NEWLY DISCOVERED HORMONES

Polyamines (Putrescine, Spermidine, Sperrmine, Cadaverine ) Brassinosteroids Salicylic acid (cut flowers and leafy vegetables) Jasmonates (inhibitors) Systemin Alpha Tocopherols (antioxidants) Fusicoccin (from Fusariutn amygdali) Triacontanol (growth promoter extracted from alfalfa) Turgorins Batasins (causes dormancy in bulbils. Extracted from yam.)

Polyamines

POLYAMINES

Definition Those hormones or compounds which possess

two or more than two amino groups.

These are the polyvalent cation compounds that contain two or more amino groups.

found ubiquitously in all organisms (plants and animals as well as bacteria)

Because of their positive charge they can bind to many macromolecules including DNA, RNA and protein (Kusano et al., 2008)

POLYAMINES The diamine putrescine, the triamine spermidine

and the tetramine spermine are ubiquitous in plant cells (Smith et al, 1979; Bagni and Pistocchi, 1992).

They occur as free cations and as conjugates with phenolic acids and macromolecules (Galston and Sawnhey, 1990).

Their levels increase greatly in response to environmental stresses, most notably under conditions of potassium deficiency, water deficits, salinity stress, anaerobiosis and acid stress (Flores et al, 1989).

Because polyamines are synthesized by amino acid decarboxylation reactions which consume H+, polyamine accumulation may function as part of a homeostatic mechanism to keep intracellular pH at a constant value (Flores et al, 1985).

Polyamines may also play a role in the regulation of DNA replication and cell division, and are implicated in the control of senescence and morphogenesis (Evans and Malmberg, 1989; Galston and Sawnhey, 1990).

It has been proposed that polyamines could be part of an intrinsic signaling network and membrane stabilization (Kusano et al., 2008).

Polyamines also serve as precursors of several classes of alkaloids (Smith et al, 1979; Flores et al, 1989; Hashimoto and Yamada, 1994) which may play important roles in plant defense against herbivores.

Plant-based foods containing polyamines have considerable impact on human health (Lima et al., 2011). Organic foods contain markedly more polyamines than crops grown using conventional procedures

POLYAMINES

Types of polyamines Among the most abundant and

physiologically active polyamines are

Putrescine Spermidine Spermine Cadaverine

COMMON AND UNCOMMON DIAMINES AND POLYAMINES FOUND IN PLANTS

PUTRESCINE

Putrescine (sometimes spelled putrescin or putrescene) is an organic chemical compound NH2(CH2)4NH2 (1,4-diaminobutane or butanediamine) formed by and having the smell of rotting flesh.

It is related to cadaverine; both are produced by the breakdown of amino acids in living and dead organisms. Putrescine and cadaverine were first described by the Berlin physician Ludwig Brieger in 1885.

Putrescine is synthesized in small quantities by healthy living cells by the action of ornithine decarboxylase. The polyamines, of which putrescine is one of the simplest, appear to be growth factors necessary for cell division.

Putrescine

                                             

Chemical name 1,4-Diaminobutane

Other names TetramethylenediamineButane-1,4-diamine

Chemical formula C4H12N2

Molecular mass 88.15 g/mol

Density 0.877 g/cm³

Melting point 27 °C

Boiling point 158-160 °C

PUTRESCINE SYNTHESIS

ARGININE DECARBOXYLASE (ADC)

Arginine decarboxylase (ADC) (a chloroplast localized enzyme (Borrell et al, 1995) is induced by a variety of stresses (most notably potassium deficiency; Watson and Malmberg, 1996) and is thought to be the enzyme primarily responsible for environmental stress-induced putrescine accumulation (Galston and Sawnhey, 1990):

PHYSIOLOGICAL ROLES OF PUTRESCINE Loss of regeneration capacity of rice in long term culture is

associated with massive accumulation of putrescine due to an increase in arginine decarboxylase activity. Difluoromethylarginine, an inhibitor or arginine decarboxylase, restored regeneration capacity to long-term cultures (Bajaj and Rajam, 1996). Spermidine treatment also caused a reduction in putrescine content and arginine decarboxylase activity and restoration of plant regeneration ability (Bajaj and Rajam, 1996). In contrast, putrescine promotes and difluoromethylarginine inhibits somatic embryogenesis in eggplant (Yadav and Rajam, 1998).

