Article de synthese sur le role des polyamines durant les phases de croissance et de developpement: division cellulaire embryogenese, rhizogenese, floraison et croissance du tube pollinique. Etude des relations entre polyamines et regulateurs de croissance des plantes

Do polyamines have roles in plant development

Some characteristics and applications of a transglutaminase, derived from a variant of Streptoverticillium mobaraense, namely microbial transglutaminase (MTGase), are considered MTGase, mass-produced at low cost by fermentation, catalyses the crosslinking of most food proteins through the formation of an e-(γ-glutamyl)lysine bond, in the same way as well-known mammalian enzymes However, MTGase is remarkable because it is calcium independent and its molecular weight is smaller than that of other known enzymes The results of many studies suggest that MTGase, as well as other transglutaminases, has many potential applications in food processing and in other areas

Transglutaminase and its use for food processing

Recent advances in the understanding of the molecular basis of plant response to ozone attack are reviewed. Plants grown in elevated atmospheric ozone are known to undergo several biochemical changes before any actual damage can be detected. These reactions include increases in the activities of enzymes associated with general plant defence mechanisms. Ozone exposure often causes a surge in the production of the plant hormone ethylene, as well as changes in polyamine metabolism and increases in the activities of several phenylpropanoid and flavonoid pathway enzymes. The activities of superoxide dismutase and peroxidases that protect cells from the oxidative damage caused by hydroxyl radicals, H2O2 and superoxides also increase. However, ozone-induced changes in plant cells at the gene level are almost unknown. The limited data available suggest close similarities between ozone-induced and pathogen-induced defence responses in plants. Several general defence genes that have been cloned in other studies will soon be applied to studies of gene expression in ozone-exposed plants. The use of molecular biological tools in ozone research should enable the development of highly specific and sensitive molecular markers for biomonitoring ozone-induced injuries in plants.

Plant defence systems induced by ozone

The effect of the ethylene antagonists norbornadiene and silver nitrate and the ethylene precursor l-aminocyclopropane-l-carboxylic acid (ACC) on Zea mays plant regeneration was studied. A 12-fold increase in plant regeneration, as measured by number of plants obtained per gram fresh weight from callus cultures of maize inbreds Pa91 and H99, was obtained by 250 μM norbornadiene and 100 μM silver nitrate treatments. An increase in amout of nonregenerable tissue and a 68% decrease in plant regeneration were associated with callus treated with 1 mM ACC. Ethylene emanation from 1 mM ACC treated callus reached a maximum of 170 nl g−1 h−1 after 3 days compared to 7 nl g−1 h−1 for the control. The free proline content was up to 80% lower in 1 mM ACC treated callus grown for 30 days on medium with or without 12 mM proline, respectively, as compared to each control. These studies indicate that ethylene action inhibitors such as norbornadiene and silver nitrate can be used to increase plant regeneration efficiency from maize callus cultures.

Effect of l-aminocyclopropane-l-carboxylic acid, silver nitrate, and norbornadiene on plant regeneration from maize callus cultures.

Transglutaminase is an enzyme that forms crosslinks between protein molecules. This crosslinkage has unique effects on protein properties, gelation capability, thermal stability, water-holding capacity, etc. A transglutaminase has been isolated from Streptoverticillium sp., and its practical use in the food industry realized. Transglutaminase is now widely used in seafood, surimi products, meat products, noodles/pasta, dairy products, baked goods, and so on. It has great potential to improve the firmness, elasticity, viscosity, heat stability, and water-holding capacity of prepared foods through the mild enzyme reaction. The overall applications of transglutaminase in the food industry are reviewed.

Transglutaminase: its utilization in the food industry

An extract prepared from the apical meristematic region of etiolated pea seedlings was able to catalyze the incorporation of putrescine into trichloroacetic acid precipitable material. The enzyme was found to be soluble and followed a typical Michaelis-Menten kinetics when N-N-dimethyl casein was used as a substrate. Its activity was promoted by Ca2+ and inhibited by Cu2+ and dl-dithiothreitol. Other polyamines competed with putrescine as substrates and cadaverine was the most potent inhibitor of putrescine incorporation. Plant transglutaminase is capable of recognizing specific sites in substrates described for animal transglutaminase, like insulin, fibrinogen, pepsin, and thrombin. However, it can also use as substrates cellulase and creatine kinase which have not been described for transglutaminase from other sources.

