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    Study Reminders

    So, just to brush up Elicitors induced effects in plant cells include effect on calcium metabolismwhich means,because calcium is used as a second messenger and can play a role in transcriptionof certain proteins which may involve their participation in the secondary metabolism.Sotherefore, calcium metabolism can indirectly affect the secondary metabolite biosynthesis. Now, there are reports where there are setreceptors in the plasma membrane of plant cells, where these elicitors bind to. Oncethey bind there is a signal cascade mechanism which can lead to cyclic AMP formation andcyclic AMP bust leads to further calciumion concentration increase in the cytoplasm.Which then binds to proteins thereby thengetting into theor affecting the transcription ofcertain proteins responsible for secondary metabolism. So, massive variations in membraneintegrities might happen, because of elicitor's protein and phosphate metabolism might happenthen ethylene. So, when I say protein or phosphate protein you can directly make out .And even with ions because they are the channels of the permeability of the membrane may getdisrupted, it because of which the electrochemical gradient and can get disrupted. And becauseof the change in the ionic concentration may be the ph can lead to further enhancementin the secondary metabolism or direct release of reactive oxygen species and differentialgene expression. Where Gene expression response to signalsor triggers. So now, consequently forming enzymes concerned in the synthesis of polysaccharideswhich means plant cell wall and enzymes or hydroxy proline rich gluco proteins in thecell walls via induction of proline hydroxylase. So, these are some examples by which differenttypes of elicitors have been found to play a role and induce secondary metabolism .Then polyphenolics which can deposit in cell walls may get altered, then chitinases theseare certainenzyme or PR proteins. If you remember when we had studied it might get altered whichplay a role in secondary metabolism of specific proteins against pathogenic infection, thisis what is PR proteins phytoalexins . Now mechanism of action for the removal ofregulatory repressor genetic manipulation of the enzyme itself, which means that theexpression level can get changed which may be involved in biosynthetic pathways. As metabolicinduces for increase secondary metabolism . Then they can provide stimulus which isthe basis for exploiting the biotechnological potential of these plant cells . Then whenwe say stimulus, stimulus means in the form of over expression of the genes or the encryptedgenes , because of the repressors they may get induced so these are the different ways.So, what are the different these are just example enzymes which get altered by the calciumion concentration in the cell and NAD kinase then NAD oxidoreductase protein kinase. Theprotein which I was talking about where the calcium gets binds, these are generally kinases. Then calcium transport atpases, atpases also get affected because of which the electrochemicalgradients will get affected , then the membranes phospholipases.So, evidence of specific high affinity elicitor binding side, as I said in plasma membraneis available . Innovation of the plasma membrane ATpase that affects the proton electrochemicalgradient across the membrane. Therefore, the signal transduction chain between the elicitorreceptor complexes causes the gene activation process; one of the ways was your calciumcyclic AMP pathway. The signals are either transported locally by diffusion through intracellularor extracellular fluids, infection sides or they can be systematically transferred throughyour xylem elements. Which you remember we were talking about whenwe were discussing secondary metabolism in plants, that salicylic acid ethylene or jasmonicacid were formednear the point of infection and then the signals were sent through xylemto other parts of the plant . So, what is important when we are optimisingelicitors or when we need to optimise what kind of a elicitors what concentration elicitorsspecificity. If elicitors is working well or leading to maximum in enhancement in theparticular species there is no guarantee that it will work well with all the other species.So, there is elicitors specificity involved, elicitor concentration is one of the factorswhich has to be optimised. Duration of elicitor contact is crucial because these being elicitorsthey are affecting the cell viability. So, it has to be taken into account the exposuretime, maybe if you expose it for a longer duration it may affect the cell viabilityand growth of the culture intern leading to lesser productivity. Even if as I was discussingin the earlier classes the ultimate aim is to maximize productivity, then growth stageof the culture at what stage. So, this indirectly involves the time of addition of a elicitor.So, elicitation of cell suspension culture can result in the following things, differentproducts may show high levels of accumulation at different times. If there are more thanone product forming it is not necessary that all the products will