A "mesmer"izing new approach to site-directed mutagenesis in large transformation-ready constructs: Mutagenesis via Serial Small Mismatch Recombineering

Diverse Roles of Axonemal Dyneins in Drosophila Auditory Neuron Function and Mechanical Amplification in Hearing

Much like vertebrate hair cells, the chordotonal sensory neurons that mediate hearing in Drosophila are motile and amplify the mechanical input of the ear. Because the neurons bear mechanosensory primary cilia whose microtubule axonemes display dynein arms, we hypothesized that their motility is powered by dyneins. Here, we describe two axonemal dynein proteins that are required for Drosophila auditory neuron function, localize to their primary cilia, and differently contribute to mechanical amplification in hearing. Promoter fusions revealed that the two axonemal dynein genes Dmdnah3 (=CG17150) and Dmdnai2 (=CG6053) are expressed in chordotonal neurons, including the auditory ones in the fly’s ear. Null alleles of both dyneins equally abolished electrical auditory neuron responses, yet whereas mutations in Dmdnah3 facilitated mechanical amplification, amplification was abolished by mutations in Dmdnai2. Epistasis analysis revealed that Dmdnah3 acts downstream of Nan-Iav channels in controlling the amplificatory gain. Dmdnai2, in addition to being required for amplification, was essential for outer dynein arms in auditory neuron cilia. This establishes diverse roles of axonemal dyneins in Drosophila auditory neuron function and links auditory neuron motility to primary cilia and axonemal dyneins. Mutant defects in sperm competition suggest that both dyneins also function in sperm motility.

An efficient method for recombineering GAL4 and QF drivers

Neural circuit mapping and manipulation are facilitated by independent control of gene expression in pre- and post-synaptic neurons. The GAL4/UAS and Q binary transcription systems have the potential to provide this capability. Of particular use in neural circuit mapping would be GAL4 and QF drivers specific for neurotransmitters and neurotransmitter receptors. Recently available Drosophila genomic BAC libraries make recombineering large genes including those specific for neurotransmitters and neurotransmitter receptors feasible. Here the functionality of cassettes that allow efficient recombineering of GAL4 and QF drivers based on kanamycin selection is demonstrated in Drosophila. The cassettes should, however, be generalizable for recombineering in other species.