An approach of plant genetic engineering for pentachlorophenol remediation

Aromatic hydrocarbons (AHs) constitute a class of highly toxic compounds released in the environment due to industrial and agricultural activities. They accumulate in the environmental compartments, including soil, and propagate into trophic levels of the food chain till humans. At this level, they can be toxic, mutagenic, carcinogenic and teratogenic. Several strategies based on physical and chemical methods or involving biological agents are applied to remediate polluted environments. Living organisms, through their enzymes may degrade organic molecules into harmless inorganic end-products. Bioremediation, as a spontaneous or controlled strategy, is usually considered a low-impact and sustainable methodology that uses several agents like plants and microorganisms. Recently we isolated a number of indigenous fungal species from soil contaminated with pentachlorophenol (PCP) and we introduced them in a collection and catalogued according to their ISSR profile. Among all, a strain of Byssochlamis nivea showed a conspicuous degrading activity on PCP when added to the culture medium. The aim of this project was to identify genes and pathways involved in PCP degrading processes in B. nivea to exploit them for engineering bioremediation tools. However, DNA and RNA sequences at genomic level have not been provided so far in B. nivea thus tremendously limiting biotechnological approaches in this species. Therefore we produced a normalized 3'-fragment cDNA library from mycelia grown in different conditions of media composition, pH, temperature, light intensity and PCP supplementation. This library has been sequenced by 454 FLX technology and the assembling procedure produced 34880 contigs and 88400 singletons. B. nivea mRNA sequences putatively involved in PCP degradation have been mapped by similarity according to MetaCyc PCP degradation pathway (http://biocyc.org/metacyc/index.shtml). Changes in the expression of these mRNAs are being profiled by transcriptomic approach following PCP supplementation in the culture media of B. nivea. These genes are being cloned for their expression in the yeast Yarrowia lipolytica and tobacco plants. Further functional characterization of candidate genes will provide additional insights on molecular mechanisms and processes involved in detoxifying hazardous contaminants. Also, characterization of engineered yeasts and plants is expected to provide additional cues in implementing new systems for remediation, in confined environment, of contaminated soil and waters.