of proteins. When a part of a plant becomes infected with a microbial or viral pathogen, in case of an incompatible interaction triggered by specific elicitors, the plant produces a localized hypersensitive response (HR), in which cells at the site of infection undergo rapid apoptosis to prevent spread to other parts of the plant. HR has some similarities to animal pyroptosis, such as a requirement of caspase-1-like proteolytic activity of VPEγ, a cysteine protease that regulates cell disassembly during cell death. "Resistance" (R) proteins, encoded by R genes, are widely present in plants and detect pathogens. These proteins contain domains similar to the NOD Like Receptors and TLRs. Systemic acquired resistance (SAR) is a type of defensive response that renders the entire plant resistant to a broad spectrum of infectious agents. SAR involves the production of chemical messengers, such as salicylic acid or jasmonic acid. Some of these travel through the plant and signal other cells to produce defensive compounds to protect uninfected parts, e.g., leaves. Salicylic acid itself, although indispensable for expression of SAR, is not the translocated signal responsible for the systemic response. Recent evidence indicates a role for jasmonates in transmission of the signal to distal portions of the plant. RNA silencing mechanisms are important in the plant systemic response, as they can block virus replication. The jasmonic acid response is stimulated in leaves damaged by insects, and involves the production of methyl jasmonate. See also Apoptosis Innate lymphoid cell NOD-like receptor Endothelial cell tropism References External links system Innate Immune System Animation XVIVO Scientific Animation Immune system Insect immunity