Evidence for transglutaminase activity in plant tissue

Activity of arginine decarboxylase in etiolated pea seedlings appears 24 hours after seed imbibition, reaches its highest level on the 4th day, and levels off until the 7th day This activity was found in the apical and subapical tissue of the roots and shoots where intensive DNA synthesis occurs Exposure of the seedlings to ethylene greatly reduced the specific activity of this enzyme The inhibition was observed within 30 min of the hormone application, and maximal effect-90% inhibition-after 18 hours Ethylene at physiological concentrations affected the enzyme activity; 50% inhibitory rate was recorded at 012 microliters per liter ethylene and maximal response at 12 microliters per liter Ethylene provoked a 5-fold increase in the K(m) (app) of arginine decarboxylase for its substrate and reduced the V(max) (app) by 10-fold However, the enzyme recovered from the inhibition and regained control activity 7 hours after transferral of the seedlings to ethylene-free atmosphere Reducing the endogenous level of ethylene in the tissue by hypobaric pressure, or by exposure to light, as well as interfering with ethylene action by treatment with silver thiosulfate or 2,5-norbornadiene, caused a gradual increase in the specific activity of arginine decarboxylase in the apical tissue of the etiolated seedlings On the basis of these findings, the possible control of arginine decarboxylase activity by endogenous ethylene, and its implication for the hormone effect on plant growth, are discussed

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Control by ethylene of arginine decarboxylase activity in pea seedlings and its implication for hormonal regulation of plant growth.

Influence of Ethylene on S-adenosylmethionine Decarboxylase Activity in Etiolated Pea Seedlings

Exposing etiolated pea seedlings to ethylene which inhibited the activity of arginine decarboxylase and S-adenosylmethionine decarboxylase caused an increase in the level of cadaverine. The elevated level of cadaverine resulted from an increase in lysine decarboxylase activity in the tissue exposed to ethylene. The hormone did not affect the apparent Km of the enzyme, but the apparent Vmax was increased by 96%. While lysine decarboxylase activity in the ethylene-treated plants increased in both the meristematic and the elongation zone tissue, cadaverine accumulation was observed in the latter only. The enhancement by ethylene of the enzyme activity was reversed completely 24 hours after transferring the plants to an ethylene-free atmosphere. It is postulated that the increase in lysine decarboxylase activity, and the consequent accumulation of cadaverine in ethylene-treated plants, is of a compensatory nature as a response to the inhibition of arginine and S-adenosylmethionine decarboxylase activity provoked by ethylene.

Inhibition by ethylene of polyamine biosynthetic enzymes enhanced lysine decarboxylase activity and cadaverine accumulation in pea seedlings.

Applied diamines and polyamines inhibited the incorporation of radioactively labeled leucine and uridine into trichloroacetic acid-insoluble material in apple (Malus domestica Borkh, cv Golden Delicious) fruit tissue. The inhibitory effect was in general more pronounced with the higher molecular weight amines. Putrescine at 5 millimolar inhibited leucine incorporation by 37% and uridine by 44%. Spermidine and spermine at the same concentration inhibited uridine incorporation by 60%. The polyamines at concentrations between 0.1 and 1.0 millimolar inhibited leucine incorporation by 55 to 90%. The inhibitory effect of 0.1 to 10 millimolar polyamines on dark- and wound-induced senescence or ethylene production, is discussed in the light of interference with macromolecular synthesis.

Isaac Icekson

Papers

Evidence for transglutaminase activity in plant tissue

Control by ethylene of arginine decarboxylase activity in pea seedlings and its implication for hormonal regulation of plant growth.

Influence of Ethylene on S-adenosylmethionine Decarboxylase Activity in Etiolated Pea Seedlings

Inhibition by ethylene of polyamine biosynthetic enzymes enhanced lysine decarboxylase activity and cadaverine accumulation in pea seedlings.

Inhibition by polyamines of macromolecular synthesis and its implication for ethylene production and senescence processes.