Plant Immune System

hello aunt good afternoon friends welcome to CEC at ESET live lecture dear friends have you ever heard about that plants get affected and when they are infected look at the disease’s how they respond to dear friends today we are going to discuss on basics of plants immune system for this we have with us in our studios professor dr. Ashish Ananda he is from JNU from the School of Life Sciences and under his able guidance today we are basically going to discuss about and how do plants respond to the immune system if they are infected what does they do how they protect themselves so first of all I would like to welcome our guest dr Ashish nan theme hello sir welcome to the Edit lecture and most of us have would have never ever heard about that plans also get infected and they too have a good immune system with the help of which they fight with the disease’s what basically this immune system is and how plants was basically respond to we basically want to know through you okay thank you very much I hope I will able to rework whatever I want to and I should we understand able to basically anybody did biology up to class 12 and with basic instinct towards learning biology should be able to follow this lecture so let me begin with okay yes so the title of my talk today I have kept as basics of plant immune system so because when you speak about immune system immunity the first thing which strikes in our mind is like antigen antibody having a circulatory system like blood but unfortunately plant don’t have a circulatory system but they have a very strong immune system so I will try to speak today how plants get infected and what plants do when they are under infection pathogens can cause serious disease and to an estimate that up to about 30% of yield loss takes place worldwide due to different kinds of diseases so this is a field of your eyes where it part you can see it’s turning brown and this is due to the infection on rice plants so this infection can takes place due to multiple different kind of pathogens here a few examples are there you can see in the left side most it’s a corn disease is disease and corn due to a fungus or Fusarium and next we say disease caused by any method called root-knot nematode and then it’s a bacterial disease on rice and at the last right mode and you can see a viral disease on soybean so basically you can see that large varieties of crop plants can be infected by large number of kinds of microbial pathogens now in spite of having passed a number of pathogens and mostly of majority of them reside on soil if you on an average if you take a gram of soil you can get as many as 100 crores of bacteria in itself so that tells you plants actually live in in an ecosystem where they have to deal with millions of bacteria at any given time of point not only bacteria bacteria fungus virus everything in spite of that you will say the earth surrounding you is very green and that itself suggests that plants have very strong immune response and in fact in plant disease is an exception and Hill deenis is community common so these are basic steps or plant pathogen interaction and immune response so pathogen would infect and once it is infected the plant would recognize it so the recognition comes after infection and there is a level of resistance higher plants develop resistance and try to read or suppress the growth of the pathogens and once they are successful in suppressing growth of the resident it develops a sort of memory

infection memory and through this infection memory once plant is infected they learn how to tackle this infection better in the next time so if the same plant is infected second time pathogen infection or growth of the procedure will be much lower then what happens during first time so this is what is called as systemic occur resistance so if time permits I will speak about systemic or resistance as well so begin with infection there are large varieties of pathogens as I told you earlier can grow on plants and they can be broadly classified into three groups some are called necro drop some are called bio trough the an other circled Hemi bio trough these necro troughs they point they come in close to the plant they try to kill the host so they first kill and once the host cell is killed the nutrients which is there in the cell is used by the pathogen to grow over here disconnect out of in contrast bio trough love to keep the host alive so they will keep the host alive as long as they code and eventually at the end of process of course the host is died so they occur by trough which love to grow on host and Hemi buy a trough is a combination of both like they begin like buy a trough and the continued even growing even after host is dead so they are call him you buy drove so basically if you say there are broadly two classes of strategy by the microbes one group is a buy trough and they live with the host something called as a pretend harmony they’re not actually growing harmoniously but they tried to escape detection by the host and because less damage compared to the negative at the beginning where is the necro tops which are shown in the right side are kind of a smash-and-grab so essentially you can say Wyatt trough it to kill whereas network of kill to eat so this is an example of a by trophic fungus and these by traffic fungus they grow between the cells as it’s shown in the right side and they generate a feeding organ car historian this historia would grow inside the cell and that growth eventually will help to occur nutrition from the plant cell in the left side it is shown a real picture historia is grown in a plant host diesel this is a figure photograph of Arab DOCSIS thaliana many of