An HR-induced tobacco peroxidase gene is responsive to spermine, but not to salicylate, methyl jasmonate, and ethephon.

In Tobacco mosaic virus (TMV)-infected tobacco plants carrying the N resistance gene, a hypersensitive reaction or response (HR) occurs to enclose the virus in the infected tissue. Although a contribution of peroxidases to the resistance has been proposed, no evidence has been presented that tobacco peroxidase genes respond to HR. Here, we describe the HR-induced expression of a tobacco peroxidase gene (tpoxC1) whose induction kinetics were slightly different from those of acidic and basic tobacco pathogenesis-related (PR) protein genes. Interestingly, tpoxC1 was insensitive to the inducers of PR genes such as salicylic acid, methyl jasmonate, and ethephon. Spermine activated tpoxC1 gene expression at a low level and both acidic and basic PR gene expression at a considerably higher level. These results indicate that the induced expression of tpoxC1 is regulated differently from that of classical tobacco PR genes in the N gene-mediated self-defense system in tobacco plants.

The modular structure and function of the wheat H1 promoter with S phase-specific activity.

Two histone H1 genes, TH315 and TH325, were isolated from a wheat genomic library. Nucleotide sequence analysis and comparison with other histone gene promoters revealed that the promoters of both genes contain many characteristic motifs conserved among plant histone H1 genes. They are 6 novel short stretches, named CS1 to CS6, and already documented elements or their relatives such as Oct, Oct-like (OLS), Nona-like (NonaLS), CCAAT box, and TATA box. Transient expression experiments with the TH315 promoter/GUS chimeric gene and its mutagenized derivatives showed that two Oct motifs, OLS, and CCAAT box are positive cis-acting elements. NonaLS and CS4 were suggested to be positive cis-acting elements and CS5 and CS6 to be negative elements. An Oct motif and CCAAT box constitutes a type III element and the 202-bp sequence containing these elements from -128 to +74 of the TH315 gene was shown to be sufficient to confer S phase-specific expression. The type III element is found in all plant histone H1 and H2B genes, suggesting that it is a subtype-specific element. Most plant histone genes have one of the type I, II, and III elements. We propose to classify the plant histone genes into three classes, based on the context of Oct in the promoters.

The conserved 3'-flanking sequence, AATGGAAATG, of the wheat histone H3 gene is necessary for the accurate 3'-end formation of mRNA.

We examined the 3'-flanking regions required for accurate 3'-end formation of wheat histone H3 mRNA using gene expression in transformed sunflower cells. The introduction of mutations into the conserved sequence AATGGAAATG in the 3'-flanking region of plant histone genes, located 22 bp upstream from the polyadenylation site of the wheat H3 gene (TH012), completely abolished the 3'-end formation of mRNA at the authentic 3' end without affecting the transcription efficiency. However, a 0.8 kbp sequence containing this motif could not produce a normal 3' end when joined to the 3' end of the nopaline synthase (NOS) gene instead of its 3' sequence. The results indicated that this conserved sequence is necessary but not sufficient for the 3'-end formation of H3 or NOS mRNA. Deletion of a 59 bp sequence, located 19 bp upstream from the AATGGAAATG sequence, also reduced the 3'-end formation efficiency by a factor of 10, compared with the efficiency in wild-type gene. We concluded that 3'-end formation of wheat histone H3 mRNA is regulated by multiple sequences including the AATGGAAATG motif.

Proximal promoter region of the wheat histone H3 gene confers S phase-specific gene expression in transformed rice cells.

The cis-regulatory elements that confer cell cycle-dependent expression to the wheat histone H3 gene were investigated in rice cells (Oc strain) transformed with H3/GUS chimeric genes. 5' deletion mutants of the H3 promoter region (from -1711, -908 or -185 to +57 relative to the transcription start site) were joined to the coding sequence of the bacterial beta-glucuronidase (GUS) gene then introduced stably into rice cells. S1 analyses of the RNA from transformed rice cells whose cell cycles had been synchronized by treatment with aphidicolin showed that the steady-state levels of the transcripts from chimeric genes were altered with the change in DNA synthesis and the content of rice H3 mRNA throughout the cell cycle. Even though H3 promoter activity decreased as 5' deletion proceeded, transcripts from the chimeric genes showed increases, as much as 10-fold 1 h after release from the aphidicolin block, which were rapidly lost over the next 4 h. The results suggest that the 242 bp sequence from -185 to +57, which contains the basal promoter region, confers the S phase-specific expression of the H3 gene and that the upstream sequence from position -186 is required for the full activity of this promoter.

Cell cycle-regulated gene expression in transgenic plant cells.

A majority of histone genes are expressed in the S phase during the cell cycle. Using the gene expression system of transformed sunflower cells into which wheat histone H3 gene was introduced by the Ti-plasmid gene transfer technique, we determined three cis-acting control sequences (hexameric, octameric, and nonameric motifs) which seemed to confer the S-phase-specific transcription of wheat histone genes. Furthermore, as candidates for regulatory transcription factors, three nuclear DNA-binding proteins HBP-1a, HBP-1b, and HBP-2 that interact with the hexameric and nonameric motifs were identified. The structural analysis of the cDNA of HBP-1a revealed that a nuclear protein has the leucine-zipper structure and a DNA-binding motif. The hexameric motif in the H3 gene was also seen in cauliflower mosaic virus 35S (CaMV 35S) promoter and shown to function as a regulatory element of this promoter. The wheat HBP-1b can interact with the hexameric motif of the CaMV 35S promoter. Much attention has been paid to the significance of the hexameric sequences within the H3 and CaMV 35S promoters and the DNA-binding proteins HBP-1a and HBP-1b.

Effects of nicardipine and other Ca2+-antagonists on catecholamine transport into chromaffin granule membrane vesicles.

Nicardipine (10(-7)-2 X 10(-5) M) inhibited the transport of noradrenaline into chromaffin granule membrane vesicles in a concentration-dependent manner. This inhibitory effect of nicardipine was found to be appreciably stronger than that of other Ca2+-antagonists(diltiazem, nifedipine and verapamil) and was not due to the blockade of Ca2+-channel in the granule membranes.