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Abstract: Among the complete set of Arabidopsis ABC proteins, 15 correspond to the soluble or NBD-type (nucleotide binding domains). We have cloned cDNAs coding for three closely homologous NBD-like proteins, AtNAP2, AtNAP4 and AtNAP9 that display a characteristic ABC signature motif. In transitory expression assays, the three AtNAP proteins fused to the green-fluorescent protein (GFP) were localized in the cytosol of tobacco and Arabidopsis cell cultures. The expression of these genes is enhanced by 1% sucrose in the culture medium but not by non-assimilable sugars. This result was confirmed with an AtNAP2::GUS translational fusion derived from a promoter trap line in which the T-DNA is inserted near the 3′ end of the AtNAP2 coding sequence. According to the GUS staining, AtNAP2 is expressed in the elongation zone and meristem of roots of white light-grown seedlings and in the hypocotyl of dark-grown seedlings. We suggest that AtNAP2 might be involved in cell elongation processes. [Copyright &y& Elsevier]

Analysis of auditory scene relies on the appropriate division of the sensory input into meaningful events. The auditory system uses a sequential grouping strategy to segregate different acoustic events in the time domain. As a result of grouping, the organization of sound is expected to include acoustic events spanning different scales of time. It is unclear, however, at which moment the central auditory system begins to introduce changes in the neural representation of the auditory scene as a result of grouping different information units into a larger acoustic event. The present set of experiments examines this issue by using the mismatch negativity (MMN) component of event-related potentials. The MMN is elicited in response to changes in the previously registered auditory regularity whether or not the subject’s attention is focused on the auditory stimuli. By presenting three consecutive pairs of alternating tones in serial stimulus trains, we found that across-train repetitions of the tone elicited the MMN with inter-train intervals up to 240 ms. Beyond this interval, only within-train repetitions of the tone elicited the MMN, suggesting that pairs of tones were bound together into a single acoustic event (i.e., train of six tones) within a temporal window not much longer than 240 ms. Furthermore, a different pattern of responses was seen depending on the position of the deviant event within the train and the frequency distance between the alternating tones. These results suggest that grouping discrete auditory inputs may introduce changes in the neural representation of the auditory scene by applying rules to sounds spanning larger temporal scales. [Copyright &y& Elsevier]