. A la presente densite de marqueurs, la population d'orges de printemps a deux rangs se prete bien a la cartographie fine de caracteres simples qui sont situees en dehors des regions centromeriques avec une resolution qui est suffisante pour identifier des genes candidats sur la base de la syntenie conservee avec les genomes modeles completement sequences ainsi que la carte physique en developpement chez l'orge. Mots-cles: orge, SNP, desequilibre de liaison, analyse d'association., [Traduit par la Redaction] Introduction Genome-wide association studies are commonplace in the search for genes controlling human genetic disorders, but are in their infancy in plant genetic research, particularly in [...]

Previous studies have shown that there is considerable population structure in cultivated barley (Hordeum vulgare Lo), with the strongest structure corresponding to differences in row number and growth habit. U.S. barley breeding programs include six-row and two-row types and winter and spring types in all combinations. To facilitate mapping of complex traits in breeding germplasm, 1816 barley lines from 10 U.S. breeding programs were scored with 1536 single nucleotide polymorphism (SNP) genotyping assays. The number of SNPs segregating within breeding programs varied from 854 to 1398. Model-based analysis of population structure showed the expected clustering by row type and growth habit; however, there was additional structure, some of which corresponded to the breeding programs. The model that fit the data best had seven populations: three two-row spring, two six-row spring, and two six-row winter. Average linkage disequilibrium (LD) within populations decayed over a distance of 20 to 30 cM, but some populations showed long-range LD suggestive of admixture. Genetic distance (allele-sharing) between populations varied from 0.11 (six-row spring vs. six-row spring) to 0.45 (two-row spring vs. six-row spring). Analyses of pairwise LD revealed that the phase of allelic associations was not well correlated between populations, particularly when their allele-sharing distance was >0.2. These results suggest that pooling divergent barley populations for purposes of association mapping may be inadvisable. doi: 10.2135/cropsci2009.04.0198

Restoration of native plant communities requires adapted germplasm; thus, information is needed to guide native seed collection and production. Analysis of genetic variation has potential to provide insight into diversity and relatedness of natural populations. Our objectives were to examine genetic diversity of native species in Minnesota to discover if variation is related to biomes or distance, and possibly to develop seed collection zones. Our study included prairie cordgrass (Spartina pectinata), purple prairie clover (Dalea purpurea), and spotted joe-pye weed (Eupatorium maculatum). Using amplified fragment length polymorphisms, we analyzed 100 samples from eight populations for prairie cordgrass, 152 samples from nine populations for purple prairie clover, and 127 samples from 10 populations for spotted joe-pye weed. We found moderate to high levels of genetic diversity within each species. Small populations were not necessarily lower in diversity than larger ones. Analysis of molecular variance results indicate clear population differentiation. However, rather than displaying geographic or ecological associations, the variation had discontinuous patterns. Therefore, we were not able to develop unambiguous recommendations for seed collection. We discuss the applicability of molecular markers in detecting adaptive potential.

Wheat--barley chromosome addition lines are useful genetic resources for a variety of studies. In this study, transcript accumulation patterns in Betzes barley, Chinese Spring wheat, and Chinese Spring-Betzes chromosome addition lines were examined with the Barleyl Affymetrix GeneChip probe array. Of the 4014 transcripts detected in Betzes but not in Chinese Spring, 365, 271, 265, 323, 194, and 369 were detected in wheat--barley disomic chromosome addition lines 2(2H), 3(3H), 4(4H), 7(5H), 6(6H), and 1 (7H), respectively. Thus, 1787 barley transcripts were detected in a wheat genetic background and, by virtue of the addition line in which they were detected, were physically mapped to barley chromosomes. We validated and extended our approach to physically map barley genes to the long and short arms of chromosome 6 (6H). Our physical map data exhibited a high level of synteny with homologous sequences on the wheat and/or rice syntenous chromosomes, indicating that our barley physical maps are robust. Our results show that barley transcript detection in wheat--barley chromosome addition lines is an efficient approach for large-scale physical mapping of genes.

