Flowering time is a key life-history trait in the plant life cycle. Most studies to unravel the genetics of flowering time in Arabidopsis thaliana have been performed under greenhouse conditions. Here, we describe a study about the genetics of flowering time that differs from previous studies in two important ways: first, we measure flowering time in a more complex and ecologically realistic environment; and, second, we combine the advantages of genome-wide association (GWA) and traditional linkage (QTL) mapping. Our experiments involved phenotyping nearly 20,000 plants over 2 winters under field conditions, including 184 worldwide natural accessions genotyped for 216,509 SNPs and 4,366 RILs derived from 13 independent crosses chosen to maximize genetic and phenotypic diversity. Based on a photothermal time model, the flowering time variation scored in our field experiment was poorly correlated with the flowering time variation previously obtained under greenhouse conditions, reinforcing previous demonstrations of the importance of genotype by environment interactions in A. thaliana and the need to study adaptive variation under natural conditions. The use of 4,366 RILs provides great power for dissecting the genetic architecture of flowering time in A. thaliana under our specific field conditions. We describe more than 60 additive QTLs, all with relatively small to medium effects and organized in 5 major clusters. We show that QTL mapping increases our power to distinguish true from false associations in GWA mapping. QTL mapping also permits the identification of false negatives, that is, causative SNPs that are lost when applying GWA methods that control for population structure. Major genes underpinning flowering time in the greenhouse were not associated with flowering time in this study. Instead, we found a prevalence of genes involved in the regulation of the plant circadian clock. Furthermore, we identified new genomic regions lacking obvious candidate genes.

No abstract

N-Butyl N-carboxyanhydride (Bu-NCA) was polymerized in THF to produce poly(N-butylglycine) using benzyl alcohol initiator and 1,1,3,3-tetramethylguanidine (TMG) promoter. Poly(N-butylglycine) species (PNBG) with controlled molecular weight (M n = 2.9−20.5 kg mol −1 ) and narrow molecular weight distribution (PDI = 1.04−1.08) were obtained by controlling the initial monomer-to-initiator ratio and conversion. The reaction exhibits characteristics of a living polymerization, as evidenced by the linear increase of M n with conversion and successful chain extension experiments. Kinetic studies revealed a first-order dependence of propagation rate on the monomer and benzyl alcohol concentration and zero-order dependence on the TMG concentration, consistent with a controlled polymerization where the TMG does not influence the chain propagation. It was further revealed that the polymerization activities and M n control are strongly dependent on the structure of the alcohol initiators. Primary alcohols (e.g., methanol, ethanol, 2-methoxyethanol, npropanol, and benzyl alcohol) can mediate the polymerization of Bu-NCA with the TMG present to produce PNBG polymers with good to moderate control of M n s and PDIs. By contrast, sterically hindered secondary or tertiary alcohols (e.g., isopropyl alcohol and tert-butyl alcohol) or a primary alcohol bearing strongly electron withdrawing substituents (e.g., 2,2,2trifluoroethanol) or phenol either failed to initiate the polymerization or produced PNBGs whose molecular weights deviated to varying extents from the theoretical values based on single-site initiation with alcohols. 1 H NMR analysis revealed hydrogen bonding interactions between TMG and various alcohols, thereby promoting the initiation by enhancing the nucleophilicity of the alcohols toward ring-opening addition of Bu-NCA monomer. Electron-rich primary alcohols can initiate the polymerization more efficiently than the electron-deficient primary alcohol or sterically hindered secondary or tertiary alcohols, resulting in enhanced control over polymer molecular weight in the former than the latter. The polymerization has been successfully extended toward the synthesis of heteroblock copolymers based on poly(ethylene glycol) (PEG) and PNBG by using a hydroxylended PEG macroinitiator and TMG promoter.

No abstract

This paper describes how initial principles for the designs of an interactive application were informed from a study of 'coolness' with two different ages of teenagers. The study used drawings to examine how teenagers might design their environments and these were then analysed by the research team based on a set of characteristics of cool that were drawn from the literature. Results from the teenagers' drawings demonstrate some change in emphasis between the younger and older age groups and between the genders. A design space around innovation and rebellion is implicated in the findings.