you who may not know about this plant this is a plant of a mustard family plant and the genome is fully sequenced in fact we the frost plant her genome were sequenced completely and for many scientific reasons this plant is used as a model plant for modern plant physiological or agricultural research so this is the Arab DOCSIS plant and it has very grown on a bacteria which belongs to Jenna’s car Pseudomonas and this is Pseudomonas syringae infected bacteria sylvan was syringe a bacteria infected our abrasax plant and if you look very closely you will find this bacteria grow between the cells you can see here this bigger as our plant cells and the tiny particles feature between the cells are bacteria so bacteria can never enter the plant cell they always remain outside and by remaining outside they modify the host cell in such a way that they release nutrient from the cell to the bacteria outside so I’ll come into that this is another picture her bacteria are trying to enter host throws to matter this is a picture of a root not in a method this methods are like insects as you can see in the inset picture it’s like insect it’s gross three to four millimeter long and sometimes visible by it’s also visible a naked eye but they are the count can cause devastating damage on the plant they colonize in the root zone and infect root and eventually in that process they can kill the entire plant

these are some cross-section of plants which there infect said when I met on you can see this arrow mark cells arrow mark these are the nucleus you can see mega cells found by multiple round of division and there is enhanced cell division and all together makes budging of the growth which you call as not permission this is a picture of a nematode stylet this nematode has a way of feeding from the plant by putting a stylet so it’s a feeding tube this feeding tube is inserted in the host and through this feeding tube it can draw nutrient for consumption by the nematode so this is now coming to bacterial infection this is quite interesting you can see through this these slides like here this bacteria as I told you earlier bacteria can never enter the cell plant bacteria can never enter the cell so they will remain outside and remaining out being staying outside they inject some kind of toxin molecule inside the cell so in case of plant or any other himself the plasma membrane is the major barrier for flow of nutrient so nutrients do not flow spontaneously and there is a a flow is restricted in the plasma membrane so this bacterial pathogens what they do they can really some toxin molecules as you can see in this figure this is drawn here a bacterial pathogen written is supposed to be for bacteria and it also has a stylus hearing like structure but unlike nematode this is not a feeding tube through this tube the bacteria inject toxins inside the cell and that toxins eventually work on disintegrating the plasma membrane so the nutrient from the cell is thrown outside higher bacteria is growing and bacteria can feed on those nutrient so this is the elevated structure of a syringe and maybe if somebody is interested more they can look into literature there are lot good I want ability research available especially on the animal bacteria this mode of infection is conserved both implant and the last type of organism that I will discuss is virus and virus is the only plant pathogen that can enter the cell so many times virus particles are delivered inside the cell or even outside the cell higher virus the genomic component is my either made of DNA or RNA and this DNA or RNA being inside the host cell can modulate host metabolism and in such a way that can favor the multiplication of bacterial DNA so at the end this host cell which is drawn here can support large number of viral DNA and viral proteins and eventually it can spread through the entire plant so this is how the virus infects so eventually what we have learnt now so far is plants are infected by virus plants are infected by bacteria plants are infected by nematode and as well as fungus and they pose serious threat on the survival of the host but now what I will discuss now that how immune system is so strong which can get rid of there was infection and can live happily so we see the second point that I am discussing today is recognition can I have the slides soon please show this light thank you this slides shows that a model system this is true for any kind of pathogen but this drawing shows that the larger green color is the plant cell inside the cell blue color is nucleus and in the nucleus you have genes which code for everything in room difference response plant difference response is mostly restricted at the DNA level so the immune response effect takes place inside the nucleus on the transcription level but the pathogen is I told you earlier

other than viral DNA none of the pathogens enter the cell so they remain outside now you can see that plant cells have large number of receptors on the plasma membrane these receptors are like over here this receptor is drawn here this can recognize certain molecules which are non host molecules like for example I am telling you that some of the proteins carbohydrates even DNA protein of the microbes have some features which are never present in the plant or say larger in karate host so those serve as a signaling molecule and there are two types of signaling molecules one or maybe they are called as a pattern molecules so this can be either microbe associated molecular pattern or pathogen associated molecular pattern there this pattern is not due to a protein per se but a small part of a protein which can fold in a very unique way and that unique fold is not present