Recent developments in the metabolism and function of polyamines in plants is presented Polyamines appear to be involved in a wide range of plant processes, however their exact role is not completely understood In this review, the metabolic pathways involved in polyamine biosynthesis and degradation are explained, along with the transport and conjugation of these compounds The studies involved in the understanding of function(s) of polyamines using metabolic inhibitors, as well as genetic and molecular approaches are described Polyamine metabolism and profound changes in polyamine titres in response to infection by pathogens has been presented Its role in adaptation of plants to stress is also presented Molecular understanding of polyamines and their modulation in transgenics is also discussed Further line of work in the understanding of the role of polyamines has also been focussed

Role of polyamines in the ontogeny of plants and their biotechnological applications

Plant polyamines in flowering and fruit ripening

Fruits of tomato, Lycopersicon esculentum Mill. cv Liberty, ripen slowly and have a prolonged keeping quality. Ethylene production and the levels of polyamines in pericarp of cv Liberty, Pik Red, and Rutgers were measured in relation to fruit development. Depending on the stage of fruit development, Liberty produced between 16 and 38% of the ethylene produced by Pik Red and Rutgers. The polyamines putrescine, spermidine, and spermine were present in all cultivars. Cadaverine was detected only in Rutgers. Levels of putrescine and spermidine declined between the immature and mature green stages of development and prior to the onset of climacteric ethylene production. In Pik Red and Rutgers, the decline persisted, whereas in Liberty, the putrescine level increased during ripening. Ripe pericarp of Liberty contained about three and six times more free (unconjugated) polyamines than Pik Red and Rutgers, respectively. No pronounced changes in spermidine or cadaverine occurred during ripening. The increase in the free polyamine level in ripe pericarp of Liberty may account for the reduction of climacteric ethylene production, and prolonged storage life.

Polyamine levels and tomato fruit development: possible interaction with ethylene.

The diamine putrescine and the polyamines spermidine and spermine are amino acid-derived, aliphatic nitrogenous compounds of wide distribution among plant cells (Fig1) The earliest reference to polyamines in the scientific literature is van Leeuwenhoek’s classic letter to the Royal Society of London in 1678 During his studies describing spermatozoa, he observed the gradual formation of colorless crystals upon drying the samples The correct structure of these crystals, which corresponded to spermine, was not determined until over 250 years later1 Spermidine was later found in mammalian tissues The related diamines putrescine and cadaverine were found in decomposing animal and vegetable matter as a result of microbial activity Within this historical frame, it is not surprising that earlier studies on these compounds were done mostly on non-plant systems Recent interest in the function of polyamines in higher plants is in good part derived from discoveries in microbial and animal cells

Primary and Secondary Metabolism of Polyamines in Plants

Fruit firmness, free polyamine levels (putrescine, spermidine, and spermine), abscisic acid (ABA), and color index were determined in lemon fruit at two ripening stages (at color break and fully yellow) after vacuum infiltration with 1mM putrescine and 1 mM calcium chloride. Both treatments significantly increased fruit firmness as compared with control fruit in stage 1 lemons. Putrescine-treated fruits showed higher levels of firmness and lower weight loss than calcium-treated or nontreated fruits during storage. The concentrations of putrescine, spermidine, and spermine were higher in stage 1 than in stage 2 lemons, whereas the opposite was found for ABA. The treatment with putrescine was the most effective to maintain higher levels of endogenous putrescine and spermidine, but only for stage 2 fruit. Both putrescine and calcium treatments delayed the color change, which was related to the lowest levels of ABA found. Keywords: Lemon; Citrus lemon; polyamines; abscisic acid; postharvest; firmness; color

Influence of Postharvest Treatment with Putrescine and Calcium on Endogenous Polyamines, Firmness, and Abscisic Acid in Lemon (Citrus lemon L. Burm Cv. Verna)

Changes in activity of polyamine biosynthetic enzymes and in polyamine contents in developing fruit tissues of ‘Murcott’ mandarin

This datasheet on Entamoeba invadens covers Identity, Distribution, Hosts/Species Affected.

R. Nathan

Papers

Changes in activity of polyamine biosynthetic enzymes and in polyamine contents in developing fruit tissues of ‘Murcott’ mandarin

Entamoeba invadens