natural-products-in-plant-pest-management

Biotechnology and Natural Product Synthesis 269example of this approach is reported by McDaniel et al. (1999) who engineerederythromycin polyketide synthase to produce a library of over 50macrolid antibiotics. Kantola et al. (2003) provided an analysis of availableliterature on this subject giving details of the gene clusters involved. Hopwoodet al. (1985) was the first group to produce ‘hybrid’ antibiotics by transferringgenes encoding enzymes making a set of antibiotics in one strain toanother. This results in new antibiotics depending on the substrate specificityof the enzymes. Thus the possibility of finding more efficient antibiotics ismade possible.Metabolic engineering or combinatorial synthesis of traits frombacteria to plants has also been successful. For example, a bacterial geneencoding p-hydroxycinnamoyl-CoA hydratase/lyase (HCHL) has beenexpressed in Beta vulgaris. One line was able to accumulate the glucoseester of p-hydroxybenzoic acid (pHBA) at a rate of 14% of dry weight(Rahman et al., 2009).Combinations of different approaches are of course possible and sometrials have already given positive results. The effect of combining metabolicengineering with providing elicitors in the culture medium has been testedby Zhang et al. (2009) in flavonoid production by hairy root cultures of Glycyrrhizauralensis. In metabolic engineering, overexpression of chalcone isomerasewas achieved by Agrobacterium-mediated transformation with a 150%increase of total flavonoid over the wild type. When PEG8000 and yeastextract was added to the medium, the engineered line produced over 300%total flavonoids.Plant tissue and cell culture in natural productsMany higher plants produce economically important organic compoundssuch as oils, resins, tannins, natural rubber, gums, waxes, dyes, flavours andfragrances, pharmaceuticals, and pesticides. Plants have been identified sinceancient times as a source of remedies for ailments. Medicinal plants, eventoday, are given the highest importance in the pharmaceutical industry,despite the fact that some of these chemicals, which were first identified asbotanicals, are synthesized chemically. It is a general rule in nature that if onehas continued enthusiasm, patience and the right approach, one shall encountera better performer of the function of interest. Natural product formationis no exception. Screening of natural plant populations has taken placethroughout civilization and will continue. This is now happening in a morerigorous manner at the level of genetic diversity and identity with the aid ofmolecular biology and biotechnology tools. On the other hand, it is also possibleto use the biotechnological tools for the generation of new varieties withmore desirable traits, as discussed in the above section with regard to microorganisms.Once a better performer is identified, the next concern would behow to maintain the genetic constitution so that it would be used for a longperiod without genetic variation. Tissue culture is the first option availablefor the clonal propagation of plants within a short period of time in a small