in the plant or host so it became a source of a pattern so this receptor which is shown here it’s for the bacterial flagellum there’s a very good source of pattern this bacterial flagella has a protein which is made of a puzzle in this fragile in protein some part of it has a very unique feature which is not present in the plant and can be a source of it pattern for the host immune response to be activated similarly the bacterial cell wall for example cell wall also have certain molecules am i know i said carbohydrate composites and molecules which are different from host cell that can be patterned and in edison large number of microbial pathogens also get broken down outside the host cell this broken down component like DNA RNA protein other internal proteins also can be source of pattern so all this pattern can be recognized by the host cell and that recognition will eventually lead to a signal transduction and that signal transduction will reach all the way to the nucleus higher different genes are situated and that will turn on the expression of defense genes in favor of the immune response so now then how pathogens grow so earlier i told you like bacteria for example inject lot of toxin molecules inside so some of this toxin molecules or toxin like molecules are called effector molecules these effector molecules are recruited by the pathogen to suppress immune response and many of them have to grow pathogen and many of these effector molecules are recruited for suppressing immune response so this is a different kind of recognition that takes place inside the host cell so earlier I told you pattern receptors there in the plasma membrane and this set of receptors which are called as effector mediated effector receptor they’re inside the host cell these effectors which are secreted by the microbes inside the host cell are recognized by these receptors and that recognition can lead to very strong and very high level of immune response so this very high level of immune response is called as effector trigger immunity or ETI in short now the special requirement for this ETA to be activated and naturally is that there has to be a system that would recognize inside the host and that effector molecule from the pathogen also so to match with the receptor molecule so this concept is called gene for gene concept where one gene product of the pathogen soon-to-be compatibly matching with one gene product of the planet so this is what is called as a gene for gene interaction

and naturally when this matching takes place as it’s shown in the tabular form in the right side like effector molecule if it gets a matching a recognition molecule also this capital R stands for resistance molecule because when this matching combination takes place then the plant becomes very resistant and if that resistant condition pathogen cannot grow so this is called also resistance genes and when there is a matching combination this effector molecules provide a virulence instead of virulence so they’re also called a virulent factor so in case of gene for interaction there has to be a matching are in here combination so when our AV ER combination matches you get resistance but if they do not then you get disease so either absence of R or absence of AV air will lead to disease so a lot of resistance genes or our genes have been cloned from many plants like Arab dog sees as I showed you into Matt from tomato from paper and the common features for most of the our genes is that all of them look like two receptor so this is a figure from a science paper where it sews the mult of receptor genes which so far has been isolated having a role in resistance and quite interestingly this plants are genes which over here have lot of similarity with mammalian receptor as well as drosophila receptor so in drosophila there is a receptor called Talde receptor so many of the biology students have learnt about signaling pathways mediated by toll or in mammalian system called interleukin receptor and this plant our genes many of them have a commonality with Drosophila tall receptor or mammalian interleukin receptor so they are in short also called as a TIR tall interleukin and are for resistance in the plant so this is which looks like a unified for feature of immune response be it a plant with a fly or large mammals so so far whatever I told you about recognition there are two kinds one is a pattern recognition and one is it affected about a commission and depending on the type of recognition you get two different kinds of immune response or in short they’re called pattern triggered immunity and affected regard immunity so this ETI or affected triggered immunity is much stronger firm than PDI but overall contribution of PT a– is very huge because eta is a case specific where AR area combination is there so if you now compare between this two one i told you as a pattern triggered immunity and another one is effector triggered amenity pattern triggered immunity takes place through a general receptor response is milder and if Hector trigonometrical be et I in the right side instead of a TI is a specific receptor and that gives a very strong immune response and when immune response is milder pathogen can grow so in terms of plant and pathogen interaction this is called a compatible interaction that means pathogen can grow on this host plants in contrast when eta is activated if it total immunity is activated the immune response is so strong that pathogen cannot grow and in that case the plant pathogen becomes an incompatible content interaction so if someone looks into the comparative evolution between pti and EDI it appears that this spam molecules can be a source of immunity and this arrows length and thickness of

