Integration of foreign genes into plant genomes by the Agrobacterlum T-DNA transfer system has been considered to occur at random. It has been speculated that the chromosomal structure of the integration site might affect the expression pattern of the introduced genes. To gain insight into the molecular structure of T-DNA integration sites and its possible impact on gene expression, we have examined plant DNA sequences In the vicinity of T-DNA borders. Analysis of a transgenic petunia plant containing a chloramphenicol acetyltransferase (CAT) gene regulated by the hemoglobin promoter (PAR) from Parasponia andersonii revealed a scaffold attachment region (SAR) close to one T-DNA end. In addition to having strong binding affinities for both animal and plant nuclear scaffolds this petunia SAR element is as active in mammalian cells as the authentic elements from mammalian sources.

We determined the nucleotide sequence of gene 1 of Klebsiella phage K11, which is a member of the T7 group of phages. The largest open reading frame corresponds to a polypeptide with 906 amino acids and a molecular weight of 100,383 daltons. The deduced amino acid sequence of this polypeptide shows 71% homology to the T7 RNA polymerase (the product of T7 gene 1), 72% homology to the T3 RNA polymerase and 27% homology to the SP6 RNA polymerase. Divergent evolution was clearly most pronounced in the amino-terminal portion.

The epidermis has been considered the site of auxin action on elongation of stems and coleoptiles. To try to identify mRNAs that might mediate auxin stimulation of cell enlargement, we compared, using in vitro translation assays, mRNA enhancement by indoleacetic acid (IAA) in the epidermis, with that in the internal tissues, of pea (Pisum sativum L., cv Alaska) third internode segments. We used seedlings that had been grown under red light, which enables the epidermis to be peeled efficiently from the internode. Most of the 'early' IAA enhancements previously reported using etiolated peas, plus several hitherto undescribed enhancements, occur in both the epidermis and the intemal tissue of the light-grown plants after 4 hours of IAA treatment. These enhancements, therefore, do not fulfill the expectation of elongation-specific mRNAs localized to the epidermis. One epidermisspecific IAA enhancement does occur, but begins only subsequent to 1 hour (but before 4 hours) of auxin treatment. Similarly, the previously mentioned IAA enhancements common to epidermis and intemal tissue do not begin, in the light-grown plants, within 1 hour of IAA treatment. Since IAA stimulates elongation in light-grown intemodes within 15 minutes, it appears that none of these mRNAs can be responsible for auxin induction of elongation. We confirmed, with our methods, the previous reports that some of these mRNAs are enhanced by IAA within 0.5 hour in etiolated internodes. This indicates that we could have detected an early enhancement in light-grown tissue had it occurred.A number of reports indicate that auxins such as IAA can induce rapid increases in the levels of certain mRNAs (reviewed in 3, 4, 8, 9, 20). Most of these publications suggest that some of the early-enhanced mRNAs may be responsible for the stimulation of cell elongation by auxins. However, the actual function of none of the rapidly auxin-enhanced mRNAs has as yet been determined.

Variability of expression of introduced marker genes was analysed in a large number of tobacco regenerants from an Agrobacterium-mediated transformation. In spite of standardization of sampling, considerable variation of GUS and NPTII expression was observed between individual transformants at different times of analysis and in different parts of the same plant. Organ-specificity of root versus leaf expression conferred by the par promoter from the haemoglobin gene of Parasponia andersonii in front of the gus gene showed a continuous spectrum. GUS expression in roots was found in 128 out of 140 plants; expression in leaves was found in 46 plants, and was always lower than in the corresponding roots. NPTII expression regulated by the nos promoter also showed a continuous spectrum. Expression levels were generally higher in roots than in leaves. Plants with high GUS expression in leaves showed high NPTII activity as well. A positive correlation between the level of NPTII expression and the numbers of integrated gene copies was noted. Chromosomal position effects and physiological determination are suggested as triggers for the variations. The transformed regenerated tobacco plants were largely comparable to clonal variants.

SUMMARYThe phylogenetic relationship between Klebsiella phage No. 11 and the classical coilphages T7 and T3, postulated in a previous study, was investigated at the nucleotide level by sequencing the termini of phage No. 11 DNA. This DNA was found to have a terminal redundancy of 181 base pairs. Comparison of the terminal sequences of T7, T3 and No. 11 DNA suggests that the terminal redundancies of the three phages contain different expansions and variations of the short "founder sequence' 5' TTAACCTTGGG 3' of a common ancestor.In a previous study (Korsten et al., 1979) we reported evidence that the capsule-specific Klebsiella phage No. 11 (henceforth called K 11) is distantly related to the classical coliphages T3 and T7. This evidence was based mainly on the fact that phage K11, like T3 and T7, codes for an early protein of molecular weight about 100000 which shows an RNA polymerase activity specific for promoters located on the phage genome and not found on the DNA of the host. However, the template specificity of the phage K11 polymerase was totally different from that of T3 or T7: the RNA polymerases of these phages did not transcribe phage K11 DNA to any extent, and vice versa. (This is in contrast to the 20 to 50% heterologous transcriptional activity found upon comparing the RNA polymerases ofT3 and T7.) No compelling evidence for a phylogenetic common origin of phages K11 on the one hand, and T3 and T7 on the other, was provided by other criteria, since the first showed no serological crossreactions with the latter and K11 DNA did not efficiently form heteroduplexes with DNA ofT3 or T7. Also, a comparison of the electrophoretic patterns of Kll-coded intracellular proteins with those of T7 revealed marked differences in the molecular weights of most proteins; thus, only a few of these could be considered obviously homologous (Korsten et al., 1979). We undertook the present study with the aim of clarifying, at the nucleotide level, the putative phylogenetic relationship of phage K 11 with phages T3 and T7 by sequencing the termini of K I 1 DNA. Our results show that this phage has a characteristic terminal redundancy (TR) which we have compared to the known sequences of the TR of T7 (Moffat et al