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We present parallel algorithms for some fundamental problems in computational geometry which have running time of $O(logn)$ using $n$ processors, with very high probability (approaching 1 as $n~ \rightarrow~ \infty$). These include planar point location, triangulation and trapezoidal decomposition. We also present optimal algorithms for 3-D maxima and two-set dominance counting by an application of integer sorting. Most of these algorithms run on CREW PRAM model and have optimal processor-time product which improve on the previously best known algorithms of Atallah and Goodrich [3] for these problems. The crux of these algorithms is a useful data structure which emulates the plane sweeping paradigm used for sequential algorithms. We extend some of the techniques used by Reischuk [22] Reif and Valiant [21] for flashsort algorithm to perform divide and conquer in a plane very efficiently leading to the improved performance by our approach.

Young pine seedlings respond to environmental stress by induced synthesis of pinosylvin, a stilbene phytoalexin. Heartwood of pine trees is characterized by a high content of pinosylvin. The formation of pinosylvin from cinnamoyl-CoA and three molecules malonyl-CoA catalysed by pinosylvin synthase is typical of the genus Pinus. Its enzyme activity not detectable in unstressed seedlings is substantially increased upon application of stimuli like UV-light or infection with the phytopathogenic fungus Botrytis cinerea. A genomic DNA library was screened with pinosylvin synthase cDNA pSP-54 as a probe. Ten clones were isolated and grouped into five subclasses according to the size of their introns. After subcloning into plasmid T7T3, four different members of the five gene subclasses were characterized by sequencing. Emphasis was put on isolating various promoters and analyzing and comparing their responsiveness. The amino acid sequences deduced from genes PST-1, PST-2, PST-3 and PST-5 shared an overall identity of more than 95%. In gene PST-5, the putative translation start site ATG was replaced by CTG. While promoter regions near the TATAA box were almost identical PST-1, PST-2 and PST-3, further upstream sequences differed substantially. Differences in promoter strength were analysed both in transgenic tobacco plants and by transient expression in tobacco protoplasts. Constructs used contained the bacterial beta-glucuronidase under the control of the promoters of pine genes PST-1, PST-2 and PST-3. Upon treatment with UV light or fungal elicitor, the promoter of PST-1 showed highest responsiveness and led to tissue-specific expression in vascular bundles. The data suggest that in pine the gene product of PST-1 is responsible for both the stress response in seedlings and pinosylvin formation in the heartwood.

Twenty independent, petal-specific chalcone synthase (CHS) cDNA clones have been isolated from Petunia hybrida variety Violet 30 (V30). Sequence analysis shows that the largest of these clones contains the entire coding sequence. Using this clone in Southern blot analysis reveals the presence of multiple CHS gene copies in the genome of Petunia hybrida V30. Hybridization and sequence analysis of the CHS cDNA clones shows that they are all copied from a single mRNA species. This indicates the presence of only one transcriptionally active CHS gene in petals. Finally we report the identification, cloning and partial characterization of this gene.

With the help of a cDNA probe for a chalcone synthase gene of Petroselinum a cDNA clone for a chalcone synthase gene of Petunia hybrida could be identified. The homologous cDNA allowed the cloning of two genomic EcoRI fragments from Petunia hybrida containing complete chalcone synthase genes. It could be demonstrated that the genes on the two fragments are different and are not allelic but members of a gene family. The two genes are found in a variety of different Petunia lines including in the two conditional mutants affected in chalcone synthase expression in floral buds, White Joy and Red Star. The structure of the two chs genes from Petunia is compared to the chs gene from Antirrhinum majus.

White flowers of the Petunia hybrida line W43 accumulate glucosides of 4-coumaric acid and caffeic acid and are able to synthesize anthocyanins from exogeneously supplied naringenin, suggesting that W43 is blocked in a biosynthetic step preceding the formation of naringenin. The cultivar Red Star contains a similar mutation as W43; the genetic background of this cultivar, however, allows the production of considerable amounts of anthocyanins in certain areas of the flower. When grown at reduced light, flowers of Red Star are uniformly coloured, whereas under an enhanced light regime the flowers exhibit alternating white and coloured areas. In white sectors of flowers with a colour pattern virtually no chalcone synthase (CHS) enzyme activity could be demonstrated. The enzymes chalcone isomerase (CHI), UDPG: flavonoid-3-0-glucosyltransferase (3GT) and SAM: anthocyanin methyltransferase (OMT) are present, although at a more or less reduced level. From Western blotting and in vitro translation experiments we infer that the absence of CHS enzyme activity in the white sectors of the cultivar Red Star is due to the absence of translationally active CHS mRNA. The potential use of the mutants for genetic engineering in plants is emphasized.

The DNA sequence IS1, which is 800 pairs long, has been shown to integrate into various bacterial and phage operons. The presence of this DNA sequence in the gal operon of E. coli K12 leads to an 30-2000 fold increase in deletion formation in the gal region as compared to wildtype. This high frequency of deletion formation is specific for IS1 and is independent of the cellular recA function. While the frequency of reversion of gal::IS1 mutations, which also is independent of recA, is not affected by the growth temperature of the cells, the formation of deletions in the gal::IS1 system is strongly dependent on the temperature of growth. Mapping experiments showed that one endpoint of the deletions in most cases is at the site of the IS1 mutation and the second endpoint seems to be at various but preferred sites. The formation of the different classes of delections observed is affected differently by the growth temperature of the cells. A model to account for these results is presented.

Genetic analysis of the constitutive revertants of the IS2 mutation 308 located in the control region of the gal operon on the bacterial chromosome suggests that the constitutive expression of the gal genes might be due to inversion of IS2.