Elicitor biotic

Another strategy for the improvement of secondary metabolites production is the addition of elicitors (biotic or abiotic) [68]. 

Other methods used to increase secondary product accumulation are elicitation, permeabilisation, product removal, immobilisation and differentiation. Elicitation is the triggering of plant defence mechanisms by the addition of abiotic and biotic elicitors. Elicitor refers to chemicals which can trigger physiologi-... 

Borie B, Jeandet P, Parize A, Bessis R, Adrian M. 2004. Resveratrol and stylbene synthase mRNA production in grapevine leaves treated with biotic and abiotic phytoalexin elicitors. Am J Enol Vitic 55 160-164. 

To increase production and facilitate isolation, plant cells have been immobilised on various matrices such as polyurethane foam and calcium alginate gel beads,24 while elicitation (i.e. the induction of a defence response) is generally critical for the production of secondary metabolites. The rationale for the use of elicitors is that plants produce secondary metabolites as part of a defence response to stress, either biotic (pathogen infection) or abiotic (ultraviolet, toxic heavy metals and rare earth ions). Jasmonic acid plays a crucial role in plant stress responses and, along with fungal polysaccharides and heavy metals, is the most widely employed elicitor in plant tissue cultures.30... 

With a few exceptions, the characteristic problem of cultivation of plant explants in in vitro cultures is a low production of secondary metabolites by these cultures. One of the methods which can achieve an increase in the production of natural substances in in vitro cultures, is elicitation of cell cultures with biotic elicitors. For example, hairy root cultures of Cassia obtusifolia L. clones transformed with Agrobacterium rhizogenes strain 9402 were established to investigate anthraquinone production. It was found that changes of the elements in the culture medium and the addition of rare earth element Eu3+ can greatly influence the contents of free anthraquinones in the hairy root [320],... 

On the other hand, and since alkaloids constitute a defense against certain environmental stresses, it is not surprising that the TIA pathway shows induction by several biotic and abiotic stress factors [6, 133-137], Among those, the induction by fungal elicitors has been particularly well characterized, together with the regulation by the plant stress hormone methyljasmonate [5, 9]. 

The use of elicitors can significantly enhance the production of metabolites. The elicitors are divided mainly in two groups. The biotic elicitors which are compounds of biological origin (e.g. fungal spores, fungal cell wall fractions, cellulase, chitosane) and the abiotic elicitors which include metal ions, high salt concentrations, UV radiations, sonication. Treatment of Hyoscyamus muticus hairy roots with 50-500 jig/ml of chitosane resulted in a 5-fold increase in the accumulation of hyoscyamine [84]. Similar results were obtained by Halperin and Flores [85] who obtained, with hairy roots of the same species, hyoscyamine up to 6-fold when elicited with mannitol. 

Elicitors are probably the best-studied exogenous signals in plants. They are connected with microbial infections and induce plant defense responses. Among others, the production of certain secondary metabolites (phytoalexins) is induced by biotic or abiotic elicitors (e.g., see reviews in refs. 326-328). 

The results for alkaloid production after elicitation with a biotic elicitor (e.g., Pythium or Phytophthora preparations) differed in the various studies published. Tryptamine levels were, if determined, found to be increased. The production of ajmalicine, serpentine, and catharanthine was also reported to be increased (329,330,333-337). Nef et al. (334) found that catharanthine and ajmalicine were excreted into the medium, whereas serpentine was mainly found in the cells. 

If the biosynthetic pathway it is known, the addition of precursors may stimulate the product formation. Also, the addition of biotic and abiotic elicitors is a strategy for the enhancement of secondaiy metabolites production. 

Advanced technology of a benchtop bioreactor has facilitated continuous extraction of secondary metabolites, which is designed for Catharanthus roseus L. (G.) and Santalum album in plant cell suspension cultures. C. roseus cells were exposed by biotic elicitors (Aspergillus niger, crude chitin), abiotic elicitors (mannitol, MJ), and induced the alkaloid production (Valluri 2009). 

QAs production can be stimulated by applying abiotic, for example, CuCl2, or biotic elicitors, so-called phytoalexins, prepared, for example, from cells of fungal mycelium [37]. 

Various biotic and abiotic elicitors have been used to increase colchicine production. Application of methyl jasmonate as a biotic elicitor in the media showed increase in growth of the root cultures of Gloriosa superba. Higher concentration of methyl jasmonate decreased growth but enhanced intracellular colchicine content of the root cultures. However, such treatments with methyl jasmonate did not release colchicine into the medium [22],... 

Different strategies, using in vitro systems, have been studied extensively with the objective of improving the production of colchicine, like media manipulation establishment of cell culture, organ culture, and root culture of colchicine-producing plants elicitation with biotic and abiotic elicitors etc. Instead of these progresses, production of colchicine at commercial scale is yet not achieved. 

The term elicitor refers to chemicals from various sources, biotic or abiotic, as well as physical factors, that can trigger a response in living organisms resulting in a high accumulation of secondary metabolites. Therefore, elicitors are usefiil tools for improving the production of plant valuable compounds ([36] and references therein). The effectiveness of elicitation as a tool to enhance the production of secondary metabolites depends on a complex interaction between the elicitor and the plant cell. There is evidence that the same elicitor can stimulate secondary metabolism in different cell cultures and that certain plant cultures are responsive to diverse elicitors. Treatment of a particular plant cell culture with different elicitors will result in the accumulation of a particular class of compounds, since these are specific of each plant culture. Although the class of metabolite depends on the plant species, the kinetics of induction or accumulation levels can vary with different elicitors. 

As has been described previously, V. vinifera cell cultures have been used to the production of trans-R [22, 25]. The main advantage of these cultures is that genetic modification of cells is not necessary because grapevine cells produce trans-R constitutively, or in response to stress, so grapevine cell cultures can be directly exploited. Therefore, the use of biotic or abiotic elicitors could be considered one of the most effective strategies to increase the productivity of this compound. 

The Use of Biotic Elicitors Enhances frans-Resveratrol and Stilbene-Related Production... 

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