Early studies on plant polyamine research pointed to their involvement in responses to different environmental stresses. During the last few years, genetic, transcriptomic and metabolomic approaches have unravelled key functions of different polyamines in the regulation of abiotic stress tolerance. Nevertheless, the precise molecular mechanism(s) by which polyamines control plant responses to stress stimuli are largely unknown. Recent studies indicate that polyamine signalling is involved in direct interactions with different metabolic routes and intricate hormonal cross-talks. Here we discuss the integration of polyamines with other metabolic pathways by focusing on molecular mechanisms of their action in abiotic stress tolerance. Recent advances in the cross talk between polyamines and abscisic acid are discussed and integrated with processes of reactive oxygen species (ROS) signalling, generation of nitric oxide, modulation of ion channel activities and Ca2+ homeostasis, amongst others.

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Polyamines: molecules with regulatory functions in plant abiotic stress tolerance

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

The physiology and biochemistry of polyamines in plants

Petunias (Petunia hybrida cv. ‘Mitchell’) accumulate free proline (Pro) under drought-stress conditions. It is therefore believed that Pro acts as an osmoprotectant in plants subjected to drought conditions. Petunia plants were transformed by D 1 -pyrroline-5-carboxylate synthetase genes (AtP5CS from Arabidopsis thaliana L. or OsP5CS from Oryza sativa L.). The transgenic plants accumulated Pro and their drought tolerance was tested. The Pro content amounted to 0.57–1.01% of the total amino acids in the transgenic plants, or 1.5–2.6 times that in wild-type plants grown under normal conditions. The transgenic plant lines tolerated 14 d of drought stress, which confirms that both P5CS transgenes had full functionality. Exogenous L-Pro treatment caused the plants to accumulate Pro; plants treated with 5 mM L-Pro accumulated up to 18 times more free Pro than untreated plants. Exogenous L-Pro restricted the growth of wild-type petunias more than that of Arabidopsis plants. The capacity for free Pro accumulation might depend on the plant species. The growth of petunia plants was influenced not only by the Pro concentration in the plants, but by the ratio of the Pro content to the total amino acids, because the growth of the transgenic petunia plants appeared normal.

Effects of free proline accumulation in petunias under drought stress

Developing Cell and Tissue Culture Systems for the Improvement of Cereal and Grass Crops

A sensitive (0.01-1 nmol) method has been developed for the analysis of polyamines in higher plant extracts based on high performance liquid chromatography (HPLC) of their benzoyl derivatives (Redmond, Tseng 1979 J Chromatogr 170: 479-481). Putrescine, cadaverine, agmatine, spermidine, spermine, and the less common polyamines nor-spermidine and homospermidine can be completely resolved by reverse phase HPLC, isocratic elution with methanol:water (64%, v/v) through a 5-mum C(18) column, and detection at 254 nm. The method can be directly applied to crude plant extracts, and it is not subject to interference by carbohydrates and phenolics. A good quantitative correlation was found between HPLC analysis of benzoylpolyamines and thin layer chromatography of their dansyl derivatives. With the HPLC method, polyamine titers have been reproducibly estimated for various organs of amaranth, Lemna, oat, pea, Pharbitis, and potato. The analyses correlate well with results of thin layer chromatography determinations.

Analysis of Polyamines in Higher Plants by High Performance Liquid Chromatography

The putrescine content of oat leaf cells and protoplasts increases up to 60-fold within 6 hours of exposure to osmotic stress (0.4 to 0.6 molar sorbitol). Barley, corn, wheat, and wild oat leaves show a similar response. Increased arginine decarboxylase activity parallels the rise in putrescine, whereas ornithine decarboxylase remains unchanged. DL-alpha-Difluoromethylarginine, a specific irreversible inhibitor of arginine decarboxylase, prevents the stress-induced rise in increase in arginine decarboxylase activity and putrescine synthesis, indicating the preferential activation of this pathway.

https://science.sciencemag.org/content/sci/217/4566/1259.full.pdf

Polyamines and Plant Stress: Activation of Putrescine Biosynthesis by Osmotic Shock

Changes in Polyamine Titer in Etiolated Pea Seedlings Following Red Light Treatment

We have developed in vitro culture systems for both "grain" and "vegetable" species of the genus Amaranthus. Leaf discs and hypocotyl segments from 2- to 3-wk-old seedlings of A. hypochondriacus, A. cruentus, and A. tricolor were cultured in B5 and MS media supplemented with 2,4-dichlorophenoxyacetic acid, a-naphthaleneacetic acid, benzyladenine and zeatin in various combinations. Rapidly growing callus and abnormal roots formed on leaf discs of A. hypochondriacus and A. cruentus in the presence of 0. 1-1.0 mg/l 2,4-D. At higher levels (1.010.0 mg/l) of 2,4-D, embryo-like structures arose from the surface and veins of the leaf discs. Shoots formed on hypocotyl-derived callus of both grain species in B5 medium + 0.1 mg/l NAA and 0.1-1.0 mg/l zeatin. Lower ratios of zeatin/NAA stimulated root formation from hypocotyl segments. Viable mesophyll protoplasts were isolated from primary leaves of all three species, with an enzyme solution of 1% Cellulysin and 0.05% Pectolyase Y-23, producing a yield of more than 106 protoplasts/g fresh weight.

In vitro culture of grain and vegetable amaranths (amaranthus spp.)

Publisher Summary This chapter describes protoplasts as vehicles for plant propagation and improvement. To the extent that the multicellular organism may be viewed as a community of interacting individual cells, the behavior of cells in isolation has much to tell about the nature of the organism. The ability of a plant protoplast to synthesize a cell wall, initiate division, and regenerate a complete plant depends on many factors, including its genetic nature, the conditions of growth of the plant used as a protoplast source, the methods of isolation, and conditions used in the culture of the protoplasts themselves. The commercial availability of a number of potent cell wall digesting enzyme preparations has spurred the use of enzymes for protoplast isolation. Callus and suspension cultures, showing rapid growth under controlled aseptic conditions, offer important advantages as a source of protoplasts.

Hector E. Flores

Papers

Analysis of Polyamines in Higher Plants by High Performance Liquid Chromatography

Polyamines and Plant Stress: Activation of Putrescine Biosynthesis by Osmotic Shock

Changes in Polyamine Titer in Etiolated Pea Seedlings Following Red Light Treatment

In vitro culture of grain and vegetable amaranths (amaranthus spp.)

Protoplasts as vehicles for plant propagation and improvement.