Preformed plant defenses

Osbourn, A.E. Preformed antimicrobial compounds and plant defense against fungal attack. Plant Cell 1996 8 1821-1831. 

Plant Defense Preformed and Induced Resin Defense by Pine Trees (Original Contribution by Fred Stephen, Department of Entomology, University of Arkansas and Timothy D. Paine, Department of Entomology, University of California, Riverside)... 

Plants have evolved different mechanisms to protect themselves against a great variety of invasive pathogens. As a part of the defense, plants produce a number of secondary metabolites with antimicrobial activity. Many of these compounds are produced constitutively, being present in healthy plants as normal metabolic products. VanEtten et al. proposed the term "phytoanticipin" to define these preformed antimicrobial... 

It is envisioned that the defensive systems of plants include preformed physical and chemical barriers as well as inducible defenses that also can be either physical or chemical. An example of an inducible defense is the synthesis of specific antimicrobial compounds such as phytoalexins or phytoanticipins. However, in other instances plants react to pests by developing long-lasting, broad-spectrum systemic resistance to later attacks by pathogens. This type of resistance is referred to as systemic acquired resistance, and was discovered in tobacco by Ross (1961). This form of resistance is almost universally... 

In preformed defenses the plant invests considerable energy and other metabolic resources in a generalized defense against some stresses that may never materialize. 

Another compound bordering between preformed and induced defenses is gossypol. This compound accumulates within epidermal glands on the surface of cotton plants and is very toxic to some insects [ .]. Gossypol, and a series of structurally related compounds on the same biosynthetic pathway, accumulate to substantially increased levels in plants that have been challenged by potential pathogens. For this reason they have been considered phytoalexins by some plant pathologists. Phytoalexins are inducible antibiotics and will be discussed later. 

Like the benzoxazinones, cyanogenic glucosides belong to the preformed defense of the plant and are stored in the vacuole. Upon disruption of the plant tissue, they are degraded by P"glucosidases to the corresponding a-hydrox-ynitriles, which are hydrolyzed by a-hydroxynitrile lyases to aldehydes or ketones and toxic hydrogen cyanide (HCN) (Fig. 13). Since the a-hydroxynitriles are unstable, they can also... 

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