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IntroductionCilia biogenesis relies on intraflagellar transport (IFT), a conserved transport mechanism which functions bi-directionally to bring protein complexes to the growing ciliary tip and recycle signaling and transport proteins between the cilium and cell body. InDrosophila, anterograde IFT is critical for assembly of sensory cilia in the neurons of both chordotonal (ch) organs, which have relatively long ciliary axonemes, and external sensory (es) organs, which have short axonemal segments with microtubules in distal sensory segments forming non-axonemal bundles. We previously isolated thebeethoven(btv) mutant in a mutagenesis screen for auditory mutants. Although manybtvmutant flies are deaf, some retain a small residual auditory function as determined both by behavior and by auditory electrophysiology. ResultsHere we molecularly characterize thebtvgene and demonstrate that it encodes the IFT-associated dynein-2 heavy chain Dync2h1. We also describe morphological changes in Johnston’s organ as flies age to 30 days, and we find that morphological and electrophysiological phenotypes in this ch organ ofbtvmutants become more severe with age. We show that NompB protein, encoding the conserved IFT88 protein, an IFT complex B component, fails to be cleared from chordotonal cilia inbtvmutants, instead accumulating in the distorted cilia. In macrochaete bristles, a class of es organ,btvmutants show a 50% reduction in mechanoreceptor potentials. DiscussionThus, thebtv-encoded Dync2h1 functions as the retrograde IFT motor in the assembly of long ciliary axonemes in ch organs and is also important for normal function of the short ciliary axonemes in es organs. 

In this paper we analyze a variant of the pursuit-evasion game on a graph $$G$$ where the intruder occupies a vertex, is allowed to move to adjacent vertices or remain in place, and is 'invisible' to the searcher, meaning that the searcher operates with no knowledge of the position of the intruder. On each stage, the searcher is allowed to inspect an arbitrary set of $$k$$ vertices. The minimum $$k$$ for which the searcher can guarantee the capture of the intruder is called the inspection number of $$G$$. We also introduce and study the topological inspection number, a quantity that captures the limiting behavior of the inspection number under subdivisions of $$G$$. Our central theorem provides a full classification of graphs with topological inspection number up to $$3$$.