Anthranilate synthase and chorismate mutase activities in transgenic tobacco plants overexpressing tryptophan decarboxylase fromCatharanthus roseus

TransgenicNicotiana tabacum L. Petit Havana SR1 F₁-plants expressing tryptophan decarboxylase cDNA (tdc) fromCatharanthus roseus (L.) G. Don under the control of the CaMV 35S promoter and terminator exhibited tryptophan decarboxylase (TDC) enzyme activity and accumulated tryptamine. The plants with the highest TDC activity contained 19 pkat per mg of protein. The influence of transgenic expression oftdc on the activities of anthranilate synthase (AS) and chorismate mutase (CM) were examined in 10 transgenic tobacco plants. The specific activities of these two chorismate-utilizing enzymes were not significantly affected by expression oftdc, despite their important functions as branch point enzymes in the shikimate pathway. The results indicate that the normal route of tryptophan biosynthesis in plants is sufficient to supply a considerable amount of this essential amino acid for the biosynthesis of secondary metabolites. Despite their increased tryptamine content, the growth and development of the transgenic tobacco plants expressingtdc appeared normal.     

394delTT: a Nordic cystic fibrosis mutation

In a systematic screening for mutations in the gene encoding the cystic fibrosis transmembrane regulator among Danish cystic fibrosis (CF) patients, we identified a mutation in exon 3 (394delTT); this mutation was found to be relatively common in Denmark. We therefore screened for 394delTT in Sweden and Norway, where it turned out to be the second most frequent mutation, accounting for 4% of all CF mutations. It also occurs with a high frequency in Finland, but has not been found in larger surveys of mutations in the CFTR gene. Thus, 394delTT seems to be a specific Nordic CF mutation.     

Chromium-induced inhibition of ethylene evolution in bean (Phaseolus vulgaris) leaves

The influence of chromium concentration on ethylene production in bean plants ( Phaseolus vulgaris L. cv. Contender) was investigated. A Cr ion-induced inhibition of ethylene synthesis from endogenous 1-aminocyclopropane-1-carboxylic acid (ACC) was observed within both leaf discs floated on 2 m M CrO²⁻₄ or Cr³⁺ and leaf discs from plants cultured in nutrient solutions containing 10, 20 or 40 μ M CrO²⁻₄. However, Cr ions supplied either to plants with the nutrient solution or to discs with the incubation medium rather increased the conversion of exogenous ACC to ethylene. Primary leaves of plants exposed to CrO²⁻₄-containing nutrient solutions showed a statistically insignificant decrease of ACC-synthase activity. In the trifoliolate leaves of plants exposed to 10 μ M CrO²⁻₄, in which a significant decrease of ethylene production from endogenous ACC was observed, a substantial increase of ACC synthase was found. These results indicate that Cr ion-induced inhibition of ethylene production is not due to a breakdown of membrane integrity, which is necessary for ethylene forming enzyme activity, but caused by metabolic alterations leading to decreased ACC availability. Chromium ions may act by inhibiting ACC synthase activity or by diverting a metabolic step prior to the ACC synthase catalyzed reaction.     

Plant regeneration through culture of isolated microspores of Triticum aestivum L.

Wheat microspores mechanically isolated from the anthers before culture and isolated from the anthers during the hole culture period in a chemically defined medium resulted in proembryos, embryos and finally plants. Of the four genotypes included, all responded with proembryos, and the two spring wheats Ciano and Walter gave rise to macroscopic embryos and plants. The frequency of embryo regeneration and the frequency of albino plants in both Ciano and Walter was in accordance with previously obtained results with anther culture derived material.Abbreviations 2,4-d 2,4-dichlorophenoxy acetic acid - NAA 1-naphthaleneacetic acid     

The 28 kDa apoprotein of CP 26 in PS II binds copper

Photosystem II (PS II) particles isolated from spinach in the presence of 10 M CuSO₄ contained 1.2 copper/300 Chl that was resistant to EDTA. When CuSO₄ was not added during the isolation, PS II particles contained variable amounts of copper resistant to EDTA (0.1–1.1 copper/300 Chl). No correlation was found between copper content and oxygen evolving capacity of the PS II particles. To identify the copper binding protein, we developed a fractionation procedure which included solubilisation of PS II particles followed by precipitation with polyethylene glycol. A 22-fold purification of copper with respect to protein was achieved for a 28 kDa protein. Partial amino acid sequence of a 13 kDa fragment, obtained after V8 (endo Glu-C) protease treatment, showed identity with CP 26 over a 14 amino acid stretch. EPR measurements on the purified protein suggest oxygen and/or nitrogen as ligands for copper but tend to exclude sulfur. We conclude that the 28 kDa apoprotein of CP 26 from spinach binds one copper per molecule of CP 26. A possible function for this copper protein in the xanthophyll cycle is discussed.Abbreviations CP 26 and CP 29 chlorophyll a/b protein complex 26 and 29 - LHC II light-harvesting chlorophyll a/b protein complex of Photosystem II - SB14 sulfobetaine 14 A preliminary report of these results was presented at the IX Int. Congress on Photosynthesis, Nagoya, Japan, 1992.     

Widespread formation of intracellular calcium carbonates by the bloom-forming cyanobacterium Microcystis

The formation of intracellular amorphous calcium carbonates (iACC) has been recently observed in a few cultured strains of Microcystis, a potentially toxic bloom-forming cyanobacterium found worldwide in freshwater ecosystems. If iACC-forming Microcystis are abundant within blooms, they may represent a significant amount of particulate Ca. Here, we investigate the significance of iACC biomineralization by Microcystis. First, the presence of iACC-forming Microcystis cells has been detected in several eutrophic lakes, indicating that this phenomenon occurs under environmental conditions. Second, some genotypic (presence/absence of ccyA, a marker gene of iACC biomineralization) and phenotypic (presence/absence of iACC) diversity have been detected within a collection of strains isolated from one single lake. This illustrates that this trait is frequent but also variable within Microcystis even at a single locality. Finally, one-third of publicly available genomes of Microcystis were shown to contain the ccyA gene, revealing a wide geographic and phylogenetic distribution within the genus. Overall, the present work shows that the formation of iACC by Microcystis is common under environmental conditions. While its biological function remains undetermined, this process should be further considered regarding the biology of Microcystis and implications on the Ca geochemical cycle in freshwater environments.