get induced at the sametime. So, new product accumulation which might happenas I said I give you an example of cyclotides, some of the novel cyclotides came up in thein vitro cultures could be because of the stress under the in vitro conditions. Becauseyou are not you are growing them in a defined media under controlled conditions which couldhave been a stress to the plant cells, leading to induction of certain genes or expressionof certain genes which were lying encrypted under normal conditions. Then excretion orleakage of the product due to cell breakdown, it is not recommended that the elicitor shouldbe used for product secretion you have set strategies what was that which we studiedin the last class. If you want the product to be out.cell permeability enhancers Cell permeability enhancer's elicitors maylead to break down, but then that leads to compromise in the biosynthetic potential ofthe cell, the growth rate will be compromise or the viability of the cell .Now, what are the different types of elicitors one which are originated outside the cell,I will which induce immediate reactions and these endogenous elicitors which are formedby secondary reactions. Which means once the infection has taken place outside then thesubsequent changes or the signal transduction maybe which happens also form the class ofsecondary metabolites. These are called as endogenous elicitors and what will impactthe first the cell would be or exogenously would be exogenous elicitors .Now, even in that there are two classes which I referred one is biotic elicitors and theother is a biotic elicitors depending on their origin . Now biotic elicitors these are directlyreleased by microorganisms and recognised by the plants cells enzyme cell wall fragments,then formed by the action of microorganisms on the plant cells like for example, fragmentsof pectin's can be . Then formed by the action of plant and enzymeson microbial cell walls then you would end up if it is a fungus, then you can see chitonthen or carbohydrates cell wall components. Then compounds endogenous and constitutivein nature formed or released by the plant cell in response to various stimuli. Abioticelicitors they can be of physical or chemical in nature they influence endogenously formedbiotic elicitors. So, the a biotic elicitors like physical factorsu v light can be one, then yourfreeze suddenly you freeze and thaw freeze thaw cycle canbe a stress. Then a medium components like agarose agri jell like for example, I toldyou once you bring in the culture under in vitro conditions you are growing at in thepresence of such components, which may cause an impact on the secondary metabolism .Now, chemicals which can disrupt membrane, for example you are detergents fungi sideherbicides anything which can cause stress. But it is of synthetic nature than that formsa biotic elicitors. Now, biotic and Abiotic elicitor they differin their dose effect relationship what does that mean ?Which means what what is needed that is the reason why concentration optimisationis necessary, at what concentration it is you cannot generalize every biotic or a bioticelicitor. Because they are specific they are concentrationdependent exposure time dependent, so optimisation is necessary . Not all enzymes as I said earlierwill get affected by a particular elicitor, a particular elicitor might be affecting oneparticular enzymeanother elecitor might affect some other enzyme in the pathway . Then concentrationof the elicitor used is critical for maximum effect on the cultures, product accumulationgenerally what is observed is as you would increase the product you will would increase,but beyond a certain concentration it will decrease why?saturation saturation . Saturation.innovation . Right because it is balancing between theyield enhancement and the toxic effect on the cell .So, what are biotic elicitors which originate in the invading organism in which case theyare referred as exogenous, endogenous elicitors which are biotech in nature can be of plantorigin and are generated by interaction between the microorganism . Which means the pathogenand the plant which may be plant components then biotic elicitors. For example, polysaccharidesglycoprotein's lipids lipopolysaccharides oligosaccharides any active component whichis coming from of biological origin. If endogenous is coming after the attack from the plantcell itself or if coming from the pathogen it is exogenous, but a biotic elicitor .What are a biotic elicitors as we said diverse collection of molecules they are not derivedfrom natural sources, such as tissues of pathogen these are from natural sources of biologicalorigin . But a biotic for examples also heavy metals these are very frequently used in literatureas Abiotic elicitors molecules involved in signal transduction pathway. If syntheticallyyou exogenously add them they are considered as Abiotic elicitors. For example, salicylicacid jasmonic acid if you add them exogenously .Then detergents factors that can cause stress physical factors repeated freezing thawingcycles wounding creating wounds, then exposure to UV light which can be a stress temperatureshock which is heat shock .