Further ALK5 Inhibitor II analysis using antibodies to the Gr68a protein or a mutant in the gene will be needed. In any case, the robust expression of this GAL4 line stimulated us to uncover a novel role of mechanosensation in courtship initiation. In this study, we, for the first time, found that acoustic signals provided by active females stimulate fast localization of the female for courtship initiation. This stimulation of initiation is likely to be due to a change in the attentional state of the male, since noises emitted by either male and female flies or even white noise enhanced initiation. If noise makes the male more alert, he is likely to move around the chamber and to encounter and sense the silent female. TNT/Gr68a males failed to detect movement signals and had delayed courtship initiation, suggesting that neural function of Gr68a-mechanosensory Dinaciclib organs was required for signal detection. However, it is not clear yet whether the signal is transmitted through air as an acoustic signal or as a seismic signal propagating via the chamber floor. The intense expression of Gr68a-GAL4 in Johnston��s organ and AMMC strongly suggests that the auditory system is blocked in the mutant males. Supporting this possibility, an auditory mutant, 5D10 showed delayed courtship initiation in dark. The failure of truncation of the aristae to decrease courtship latency, however, suggests that there may be contributions from other mechanosensory organs to the noisedependent increase in attention which enhances courtship initiation. Further analysis will be needed to determine whether the mechanosensory system that increases arousal employs an arista-antenna-rotation mechanism as in courtship song detection, or a footstep-sound-transmitted-as-floor-vibration mechanism as do crickets or spiders. A 4 or 5-day-old male was placed with a decapitated female ����courtship object���� in a single-pair-mating chamber and its courtship performance was videotaped with a digital camcorder for 10 min. A courtship index was calculated as the proportion of time a male displayed courtship action during the 10 min observation period. Courtship latency was the time lag to the first courtship display after pairing. A latency value of 600 sec was recorded when no courtship was performed during the 10 min observation. Bout duration is the mean duration of each consecutive courtship sequence between breaks. $20 males were tested for each genotype. For courtship conditioning, a male was put together with a trainer female, either an immature female or a decapitated mature virgin for 60 min. Immediately after training, males were transferred into a clean chamber and paired with a decapitated mature female ��tester�� for 10 min.