ragged seedling2 (rgd2) is a novel, recessive mutation affecting lateral organ development in maize. The mutant phenotype of homozygous rgd2-R leaves is variable. Mild leaf phenotypes have a reduced midrib and may be moderately narrow and furcated; severe Rgd2-[R.sup.-] leaves are filamentous or even radial. Despite their radial morphology, severe Rgd2-[R.sup.-] mutant leaves develop distinct adaxial and abaxial anatomical features. Although Rgd2-[R.sup.-] mutants exhibit no reduction in adaxial or abaxial cell types, areas of epidermal cell swapping may occur that are associated with misaligned vascular bundles and outgrowths of ectopic margins. Scanning electron microscopy of young primordia and analyses of leaf developmental-marker gene expression in mutant apices reveal that RGD2 functions during recruitment of leaf founder cells and during expansive growth of leaf primordia. Overall, these phenotypes suggest that development is uncoordinated in Rgd2-[R.sup.-] mutant leaves, so that leaf components and tissues may develop quasi-independently. Models whereby RGD2 is required for developmental signaling during the initiation, anatomical patterning, and lateral expansion of maize leaves are discussed. Keywords: Maize; Leaf development; SAM; Founder cells; Dorsiventral

Kernel color and grain protein concentration (GPC) are two of the most important attributes of barley (Hordeum vulgate L.) grain intended for use in malting and brewing. Grain with protein levels that are too low or high or that have dark kernel color, which may result from the disease complex of kernel discoloration (KD), is unacceptable for the malting and brewing industries. The purpose of this study was to use molecular markers to map quantitative trait loci (QTLs) for KD and GPC in two recombinant inbred line (RIL) populations. One population was created by means of the high GPC and KD resistant cultivar Chevron. The other population was created from a KD resistant cultivar MNBrite that was derived from Chevron through eight generations of crossing and selection for bright kernels. The traits KD and GPC were evaluated in four and three environments, respectively, using the Chevron population and six environments using the MNBrite population. GPC and KD score were negatively correlated in both populations. A revised genetic map for the Chevron/M69 population, with an additional 45 simple sequence repeat (SSR) markers, was used to identify nine QTLs associated with KD on chromosomes 1(7H), 2(2H), 4(4H), 6(6H), and 7(5H), including two major QTLs on chromosome 6(6H). A single QTL for GPC identified in the Chevron mapping population, accounting for over 55% of the phenotypic variation, was located on chromosome 6(6H) and was coincident with one of the two major QTLs for KD. In this region, the Chevron allele increased GPC and decreased KD score. In the MNBrite mapping population, the same region of chromosome 6(6H) was mapped with SSR markers, and QTL analysis verified that this region was associated with both KD and GPC, indicating that MNBrite inherited this region of chromosome 6(6H) from Chevron. The results of this study suggest that if GPC and KD are controlled by tightly linked genes, then it should be possible to use SSR markers to identify recombinants in this region of chromosome 6(6H) and break the linkage to allow selection for KD resistance without high GPC. Alternatively, if GPC and KD are conditioned by the same gene, then it should he possible to select for KID resistance from Chevron by means of SSR markers and to use phenotypic selection to introgress other genes to reduce GPC to acceptable levels., KERNEL COLOR AND GPC are two of the most important selection criteria for determining whether barley grain is of sufficient quality for malting and brewing. Kernel color is negatively affected [...]

Liguleless3-O (Lg3-O) transforms the leaf blade, auricle and ligule into sheath around the midrib region. We conducted a genetic mosaic analysis of the Lg3 phenotype to determine the site of Lg3 gene action. Combining the Mutator (Mu) suppressible Lg3-Or211 and a1-mum2 alleles in a Mu-active background generated a stock wherein somatic loss of Mu activity resulted in anthocyanin-marked clonal sectors expressing Lg3 in the leaf. Lg3-Or211 plants appear wild type in a Mu-active line, but Mu-inactive plants express a severe Lg3 phenotype. We observed four sector classes: wild type, sheath-like with ligule displacement, sheath-like with ectopic ligule, and auricle-like. The mutation does not cause transformation to a specific cell or regional identity. Lg3-Or211 activity in the mesophyll alters wild-type epidermal cell fates; activity in epidermis seems funtionless. Lg3 mutant activity has a nonautonomous, cell-layer-specific function in the transverse dimension. In the lateral dimension, sectors of Lg3 mutant phenotype can exhibit either cell-autonomous or nonautonomous effects. Our work demonstrates that mosaic analysis by coordinate suppression of Mu-induced alleles is useful for analyzing the cell autonomy of genetically defined functions.