The R2R3 MYB transcription factor C1 requires the basic helix-loop-helix factor R as an essential co-activator for the transcription of maize anthocyanin genes. In contrast, the R2R3 MYB protein P1 activates a subset of the C1-regulated genes independently of R. Substitution of six amino acids in P1 with the C1 amino acids results in P1*, whose activity on C1-regulated and P1-regulated genes is R-dependent or R-enhanced, respectively. We have used P1* in combination with various promoters to uncover two mechanisms for R function. On synthetic promoters that contain only C1/P1 binding sites, R is an essential co-activator of C1. This function of R is unlikely to simply be the result of an increase in the C1 DNA-binding affinity, since transcriptional activity of a C1 mutant that binds DNA at a higher affinity, comparable with P1, remains R-dependent. The differential transcriptional activity of C1 fusions with the yeast Gal4 DNA-binding domain in yeast and maize cells suggests that part of the function of R is to relieve C1 from a plant-specific inhibitor. A second function of R requires cis-regulatory elements in addition to the C1/P1 DNAbinding sites for R-enhanced transcription of a1. We hypothesize that R functions in this mode by binding or recruiting additional factors to the anthocyanin regulatory element conserved in the promoters of several anthocyanin genes. Together, these findings suggest a model in which combinatorial interactions with co-activators enable R2R3 MYB factors with very similar DNA binding preferences to discriminate between target genes in vivo.Flowering plants express a large number of proteins containing the conserved R2R3 MYB DNA-binding domain. About 125 R2R3 Myb genes are present in the Arabidopsis genome (1), and many more are predicted to be expressed in maize and related monocots (2, 3). Similar to other transcription factor families, the R2R3 MYB factors show exquisite regulatory specificity in vivo, while recognizing very similar DNA sequences in vitro (4 -9). Thus, mechanisms other than discrimination between similar DNA-binding sites are at play in the control of specific sets of target genes by each R2R3 MYB transcription factor in vivo.The regulation of flavonoid biosynthetic gene expression by the cooperation of R2R3 MYB and basic helix-loop-helix (bHLH)1 transcription factors provides one of the best described examples of combinatorial gene regulation in plants (10,11). Anthocyanin accumulation in maize is controlled by two classes of regulatory proteins that act in concert: C1 or PL1, two closely related R2R3 MYB domain proteins (12), and R or B, which are members of the R/B family of bHLH domain proteins (13). Extensive genetic and molecular studies have shown that the C1 or Pl1 genes require a member of the bHLH-containing R or B gene family to activate transcription of the anthocyanin biosynthetic genes (10). The C1-and R/Bencoded proteins physically interact, and this interaction is mediated by the MYB domain of C1 and the N-terminal region of B (14) or R (15).The m...

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In this paper, we introduce a method to overcome the limitation of thickness measurement of a micro-patterned thin film. A spectroscopic imaging reflectometer system that consists of an acousto-optic tunable filter, a charge-coupled-device camera, and a high-magnitude objective lens was proposed, and a stack of multispectral images was generated. To secure improved accuracy and lateral resolution in the reconstruction of a two-dimensional thin film thickness, prior to the analysis of spectral reflectance profiles from each pixel of multispectral images, the image restoration based on an iterative deconvolution algorithm was applied to compensate for image degradation caused by blurring.

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This research introduces an improved version of a spectroscopic imaging reflectometer to secure reliable measurement performance in the reconstruction of spatially resolved thin film thickness. Due to its simple structure, the rotating-type filter has the advantage of robustness, but it has a limitation of spectral resolution. To improve the spectral resolution, a multi-reflectance method was applied. The angle of incidence can be adjusted by changing the diameter of the tunable aperture. By combining multiple spectral reflectance signals obtained at different incident angles, one integrated signal with improved spectral resolution can be obtained. The effect of the improved spectral resolution on the measurement performance was evaluated.