The alternative, more direct pathway of synthesis of putresine via ornithine decarboxylation catalyzed by cytosolic ornithine decarboxylase (ODC) [EC 4.1.1.17] is proposed to be of little importance in stress-induced putrescine accumulation, but may be critical in regulation of developmental processes (Galston and Sawhney, 1990; Walden et al, 1997). Increased putrescine biosynthesis catalyzed by ornithine decarboxylase promotes somatic embryogenesis in carrots (Bastola and Minocha, 1995).

Levels of putrescine are higher in a drought tolerant wheat cultivar in comparison to a drought susceptible wheat cultivar. These wheat cultivars also differ for oxidant stress resistance as assayed by resistance to paraquat (Ye et al, 1997). Constitutively elevated levels of Arg decarboxylase and Orn decarboxylase are correlated with paraquat resistance in Conzya bonariensis (Ye et al, 1997). Arg decarboxylase and Orn decarboxylase are differentially regulated in Conzya bonariensis, with only the former detectable in 2 week-old plants. Orn decarboxylase becomes more abundant than Arg decarboxylase in 10 week-old plants (Ye et al, 1997). Exogenously supplied putrescine prevents oxidative damage in paraquat-resistant C. bonariensis (Ye et al, 1997). In part this may be due to inhibition of paraquat uptake by putrescine (Hart et al, 1993). Ye et al (1997) suggest that putrescine and other polyamines could function directly or indirectly as free radical scavengers.

CADAVERINE

Cadaverine is a foul-smelling molecule produced by protein hydrolysis during putrefaction of animal tissue. Cadaverine is a toxic diamine with the formula NH2(CH2)5NH2, which is similar to putrescine. Cadaverine is also known by the names 1,5-pentanediamine and pentamethylenediamine Cadaverine is the decarboxylation product of the amino acid lysine.

However, this diamine is not purely associated with putrefaction. It is also produced in small quantities by living beings. It is partially responsible for the distinctive smell of urine and semen.

Cadaverine

                                                            

Chemical name 1,5-diaminopentane

Other names pentamethylenediaminepentane-1,5-diamine

Chemical formula C5H14N2

Molecular mass 102.18 g/mol

Density 0.870 g/cm³

Melting point 9 °C

Boiling point 178-180 °C

BIOSYNTHESIS OF PUTRESCINE & CADAVERINE

The diamine cadaverine is derived from the amino acid lysine by decarboxylation. Its synthesis is catalyzed by lysine decarboxylase [EC 4.1.1.18]. Cadaverine may play an important role in root development (Gamarnik and Frydman, 1991).

SPERMINE

Spermine is a polyamine involved in cellular metabolism found in all eukaryotic cells. Formed from spermidine, it is found in a wide variety of organisms and tissues and is an essential growth factor in some bacteria. It is found as a polycation at physiological pH. Spermine is associated with nucleic acids and is thought to stabilize helical structure, particularly in viruses.

Crystals of spermine phosphate were first described in 1678, in human semen, by Anton van Leeuwenhoek. The name spermin [sic] was first used by the German chemists Ladenburg and Abel in 1888, and the correct structure of spermine was not finally established until 1926, simultaneously in England (by Dudley, Rosenheim, and Starling) and Germany (by Wrede. et al).

Spermine

                                                     

Systematic name N,N'-bis(3-aminopropyl)butane-1,4-diamine

Other names gerontine, musculamine and neuridine

Chemical formula

C10H26N4

Molecular mass 202.34 g/mol

Density x.xxx g/cm3

Melting point 29°C

Boiling point xx.x °C

SPERMIDINE

Spermidine is a polyamine involved in cellular metabolism that can be used to stimulate the enzyme, T7 RNA polymerase, a type of RNA polymerase.

Inhibits neuronal nitric oxide synthase (nNOS).

Binds and precipitates DNA. May be used for purification of DNA binding

proteins. Stimulates T4 polynucleotide kinase (This

enzyme transfers gamma phosphate from ATP to DNA or RNA) activity.

Spermidine

                                             

Systematic name N-(3-aminopropyl)butane-1,4-diamineN-(3-aminopropyl)-1,4-diaminobutane

Chemical formula C7H19N3

Molecular mass 145.25 g/mol

Properties

Density 0.925 g/mL at 25 °C

Melting point xx.x °C

Boiling point xx.x °C

Refractive index n20/D 1.479(lit.)