the arrows indicate the strong strength of the immunity and this pam molecules can give you immunity to a moderate level and then if there is an RF here combination resistance becomes very high and then eventually the plants makes a new urine antigen and and again maybe after a few hundred million years later that or maybe few million years later the plant would make another different Arjun to combat a a new developed effector molecule so our fear evolution is a dynamic change which takes place in the Eva leaves and constitutive constantly so now I’ll talk I’ll come to immune response like and we’ll discuss about how immune response is activated in the plant and as I told you there is something called local resistance and something is systemic occurred resistance local resistance means if the plant is infected then plant will mount resistance on the same infected tissue and that resistance will suppress the growth of pathogen that is called as local resistance so so mechanism of resistance actually when you talk about well you can broadly classified into two one we call it a structural defense and another one we call as chemical defense this structural defense is by virtue of the plants very strong structural component and all of the biology students know that plant cell differs from animal cells by the presence of a cell wall cell wall is composed of cellulose hemicellulose pectin and a large number of proteins which make together a very tight outer layer that itself becomes a challenge for many pathogens which cannot really do well besides this every cell is own cell wall many of the plants especially like leaf have a additional to tickle layer this cuticle is layer depositions also pose a barrier for the pathogens to come in close proximity to the plant cell and kalos kalos is a modified poly mar of glucose and that can also add an additional layer of security or protection over the cell wall besides this cell wall component which is already there epidermal cuticle which I told you many of the cells are known to have significant the solidification makes plans for a very strong like all the large trees you see they are tree and very strong because of the lignin of some of their cells and that also pose a barrier to the pathogens and another structural difference Costa metal closure this tomato closer like as I showed you earlier that bacteria can enter first a matter Frantz have a mechanism if they can sense that pathogen is their own they tried to close to matter and when the stoma is tightly closed that itself become a resistance for the pathogen to breach the plants protective layers to go inside the cell so other than the structural differences plants also have chemical differences when the plants are infected they can make and sacred large number of chemicals creature antimicrobials there are many plants secondary metabolites actually there’s plants are reaching secondary metabolites and many of the secondary metabolites are antimicrobial and when provisionally infects them plants back in much higher amount like there can be terpenoids like pyrethrin saponin it can be phenolics phenolic SAR the largest number of largest group of components which are anti microbials hydraulic scenes is a type of paranoid colonics alkaloids these are there but quite

interestingly when a plant is infected it makes a large number of proteins that are also antimicrobial so they are called as peptide antibiotics this peptide antibiotics something they code for enzyme like chitin is glucan is and like a defense in so this peptide antibiotics can eventually work on microbes and can kill them so one set of defense comes from the structural component and other set of defense come from the chemical component and interestingly both the structural component and chemical component can be present constitutively in a given plant or can be induced when a plant is under attack constitutive means that is always present like as I told you cell wall component epidermal callosity position they are always there but it enhances further or in a pathogen infected similarly like terpenoids phenolics they are our vessel amount which can provide vessel resistance but when a pathogen is infected plants accumulate in much larger quantity and that larger quantity helps the plants to get rid of those microbes so now will come little bit about regulation of this plant immune response and quite interestingly the immune response of plant is largely regulated at the transcriptional level so the transcriptions means like again this is a thing which most of the biology students know that DNA is the genetic material for most higher organisms and this DNA converts into RNA by a process called transcription and this RNN part of RNA which are called a cell messenger RNA which messenger RNA codes for protein which the process called translation and when a pathogen infect a plant as I told you earlier that receptors ultimately signaling goes inside nucleus and the expression of genes change that which transcription changes translation change and make a set of proteins these proteins in turn can lead to the biosynthesis of structural components by studies of chemical components which I described just a few minutes back this proteins also can modulate translation and these proteins also can modulate transcription of other genes so eventually activation of few receptors molecules by the cell can activate the expression of a large number of genes which all together work in the favor of immune response and a large number of genes transcription gets changed and a good varieties of proteins are really made which are called as PR proteins or pathogenesis related protein so this pure protein