The tobacco bZIP transcription factor BZI-1 binds to G-box elements in the promoters of phenylpropanoid pathway genes in vitro, but it is not involved in their regulation in vivo

Screening of a tobacco (Nicotiana tabacum) cDNA library resulted in the isolation of a clone encoding the bZIP transcription factor BZI-1. With respect to amino acid sequence, conservation of protein domains, genomic exon-intron structure and expression pattern, BZI-1 is closely related to CPRF2, OHP1/2, BLZ1 and REB, a group of bZIP proteins which have been described in a number of dicot and monocot species. BZI-1 exhibits the characteristics of a transcription factor. It binds to G-box and C-box cis-elements in vitro, it is localised in the nucleus, and the N-terminal region of BZI-1 functions as an activation domain in both yeast and plant cells. Since BZI-1-related transcription factors have been isolated from dicots by in vitro binding to G-box elements in the chalcone synthase ( CHS) promoter, it has been suggested that phenylpropanoid pathway genes, such as CHS and PAL (phenylalanine ammonia-lyase), are targets of these proteins in vivo. However, after infection with Pseudomonas syringae or Tobacco Mosaic Virus, no changes in pathogen-induced PAL expression were observed in transgenic plants expressing increased levels of BZI-1 or a dominant negative form of the protein, BZI-1-DeltaN. In contrast to the tissue-specific expression of CHS and PAL, BZI-1 was found to be ubiquitously expressed in tobacco plants. Furthermore, no changes in the tissue-specific expression of PAL or CHS were observed in plants that were transgenic for BZI-1-DeltaN. Expression of a VP16-BZI-1 fusion protein would be expected to result in constitutive activation of the BZI-1 target genes. However, tetracycline-dependent expression of a VP16-BZI-1 protein in tobacco plants did not result in activation of CHS or PAL. On the basis of these data, we conclude that the phenylpropanoid pathway genes analysed are not targets of BZI-1 in vivo. Thus, the pattern of in vitro DNA binding of transcription factors need not always reflect their in vivo function.

Influence of age and presbyacusis on DPOAE

The influence of presbyacusis on distortion-product otoacoustic emissions (DPOAEs) was studied on 180 ears of 96 normal-hearing subjects. The subjects' ages were distributed equally and ranged from 14 to 82 years. It was shown that there is a highly significant decrease in DPOAE amplitudes during the ageing process. By means of special statistical procedures, such as partial correlation and multiple regression, it was proved that the main reason for this is deterioration in pure-tone thresholds. However, other age-related effects were determined and were also found to lead to a further decrease in DPOAE amplitudes. The latter might be due to middle ear alterations in elderly people. Knowledge of the influence of presbyacusis on DPOAE is important if DPOAEs are to be used in expert assessment of inner ear disorders, for example, occupational noise-induced hearing loss.

In situ investigation of laser ablation

The complex system of in situ diagnostic methods such as SEM, ballistic microbalance, electric probe and high speed photography is necessary for measurement of basic parameters of laser target interaction. Only the knowledge of these basic parameters allows the discussion of microscopical processes on the target surface by laser irradiation. The results are discussed for our synchronised double laser system and for aluminium target. The mass relation of atoms, ions and droplets emitted by the target was determined. This relation is the base of a complete energy balance of laser target interaction.