Tomato plants wounded, proteinase inhibitors

Regulation of Synthesis and Accumulation of Proteinase Inhibitors in Leaves of Wounded Tomato Plants... 

Two proteinase inhibitors, Inhibitors I and II, accumulate in leaves of tomato plants when attacked by chewing Insects or mechanically wounded. The accumulation of these two antinutrient proteins is apparently a defense response and is initiated by the release of a putative wound hormone called the proteinase Inhibitor inducing factor (PIIF). The direction of flow of PIIF out of wounded leaves is primarily towards the apex and transport occurs maximally about 120 min following wounding. After a single severe wound, the vitro translatable tomato leaf mRNA specific for Inhibitors I and II Increases to a maximum within four hours and remains constant for about five hours when it decreases rapidly to about 50% of the maximum. 

A severe mechanical wound on a single leaf of tomato plants initiates a complex series of extracellular and intracellular reactions which result in the synthesis and accumulation of two proteinase Inhibitors, Inhibitors I and II, in leaf cells (J, 2. A second wounding, within a few hours, results in a 2-3 fold Increase in the rates of accumulation initiated by the... 

The wound-induced synthesis and accumulation of proteinase Inhibitors I and II in tomato leaves has provided a model system to study the regulation of proteinase inhibitor genes in plants. The simplicity of the phenomenon has made it possible to Isolate the wound-factor, or hormone, and to study its release, direction and rate of transport in tomato plants. Messenger RNA has been isolated from leaves of wounded plants and contains translatable mRNAs for the two proteinase inhibitors. Studies with these mRNAs have provided a basis for the initiation of a program to clone inhibitor cDNAs for studies of the molecular basis of the wound-Induced process of inhibitor synthesis. 

Another putative hormone involved in pathogen resistance in plants is the peptide systemin [104] (Fig. If). This 18-amino acid peptide is produced from a much longer precursor, called prosystemin, upon wounding of tomato leaves, and induces proteinase inhibitors I and II in adjacent leaves. Wounding also induces the synthesis of the precursor, prosystemin. Systemin overproduction by roots induces the proteinase inhibitors constitutively in all parts of the plant, while the antisense gene for prosystemin inhibits the development of pathogen resistance [105]. The action of systemin may be via synthesis of JA, which acts as a second messenger in the induction of the proteinase inhibitors [104]. 

When methyl jasmonate was applied to the surface of tomato plants, the synthesis of a defensive proteinase inhibitor protein was induced, not only in the plant to which the application was made but also in nearby plants. In subsequent studies, this compound was shown to have a similar effect with plants of other families as well (Farmer and Ryan, 1990 Pearce et al., 1991). In a series of experiments, it was demonstrated that methyl jasmonate can be a component of interplant communication systems. Octadecanoid precursors of jasmonic acid were able to activate the synthesis of wound-inducible proteinase inhibitors (Crombie and Mistry, 1991 Farmer and Ryan, 1992). Jasmonic acid is a signal transducer in elicitor-induced plant cultures of Rauvolfia canescens and Eschscholtzia californica. Tissue cultures of 36 species of plants could be induced to accumulate second-... 

---