A dynein-associated photoreceptor protein prevents ciliary acclimation to blue light.

Light-responsive regulation of ciliary motility is known to be conducted through modulation of dyneins, but the mechanism is not fully understood. Here, we report a novel subunit of the two-headed f/I1 inner arm dynein, named DYBLUP, in animal spermatozoa and a unicellular green alga. This subunit contains a BLUF (sensors of blue light using FAD) domain that appears to directly modulate dynein activity in response to light. DYBLUP (dynein-associated BLUF protein) mediates the connection between the f/I1 motor domain and the tether complex that links the motor to the doublet microtubule. Chlamydomonas lacking the DYBLUP ortholog shows both positive and negative phototaxis but becomes acclimated and attracted to high-intensity blue light. These results suggest a mechanism to avoid toxic strong light via direct photoregulation of dyneins.

Mutations in PIH proteins MOT48, TWI1 and PF13 define common and unique steps for preassembly of each, different ciliary dynein.

Ciliary dyneins are preassembled in the cytoplasm before being transported into cilia, and a family of proteins containing the PIH1 domain, PIH proteins, are involved in the assembly process. However, the functional differences and relationships between members of this family of proteins remain largely unknown. Using Chlamydomonas reinhardtii as a model, we isolated and characterized two novel Chlamydomonas PIH preassembly mutants, mot48-2 and twi1-1. A new allele of mot48 (ida10), mot48-2, shows large defects in ciliary dynein assembly in the axoneme and altered motility. A second mutant, twi1-1, shows comparatively smaller defects in motility and dynein assembly. A double mutant mot48-2; twi1-1 displays greater reduction in motility and in dynein assembly compared to each single mutant. Similarly, a double mutant twi1-1; pf13 also shows a significantly greater defect in motility and dynein assembly than either parent mutant. Thus, MOT48 (IDA10), TWI1 and PF13 may define different steps, and have partially overlapping functions, in a pathway required for ciliary dynein preassembly. Together, our data suggest the three PIH proteins function in preassembly steps that are both common and unique for different ciliary dyneins.

Selective Long-Distance Isomerization of Terminal Alkenes via Nondissociative Chain Walking.

Selective long-distance isomerization of terminal alkenes to silyl enol ethers proceeded via nondissociative chain walking using phenanthroline palladium catalysts. Notable features achieved taking advantage of the nondissociative chain walking mechanism include high efficiency obtained regardless of the chain length, high chemoselectivity toward terminal alkenes over internal ones, and retention of the stereoconfiguration of the stereocenter on the alkyl chain.