Tobacco plants, transgenic, containing

Fig. 1. CAT activities in seeds of transgenic tobacco plants containing hs promoter-CAT constructs. A, Schematic structure of chimaeric genes introduced into tobacco. Details of the construction are described by Schoffl et al. (1989,1991). HSE sequences with the consensus C-GAA-TTC-G are symbolised by boxes the synthetic HSE2 is represented by two overlapping soybean HSEs. The CaMV promoter is a truncated silent version of the 35S promoter, providing only the TATA box and the transcription start site. B, CAT assays were performed as described by Schoffl et al. (1989), using 50 pg protein from seed extracts and 10 jig from leaf extracts. Dry seeds (ds) without imbibition and 20 h imbibed seeds (is), derived from the same plant, were used. Heat treatment (hs) was carried out for 2h at 40 °C prior to protein extraction. Control extracts (c) were prepared from leaves incubated at 25 °C. cm, WC-chloramphenicol acm, acetylated form of cm.

Transgenic plants containing a nitrilase specific for the herbicide bromoxynil (= 3,5-dibromo-4-hydroxybenzonitrile)have also been developed [93] the Cal-gene company transformed tobacco plants with the bacterial Klebsiella ozaenae gene encoding nitrilase [94] that detoxifies the herbicide by hydrolysis (conversion of bromoxynil to 3,5-dibromo-4-hydroxybenzoic acid), resulting in the establishment of the herbicide-resistant transgenic plants. 

All the treated and untreated transgenic tobacco plant samples were ground and sieved to 40 mesh prior to the Elcd activity assay. Elcd was extracted from the treated and untreated samples as described by Ziegel-hoffer et al. (15). The total protein of each of the extracts was measured by the Bradford (16) method using bovine serum albumin as a standard. Subsequently the appropriate amount of extract containing the same amount of total protein was subjected to the activity assay. 

The overexpression of both trl and h6h from H. niger in N. tabacum plants have been reported [160]. Here, transgenic and control tobacco plants were fed with the tropane intermediate tropinone. Thus, tropine, the TRI-reaction product, was detected only in leaves of transgenic plants, with no correlation with trl transcript level and tropine amounts. Surprisingly, transgenic tobacco plants contained 3 to 13-fold more nicotine than wild type plants. Also, the presence of considerable amounts of nornicotine, myosmine, anabasine and anatabine contrasted with low levels in wild-type plants, indicating that the overexpression of trl and h6h perturb the normal nicotine biosynthesis when these new genes taken from a different metabolic pathway are introduced in tobacco [160]. 

Studies have demonstrated that 1 plays a vital defensive role in plants. It has been shown that 1 possesses modest in vitro antimicrobial properties [2,7]. In addition, several oligomeric metabolites of 1 are known to exhibit greater antimicrobial activity [8]. Further evidence for the important defensive role of 1 in plants comes from studies in which transgenic barley, wheat, and tobacco plants containing a stilbene synthase gene exhibit enhanced resistance to fungal infection [9,10],... 

Since the first purification of TDC by Noe et al. (177), this protein has been extensively characterized (178-180). TDC is a cytosolic enzyme (35,39,181-183) and consists of two identical subunits (molecular weights of 54 kDa). It showed Michaelis-Menten kinetics ( , 75 /iM) besides tryptophan, it also accepts 5-hydroxy-, 5-fluoro-, 4-fluoro-, and 5-methyltryptophan as substrates. o-Tryptophan acts as a noncompetitive inhibitor, tryptamine as a competitive inhibitor ( 310 /iM) (177). Pen-nings et al. (179) reported that TDC contains two molecules of pyrroloqui-nolinequinone (PQQ) and two molecules of pyridoxal phosphate. Phenylalanine, tyrosine, and l-DOPA are not accepted as substrates in vitro, but in transgenic tobacco plants carrying the Tdc gene, increased tyramine levels were found (184,185). 

Hallard et al. (208) used SSS isolated from a transgenic tobacco cell line containing the Str gene for an assay of secologanin in plant material. Incubation with the crude enzyme, the plant extract, and tryptamine results... 

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