Tomato plants inhibitors

Plant growth inhibitor. Water extract of the aerial parts, administered externally, was toxic to tomato plant seedlings . 

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... 

Direction of flow of PIIF. The time-course of Inhibitor I accumulation In leaves of young tomato plants at the four leaf stage, wounded at 0 time and at 72 hr. Is shown In Fig. 1. Wounding of an upper leaflet (left) did not cause accumulation... 

Figure 1. Time course of accumulation of Inhibitor I in terminal leaflets of young tomato plants. Leaves were wounded at the uppermost leaf (left) and the lowest leaf (right) by crushing across the midrib of the terminal leaflet with a hemostat at zero time and again at 72 h. The concentrations of Inhibitor I in leaves were determined immunologically.

INHIBITOR I ACCUMULATION IN LEAVES OF YOUNG TOMATO PLANTS 120 HOURS FOLLOWING WOUNDING OF INDIVIDUAL LEAVES AT DIFFERENT LOCATIONS ON THE PLANTS... 

Young tomato plants having four leaves were wounded at the leaf position shown below with a hemostat at 0 and 72 hr. After 120 hr following the initial wounding the terminal leaflet of each leaf was assayed for Inhibitor I concentration. 

Figure 2. Left Inhibitor I accumulation in leaves of wounded young tomato plants. The middle leaf of young tomato plants at the three leaf stage was wounded at zero time and excised at the times shown. Inhibitor I in the upper and lower intact leaves was determined immunologically 48 h following wounding. Right 5 /xL of glucose (specific activity, 28 Ci/mM) was applied directly...

We subjected a segment of the petiole of the lowest leaf of several 3 leaf stage tomato plants, to a hot air jet to destroy the phloem. Within an hour the Injured petiole segments had dried to form the thin strands of xylem. As before, this treatment did not release PIIF Into the plant (Table II, treatment 3) while the leaf Itself (leaf 1) accumulated considerable Inhibitor I. Subsequent wounding of leaves whose phloem had been destroyed (Table II, treatment 4) did not result In Inhibitor I accumulation In adjacent leaves. Indicating that the phloem destruction had blocked Its transport out of the wounded leaf. 

All treatments of young tomato plants (having three leaves) were at the lowest leaf ( 1) shown below. Hot air (80 C) was applied to the base of the petiole through a window in a teflon shield to destroy a segment of phloem tissue. A single wound, perpendicular to the midrib was inflicted at the center of the terminal leaflet of leaf 1 three days after hot air treatment and Inhibitor I levels were assayed in the leaves 24 hr later. 

Messenger RMA has been prepared from leaves of wounded and unwounded tomato plants and only leaves of wounded plants contain translatable mRNAs specific for Inhibitors I and II... 

Figure 4. Time course analysis of the accumulation of Inhibitors I and II protein, translatable mRNAs and apparent translational efficiencies in leaves of singly and doubly wounded tomato plants. Key — —, Inhibitor I, single wound —O—, Inhibitor II, single wound — 9 —, Inhibitor I, double wound and — O —, Inhibitor II, double wound.

Figure 5. Size analysis of Inhibitors I and 11 specific mRNA from levels of 9- and 18-h singly wounded tomato plants and 18-h doubly wounded plants. Poly(A ) RNA was applied to 15-30% linear sucrose gradients and was spun at 25,000 rpm. Twenty-five fractions were collected, the absorbency was measured, and the mRNA was precipitated by cold ethanol. In vitro translations were performed with each fraction in a rabbit reticulocyte system, and isolation of the preinhibitors with preformed antibody precipitates located the position of the two inhibitors. The gradients were calibrated by centrifugation of tomato leaf polyfA)" RNA on an identical gradient. The locations of translatable mRNAs for Inhibitors I and II were identical with RNA obtained from 9- and 18-h singly wounded or 18-h doubly...

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. 

Peng, J.H. Black, L.L. (1976) Increased Proteinase Inhibitor Activity in Response to Infection of Resistant Tomato Plants by Phytophthora infestans. Phytopathology 66, 958-963. 

We will discuss selected current knowledge on the use of plant enzymes as bases of insect resistance the review is not comprehensive. Particular attention will be given to induced de novo synthesis of proteinase inhibitors in the tomato plant Lvcop-ersicon esculentum, and on the simultaneous use of plant polyphenol oxidases as a means of conferring resistance to insect pests. 

Table V. The Effect of Tomato Plant Foliar Polyphenol Oxidase Activity on Proteinase Inhibitors in Snodoptera exigua...

Compatibility with Human Health. Many biochemical factors of resistance against insects and pathogens can constitute a health hazard for human consumers (19,61,109,131). But in the tomato plant, the use of proteinase inhibitors, phenolics, and/or PPO as bases of resistance appears compatible with human health because a) tomato fruit is not consumed in quantities sufficient to lead to acute or chronic poisoning, and b) at the time of ripening these substances are substantially or completely absent from the fruit (132 Felton and Duffey, unpublished data). 

In foliage, the concentrations of serine proteinase inhibitors are lower than that in seeds however, the induction of serine proteinase inhibitors has been reported in many plants including tobacco and tomato, and the inhibitors have been proven to function as a plant defense system.79-81 Leaf damage by the tobacco hornworm Manduca sexta was much bigger in tomato plant line deficient in proteinase inhibitor induction than in those that can induce proteinase inhibitor on herbivory.82... 

Oligogalacturonides have been suggested to act as mobile wound hormones, switching on the synthesis of protease inhibitors in several leaves of a tomato plant in response to a localised injury in one leaf [56]. In experiments carried out to test the mobility of pectic fragments within the plant, exogenous C-labelled pectic polysaccharides and H-labelled oligogalacturonides were applied to wound-sites on tomato leaves. The radioactivity moved towards the tip and margins of the leaf (a pattern characteristic of the xylem stream... 

The damage to leaf surfaces in tomato plants leads to the biosynthesis of protease inhibitors, which interfere with the digestive system of the infesting insects and restrict the availability of essential amino acids, eventually retarding growth and development of the pests. 

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-... 

Protease inhibitors are naturally present in plant foods, especially in legume seeds, but they also occur in cereals and some other plant materials (such as potatoes and tomatoes). Protease inhibitors of microbial and animal origins also exist. In plants, protease inhibitors fulfill several functions. They probably serve as a cytosol... 

Miscellaneous Identified Inhibitors. 3-Acetyl-6-methoxy-benzaldehyde is present in the leaves of the desert shrub Encelia farinosa. It is apparently leached from the leaves and washed into the soil by rain. Concentrations of approximately 0.5 mg. per gram of dried leaf material have been measured. In sand culture studies, growth of tomato seedlings was inhibited by 50 p.p.m. while 115 p.p.m. reduced growth by 50% (53). A concentration of 250 p.p.m. killed the test plants within one day. The structure was confirmed by synthesis, and the synthetic material was shown to be as active as the natural product (54). Derivatives were also prepared in which a cyano, nitro, or amino group was substituted for the aldehyde moiety. The amino derivative was reported to be the most highly toxic. 

Inhibition of tomato and barley plants growing in soils infested with Centaurea repens (knapweed) was reported by Fletcher and Renney (38). A toxic component was isolated in highest concentration from the foliage of knapweed. The inhibitor was considered to be an indole alkaloid or auxin precursor because of its ultraviolet absorption spectrum and the positive reactions obtained with Salkowski and Ehrlich reagents. The presence of the inhibitor was considered to explain partially the rapid establishment of Centaura spp. in almost pure stands. 

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