Rice MicroRNA Effector Complexes and Targets[C][W]

MicroRNAs (miRNAs) are small silencing RNAs with regulatory roles in gene expression. miRNAs interact with Argonaute (AGO) proteins to form effector complexes that cleave target mRNAs or repress translation. Rice (Oryza sativa) encodes four AGO1 homologs (AGO1a, AGO1b, AGO1c, and AGO1d). We used RNA interference (RNAi) to knock down the four AGO1s. The RNAi lines displayed pleiotropic developmental phenotypes and had increased accumulation of miRNA targets. AGO1a, AGO1b, and AGO1c complexes were purified and further characterized. The three AGO1s all have a strong preference for binding small RNAs (sRNAs) with 5′ U and have Slicer activity. We cataloged the sRNAs in each AGO1 complex by deep sequencing and found that all three AGO1s predominantly bound known miRNAs. Most of the miRNAs were evenly distributed in the three AGO1 complexes, suggesting a redundant role for the AGO1s. Intriguingly, a subset of miRNAs were specifically incorporated into or excluded from one of the AGO1s, suggesting functional specialization among the AGO1s. Furthermore, we identified rice miRNA targets at a global level. The validated targets include transcription factors that control major stages of development and also genes involved in a variety of physiological processes, indicating a broad regulatory role for miRNAs in rice

Copper-Catalyzed Regioselective Intramolecular Electrophilic Sulfenoamination via Lewis Acid Activation of Disulfides under Aerobic Conditions

The activation of disulfides by Cu­(II) salts has been realized, which triggers a highly efficient electrophilic sulfenoamination of alkenes under aerobic conditions. Various sulfenyl N-heterocycles and their Selena counterparts were produced regioselectively, with no competing disulfidation products detected. Mechanistic studies suggest a profound influence of the counterions on the Lewis acidic copper center, and the important roles of oxygen and DMSO as co-oxidants for these cyclization processes

Iron-Catalyzed Regiospecific Intermolecular Radical Cyclization of Anilines: Strategy for Assembly of 2,2-Disubstituted Indolines

The first regiospecific catalytic intermolecular assembly of 2,2-disubstituted indolines has been developed. This protocol is based on a ligand and directing group free, iron-catalyzed radical [3 + 2] process, allowing efficient coupling of different <i>N</i>-sulfonylanilines with various α-substituted styrenes. Preliminary mechanistic studies elucidated the radical mechanism involving a reactive and versatile anilino radical and the importance of iron complex as a Lewis acid, rendering both the reactivity and regiospecificity of this transformation