I’ll come quite a few times in my talk today because this pure proteins are also an indicator for the biologists like us who work on immune system to determine or to find out how much immune response are activated so this is the sequential event of immune response can I have the slides please slides yeah thanks so this is the sequential events of immune response so it all begins with a receptor activation and this is what I had been talking so far and once receptor is activated it can be both patterned receptor as well as affective receptor so once the receptor is activated plants accumulate large amount of reactive oxygen species and which is very quick response usually it can start as early as five minutes of the pathogen infection and then sometimes plants activates its own cell death that is not always this activation of cell death takes place but special it takes place when gene for gene interaction takes place so it’s a part of the ETI higher cells undergo ourselves program for its own death and

following by this reactive oxygen species accumulation whether there is a hypersensitivity reaction or HR is there or not it leads to transcriptional reprogramming and then expression of pure proteins and small organic molecules like phenolics and flavonoids so will speak these aspects a little bit of each and every aspects what I told you like the first aspect down to immune response is accumulation of reactive oxygen species so we know that oxygen molecule can oxide can oxidize the substrates and modify them chemically but sometimes with oxygen can be superoxide by having extra electrons within them so they are like hydrogen peroxide hydroxyl radical singlet oxygen they are superoxide and their oxidation power is more than molecular oxygen so this is a chart which shows you how and different forms of super oxides are generated it there can be superoxide radical peroxide ion hydrogen peroxide and hydroxyl radical this is a process of superoxide generation is universally there all the time in plants and it’s a part of normal metabolism where oxygens become superoxide and through a set enzymes they convert back into water like something called superoxide dismutase or a Saudi this a Saudi can convert superoxide to hydrogen peroxide and this hydrogen peroxide is less toxic than superoxide and this hydrogen peroxide can be converted into water by enzymes like catalyze or peroxidase and they are harmless and in normal metabolism plants can accumulate these super oxides in chloroplast mitochondria paroxysm the internal component of the cell but the plants also have a mechanism to generate this reactive species says outside the cell when they are under stress so like pathogen infection is a stress there can be other stresses as well like drought for example UV light high temperature there are also stresses which can generate reactive oxygen species and this diagram shows that there is an a molecule cluster of enzymes called NADPH oxidase that can reduce oxygen to make it a super oxide and that takes place outside of the cell so this is plasma membrane the down blue color is inside the cell and above is the outside yourself and this house the reactive oxygen species says which has generated outside yourself plays a very important role in plant for a long distance signal transport so maybe I can skip that so hot roll this Ross place this Ross plays very important role because sometimes it can be harmful to microbes and Ross can oxidize membrane lipids that say generate a signal and Ross can also function as a long-distance signal so like this cartoon here it shows that this every tiny yellow dot on the leaf on the cell surface is the NADPH oxidase so who him there is just stress like it’s stimuli given in the arrow it generates NADPH oxidase activities NADPH oxidase generate Ross and that Ross can further activate the NADPH oxidase in the next cell and that Ross can generate in the activity in the next cell so eventually there is a propagation of reactive oxygen species from cell to cell as shown in scar on and it has been very nicely demonstrated in paper that you know within five minutes like you can see this color like this bright color over on a plant tells you how Ross travels so within five minutes the Ross can travel almost half of the plant and within 30 minutes can travel travel in their plant length so that is how the

Ross generated outside the plant cell helps in the propagation of the signal so next point is hypersensitivity response that’s a program cell death and as I told you at the beginning that this program cell death is not a universal feature but it takes place when there is a combination of RF here or the gene for gene combination and this mostly takes place when there is a bio traffic infections so what happens actually anyway even if you say by traffic or in a pro traffic the plants need a living cells to begin with it’s their growth because the not plants re pathogens see these pathogens are not sacrifice they need a living tissue to interact to understand the host surface and what happens hi persons B response is a very rapid program cell death so before pathogens probably can initiate their own growth plants kill their own cells surrounding so this is the tobacco leaf what source HR caused by DMV to echo mosaic virus these cells are killed by the plants itself so the virus cannot grow any further so this is how hypersensitivity response helps to contain microbial pathogens this wait is that it is also believed that HR is not only a causing a physical problem for the microbes this is also provide such a source of signal and that rest of the plant understand that a part of it gets got infection and become ready so HR or high personal