Foreign activity DNase, RNase, and protease, none detected

Storage temp. 2-8°C

BIOSYNTHESIS OF SPERMIDINE & SPERMINE

Spermidine, and spermine are synthesized from L-arginine and L-ornithine. Synthesis of spermidine and spermine requires an aminopropyl group derived from SAM, and there may be competition between the ethylene and polyamine biosynthesis pathways when concentrations of SAM are limited. The primary (terminal) amines of polyamines are oxidized by diamine oxidases, the secondary amines by polyamine oxidases.

SPERMIDINE AND SPERMINE SYNTHESIS

The condensation of decarboxylated SAM and putrescine is catalyzed by spermidine synthase (putrescine aminopropyltransferase) [EC 2.5.1.16]. Further condensation of spermidine with decarboxylated SAM, catalyzed by spermine synthase [EC 2.5.1.22], produces the tetramine, spermine (Flores et al, 1989).

METABOLISM OF POLYAMINES

METABOLISM OF POLYAMINES

In addition to serving as a precursor of spermidine and spermine, putrescine has three other metabolic fates; conjugation with hydroxycinnamic acids, metabolism to gamma-aminobutyrate (GABA), and utilization in alkaloid biosynthesis.

(see also discussion of GABA metabolism under Aminotransferase reactions)

GABA can be derived from putrescine (via gamma-aminobutyraldehyde) through the reactions catalyzed by diamine oxidase [EC 1.4.3.6] and gamma-aminobutyraldehyde dehydrogenase (Flores et al, 1989). As noted in the discussion of Quaternary ammonium and tertiary sulfonium compounds, the latter enzyme may be the same as BADH involved in glycinebetaine synthesis (Trossat et al, 1997).

Putrescine serves as precursor of the nicotine and tropane alkaloids (Smith et al, 1979; Flores et al, 1989; Hashimoto and Yamada, 1994), which may play important roles in plant defense against herbivores.

MODE OF ACTION OF POLYAMINES Bonding

In polyamine, amino group contains +ve charge on NH+

3 Which helps to bind with –vely charged phosphate group of DNA and RNA. As a result of this combination, they often increase transcription of DNA and translation of RNA. They enhance or stimulate protein synthesis.

Cell cycle regulation Polyamines cause phosphorylation of proteins,

they are involved in the regulation of cell cycle by controlling the phosphorylation of proteins that take part in cell cycle.

HYDROXYCINNAMIC ACID CONJUGATES OF POLYAMINES

Hydroxycinnamic amide (HCA) conjugates of polyamines accumulate markedly in the floral apex during flower development, and are implicated in the development of competence to flower; certain mutants of tobacco which are deficient in HCAs are unable to flower, and male sterile mutants of maize lack HCA accumulation in anthers (Flores et al, 1989). A novel polyamine conjugate, N4-hexanoylspermidine, has been identified in senescing pea ovaries and petals (Perez-Amador et al, 1996).

PHYSIOLOGICAL FUNCTIONS OF POLYAMINES Membrane Stabilization – Stabilize Membrane Structure and

Function e.g. Thylakoid DNA Stabilization – Interaction with Nucleic acid Spm-DNA

complexes stabilize DNAs against thermal denaturation. Spd also has same effects.

Enzyme Activity – Stimulate enzyme activity e.g. Kinases in animals and and F 1,6 bisphosphate in plant

Cell Division – Enhance Cell Division but polyamines are not involved in Cell Elongation

Buffering of Cellular pH – The reversible protonation of multiple amino groups of PAs, serves as buffer in the cells

Role in Flowering – Floral axis synthesizes large quantities of conjugate PAs de novo

Development of Ovary and Ovule – The development of the ovary and ovules and ovules during maturation seems highly sensitive to PAs.

Embryogenesis – Increases embryogenesis Senescence – At the time of senescence, there is low amount of

PAs. Abiotic Stress Tolerance – Play significant role in abiotic stresses

tolerance like chilling, drought and salinity. Auxin Correlation -Since auxin application increases PAs in plants,

it is proposed that auxins act through PAs to promote growth Tuber formation, Root initiation Fruit ripening