Induced Systemic Resistance (ISR) is a resistance mechanism in

plant Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclud ...

s that is activated by

infection An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dise ...

. Its mode of action does not depend on direct killing or inhibition of the invading

pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...

, but rather on increasing

physical Physical may refer to: *Physical examination In a physical examination, medical examination, or clinical examination, a medical practitioner examines a patient for any possible medical signs or symptoms of a medical condition. It generally co ...

chemical A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add that chemical substance cannot be separated into its constituent elements by physical separation methods, i.e., wi ...

barrier of the

host A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places * Host, Pennsylvania, a village in Berks County People *Jim Host (born 1937), American businessman * Michel Host ...

plant. Like the Systemic Acquired Resistance (SAR) a plant can develop defenses against an invader such as a pathogen or parasite if an infection takes place. In contrast to SAR which is triggered by the accumulation of

salicylic acid Salicylic acid is an organic compound with the formula HOC6H4CO2H. A colorless, bitter-tasting solid, it is a precursor to and a metabolite of aspirin (acetylsalicylic acid). It is a plant hormone, and has been listed by the EPA Toxic Substance ...

, ISR instead relies on

signal transduction Signal transduction is the process by which a chemical or physical signal is transmitted through a cell as a series of molecular events, most commonly protein phosphorylation catalyzed by protein kinases, which ultimately results in a cellula ...

pathways activated by

jasmonate Jasmonate (JA) and its derivatives are lipid-based plant hormones that regulate a wide range of processes in plants, ranging from growth and photosynthesis to reproductive development. In particular, JAs are critical for plant defense against herb ...

and

ethylene Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon-carbon double bonds). Ethylene i ...

Discovery

The induction of plant-induced resistance to pathogen protection was identified in 1901 and was described as the "system of acquired resistance." Subsequently, several different terms have been used, namely, "acquired physiological immunity", "resistance displacement", "plant immune function" and "induced system resistance." Many forms of stimulus have been found to induce the plant to the virus, bacteria and fungi and other disease resistance including Mechanical factors (

dry ice Dry ice is the solid form of carbon dioxide. It is commonly used for temporary refrigeration as CO2 does not have a liquid state at normal atmospheric pressure and sublimates directly from the solid state to the gas state. It is used primarily a ...

damage,

electromagnetic In physics, electromagnetism is an interaction that occurs between particles with electric charge. It is the second-strongest of the four fundamental interactions, after the strong force, and it is the dominant force in the interactions of a ...

ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...

, and low

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...

and high temperature treatment, etc.) Chemical factors ( heavy metal salts, water,

) and Biological factors (

fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

virus A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsky's 1 ...

es, and their

metabolite In biochemistry, a metabolite is an intermediate or end product of metabolism. The term is usually used for small molecules. Metabolites have various functions, including fuel, structure, signaling, stimulatory and inhibitory effects on enzymes, c ...

s).

Mode of action

Induced resistance of plants has 2 major modes of action: the SAR pathway and the ISR pathway. SAR can elicit a rapid local reaction, or

hypersensitive response Hypersensitive response (HR) is a mechanism used by plants to prevent the spread of infection by microbial pathogens. HR is characterized by the rapid death of cells in the local region surrounding an infection and it serves to restrict the growt ...

, the pathogen is limited to a small area of the site of

. As mentioned, salicylic acid is the mode of action for the SAR pathway. ISR enhances the defense systems of the plant by jasmonic acid (JA) mode of action. Both act on the effect of the NPR-1, but SAR utilizes PR genes. It is important to note that the two mediated responses have regulatory effects on one another. As SA goes up, it can inhibit the effect of JA. There is a balance to be maintained when activating both responses. ISR responses can be mediated by rhizobacteria which has shown to be effective against necrotrophic pathogens and insect herbivores that are sensitive to JA/ET defenses. The importance of rhizobacteria-mediated ISR has been widely reported. The biological factors of plant-induced system resistance generally include two broad categories, namely classical plant-induced resistance to disease induction (PGPR) or fungi that promote plant growth (PGPF), and plant growth-promoting

rhizosphere The rhizosphere is the narrow region of soil or substrate that is directly influenced by root secretions and associated soil microorganisms known as the root microbiome. Soil pores in the rhizosphere can contain many bacteria and other microor ...

bacteria (PGPR) or plant growth promoting fungi (PGPF). The difference is mainly due to the fact that the latter can effectively promote plant growth and increase crop yield while causing (or increasing) plant resistance to diseases (sometimes including

pests PESTS was an anonymous American activist group formed in 1986 to critique racism, tokenism, and exclusion in the art world. PESTS produced newsletters, posters, and other print material highlighting examples of discrimination in gallery represent ...

Effects on insects

Some studies have also reported negative effects of beneficial microbes on plant-insect interactions as well.

Applied research

To date, work on induction of plant systemic resistance has shown that inducing plant system resistance work has important implications for basic and applied research. Induced resistance applications in

melon A melon is any of various plants of the family Cucurbitaceae with sweet, edible, and fleshy fruit. The word "melon" can refer to either the plant or specifically to the fruit. Botanically, a melon is a kind of berry, specifically a "pepo". The ...

tobacco Tobacco is the common name of several plants in the genus '' Nicotiana'' of the family Solanaceae, and the general term for any product prepared from the cured leaves of these plants. More than 70 species of tobacco are known, but the ...

bean A bean is the seed of several plants in the family Fabaceae, which are used as vegetables for human or animal food. They can be cooked in many different ways, including boiling, frying, and baking, and are used in many traditional dishes th ...

potato The potato is a starchy food, a tuber of the plant ''Solanum tuberosum'' and is a root vegetable native to the Americas. The plant is a perennial in the nightshade family Solanaceae. Wild potato species can be found from the southern Unit ...

, and

rice Rice is the seed of the grass species ''Oryza sativa'' (Asian rice) or less commonly ''Oryza glaberrima ''Oryza glaberrima'', commonly known as African rice, is one of the two domesticated rice species. It was first domesticated and grown i ...

have achieved significant success. Over the past decade, the study of induced system resistance has become a very active field of research. Methods to artificially activate the ISR pathway is an active area of research. The research and application of inducing plant system resistance have been encouraging but are not yet a major factor in controlling plant pathogens. Incorporation into integrated pest management programs have shown some promising results. There is research regarding defense against leaf chewing insect pests, by the activation of jasmonic acid signalling triggered by root-associated microorganisms. Some ongoing research into ISR includes (1) how to systematically improve the selection of induction factors; (2) the injury of induced factors; (3) the phenomenon of multi-effect of induced factors; (4) the effects of chemical induction factors on environmental factors; (5) Establishment of population stability of multivariate biological inducible factor. Research into ISR is driven largely by a response to pesticide use including 1) Increasing resistance by pathogens to pesticides, 2) the necessity to remove some of the more toxic pesticides from the market, 3) health and environment problems caused as an effect of pesticide use, and 4) the inability of certain pesticides to control some pathogens.

References

{{Reflist Phytopathology Plant physiology Immune system

Discovery

Mode of action

Effects on insects

Applied research

See also

References