response is it also source of a signal for immune response this is also HR a bite their tail in tobacco and this is HR on the model plant and a bit of C’s so what happens earlier I showed you the plank bizzy’s resistance or this is our society of plant disease resistance now you can see these leaves are turning yellow and this is slow death this death takes place over a period of say two to three days in contrast this HR is a rapid cell death the nature takes place within 10 hours to 12 hours and by that time bacteria might have not grown enough to enough for the plant scale there were cells before the bacteria canonist initiate their own growth and they’re so HR health now see this HR is a program cell death and when many of the biology students when eight programs hell death is spoken to them the first thing that strikes their mind is kalapa crosses apoptosis is a program cell death mostly demonstrated in case of animal cells and that shows apoptotic bodies like fragmentation of cell fragments an of DNA and good amount of literature shows a analogies between HR and apoptosis this figure shows a tomato product plus undergoing apoptosis and you can see this DNA fragmentation by tomato cells undergoing apoptosis with fungal DNA and this apoptotic DNA lengths are very similar that what you find in case of plants and this is also source a morphological feature of tomato protoplast under growing h are these plants this tomato cells here are treated with the pathogen which can lead to HR now you can see this top panel has been stained for DNA fragmentation and bottom panel for DNA staining so you can see that as the nature progressed over the time DNA gets fragmented and also the whole cells get fragmented typically like apoptotic bodies this in animal cell this caspase is there are many kind of caspases which are important for making a purposes and in plants of such Mazzone that many animal apoptotic inhibitors also can block hypersensitive response in plant

like in this case it has been shown that human caspase-1 inhibitor application can specifically block hypersensitive response generated by tobacco mosaic virus on tobacco HEV generated by tobacco mosaic virus in tomato so this data suggests that a large number of factors which control cell death between plant and animal are highly conserved so now we’ll come and speak about part about transcriptional programming this is the largest component plant immune response and a large amount of data available in the research articles so I’ll speak some key features of these transcriptional reprogramming components and this is carried out by hormones trans activator proteins transcription factors mediator proteins or mediator complexes that modulate transcription factor and epigenetic regulations that also modulate transcription the hormones there are plant hormones like salicylic acid ethylene and this morning acid these are the hormones which are called or is a different sermons they have also role in normal plant metabolism but when plants are under challenge these hormones come into play and provide resistance against pathogen so this cartoon tells you that a different kind of microbes be it in the fungus or a bacterial cell wall or effector triggers inside the cell can activate expression of a gene which I have turned here is called IC s1 with IC s1 stands for also corrects MEK synthetase one and thats a by synthetic enzyme for salicylic acid by synthesis so what happens that this presence of the microbes can activate salicylic acid biosynthesis and in turn that salicylic acid would turn on other genes which are important for immune response so this is the broadly how salicylic acid signal transaction takes place there is a protein called NP R 1 and this protein is activated by salicylic acid it can bind salicylic acid and that carries the signal inside the host cell and inside the host cell in the interacts with other transcription factor and together it can activate the defense response genes so here there are two cells which are drawn the lips cell cell in the left side is a resting cell where pathogen is not challenging so when the person is not challenged salicylic acid will be low and in the absence of salicylic acid there are large and order of negative regulators which repress or suppress the expression of Defense James it’s very very important that genes which are important for immune response should not be turned on when it is not required so plant employ a good number of proteins and to suppress their expression however her in a plant get infected the cell which is shown in the right side they accumulate salicylic acid when salicylic acid is accumulated then the protein like in PR one which I told you can interact with many transcription factors some of them are called like digit transcription factor some of them are called as a work d transcription factor this work e DGA NP r– one all together can modulate transcription of a large number of genes and which eventually would activist difference response so this is a summary you can say four different kind of immune response that are activated by these three hormones salicylic acid ethylene and Jase monic acid and their signaling pathways are not completely independent of each other there is a interdependence both energetic interaction and antagonistic interaction and with the

