Exploiting plant metabolism for the phytoremediation of persistent herbicides.

Weed control by herbicides has helped us to create the green revolution and to provide food for at least the majority of human beings living today. However, some herbicides remain in the environment and pose an ecological problem. The present review describes the properties and fate of four representative herbicides known to be presistent in ecosystems. Metabolic networks are depiced and it is concluded that removal of these comopounds by the ecologically friendly technique of phytoremediation is possible. The largest problem is seen in the uptake of the compounds into suitable plants and the time needed for such an approach

Electrochemically driven respiration in mitochondria and Paracoccus denitrificans The coupling of the electrochemistry of horse heart cytochrome c with respiration in mitochondria and a model thereof, Paracoccus denitrificans

AbstractBy exploiting the rapid, direct electrochemistry of horse heart cytochomre c at a modified gold electrode it has been possible to couple the electrode reaction with respiration in rat liver mitochondria and in photoplasts of Paracoccus denitrificans, but not in protoplasts from E. coli. Oxidation of endogenous and exogenous sources of reducing equivalents via cytochrome c is also observed

Global expression profiling of the response of Arabidopsis thaliana to methanol stimulation

In order to obtain information about the metabolism of methanol in plants, gene expression in response to methanol stimulation was analysed in leaves of Arabidopsis thaliana through the use of a 26,090 element oligonucleotide microarray. Following confirmation of data and the application of selection criteria, a total of 484 (1.9%) transcripts were shown to be regulated in response to a 10% methanol application. Samples were taken at 1, 24 and 72 h. Of the total identified transcripts, only 20 were shared between all three time points of which only two were down-regulated. Based on functional category analysis of these genes, at 1 h, the largest categories were metabolism, cell communication/signal transduction processes, defence genes associated with transcription and aspects of RNA processing; a few related to cell division and growth; but none were associated with photosynthesis. At 24 and 72 h, the number and overall proportion of regulated transcripts associated with metabolism increased further. Direct measurement of anthocyanin and flavonoid content confirmed that methanol-regulated transcripts corresponded to flavonoid pathways. Within the functional class metabolism, genes encoding detoxification proteins represented by far the most strongly regulated group. These included, cytochrome P450's, glucosyl transferases and members of the ABC transporter family. It is concluded that exposure to methanol affects the expression of hundreds of genes and that multiple detoxification and signalling pathways are activated

The assessment of enriched apoplastic extracts using proteomic approaches

In plant tissues the extracellular environment or apoplast, incorporating the cell wall, is a highly dynamic compartment with a role in many important plant processes including defence, development, signalling and assimilate partitioning. Soluble apoplast proteins from Arabidopsis thaliana, Triticum aestivum and Oryza sativa were separated by two-dimensional electrophoresis. The molecular weights and isoelectric points for the dominant proteins were established prior to excision, sequencing and identification by matrix-assisted laser-desorption ionisation time of flight mass spectrometry (MALDI - TOF MS). From the selected spots, 23 proteins from O. sativa and 25 proteins from A. thaliana were sequenced, of which nine identifications were made in O. sativa (39%) and 14 in A. thaliana (56%). This analysis revealed that: (i) patterns of proteins revealed by two-dimensional electrophoresis were different for each species indicating that speciation could occur at the level of the apoplast, (ii) of the proteins characterised many belonged to diverse families reflecting the multiple functions of the apoplast and (iii), a large number of the apoplast proteins could not be identified indicating that the majority of extracellular proteins are yet to be assigned. The principal proteins identified in the aqueous matrix of the apoplast were involved in defence, i.e. germin-like proteins or glucanases, and cell expansion, i.e. β-D-glucan glucohydrolases. This study has demonstrated that proteomic analysis can be used to resolve the apoplastic protein complement and to identify adaptive changes induced by environmental effectors