help of it their combined effort with these hormones turn-on expression of a large number of genes in the right hand side I have shown you some of the genes name these are called pathogenesis related protein so as I told you earlier these pure proteins are often antibiotic and they can suppress the growth of microbe some of the pure proteins are very specific for a particular type of hormone like for example PR one is a protein that is induced by only salicylic acid and like here PR 3 is induced only by ethylene and a protein called PSP or vegetative storage protein are induced only by G’s folic acid so these proteins are monitored much easier than monitoring the hormone itself like for example measuring amount of salicylic acid or measuring the ethier in a cell is more difficult than measuring transcript level of PR 1 or PR 3 like there are many ways you can measure transcript one of the common mechanism is a piece here so PCR is known is a common technique it’s known to all biology students with the help of a piece here you can understand how much transcript is accumulated so starting the accumulation of a transcript appear one can also suggest how much salicylic acid signal has been activated and so on and here is one PDF 1.2 has been shown here that is activated by both ethan and just Monica’s in PDF 1.2 is a antibiotic peptide which is homologous to drew so my scene of Drosophila so drew so my scene is an antibiotic peptide made in flies and plans for Malaga is called PDF 1.2 that is antimicrobial and it’s activist and takes place mostly by just Monica said with the help of ethylene signaling as well so this is very broad of hormone signaling like when a plant is infected by a pathogen it accumulates hormones like salicylic acid ethylene just Monica seed and their accumulation lead to activation of transcription factors like I told you TGA Varkey and transcripts an activator like NPR one and that lead to synthesis of phytochemicals and as well as antibiotic peptides so this is a vital axial molecules they are all free onyx they’re like camel acts in Reverse Atal reservatol matrix see methylene so they are the molecules which are antimicrobial and can can kill micro and when they’re added in in vitro culture also this is a figure from a paper which shows you the expression of a large varieties of pure proteins so this is tmv tobacco mosaic virus infected plant and these pure proteins are expressed in the infected plants and the left hand column is non infected so when pathogen is not infected this pure proteins are not induced but when plants are infected by the pathogen they accumulate these pair proteins so in addition to pure proteins or this vital axis accumulations plants also throw them outside because you know as I told you most of the micros are growing outside so in order to suppress the growth plant secret those molecules outside the cell with the help of the molecules like exocytosis pathway it can secret those antibiotic peptide or phenolic molecules higher the pathogen is growing so here like this pathogen this would be inhibited by these molecules which are thrown by the cell outside and this is the pattern recognition receptors this is the kind of a summary I can tell you that this is the there are receptors which are outside the cells inside your cell and working on the transcriptions and eventually the it is activating immune response okay so

there can be two situations so I’ll one situations is that this is my last slide and so I will try to give up a summary that so far what I have told you about how different of immune systems are and how they can be compared with the cases depending on their recognition like the plant can be infected by pathogen these pathogens are tiny dots which I have so I am showing here with the tip of this mouse and this you can think about a large plant cell and this triangle is a plant toxin molecule or effector molecule or also call it a virulent factor so this molecules are effector molecules are released inside the host and once it is inside the host plants can either recognize it or it can fail to recognize so in the left side this is a plant which can recognize and the right side is a plant which cannot recognize because this recognition system is different which is not fit for this one so in this case there will be second messengers second messengers like as I told you hormones salicylic acid ethylene this morning acid and that would activate a very strong immune response and a resistance however if it is not detected then also you see immune response and that is mediated by pattern trigger immunity or PTI this pattern triggered immunity or prettier is strong is not strong as a TI but strong enough for widget of the pathogens here only thing happens that defense response is delayed so when defense response is delayed if the pathogen is capable of growing it will grow and plant become susceptible so maybe sometimes as some other day if I can get a chance elf to speak about it that in the plants also have a strong memory system formation the plant once they’re infected can generate an infection memory and that usually depends on a successful resistance mechanism so especially when there is an array very combinations plant can pretty quickly suppress the growth of pathogens so in such cases plants can generate a sort of infection memory that infection memory helps the plants to show a much stronger response when they’re challenged subsequently so during subsequent challenge actually almost pathogens cannot grow and plants a resistance make is very strong which units college system encode resistance okay thank you with this note thank you sir thank you so very much you delivered such a nice lecture I could relate some of the things which I have known or which I have not even but as you said that in future lectures we would of course can talk about the memory system in plants as we talked about the immune system of plants thank you sir thank you so very much for being with us and giving your precious time to this lecture thank you thank you so much you