Polyamines in plants: biosynthesis from arginine, and metabolic, physiological and stress-response roles.

Abstract

Biogenic amines affect a myriad of growth and developmental processes in all organisms, including plants. Therefore, there is continued interest in understanding the biosynthesis and functional roles of polyamines in regulating plant metabolism, physiology and development. The role of polyamines in plant responses to environmental stresses has also elicited considerable interest in recent years. Four major biogenic amines and their derivatives commonly found in plants are putrescine (Put), spermidine (Spd), spermine (Spm) and thermospermine (T-Spm). The biosynthesis of these polyamines derives from arginine (Arg) and/or ornithine (Orn). This chapter's focus is on the Arg pathway. Genes encoding enzymes in the various steps of polyamine biosynthesis from Arg have been identified and characterized from a number of plants. The enzymes catalysing different steps in Arg pathway are: Arg decarboxylase, agmatine iminohydrolase/agmatine deiminase, N-carbamoylputrescine amidase/N-carbamoyl Put amido hydrolase, S-adenosylmethionine decarboxylase, Spd synthase, Spm synthase and T-Spm synthase. Many of these have been purified and studied using heterologous expression systems. Advanced genetics tools and mutants have been used, including production of loss-of-function and gain-of-function plants. Thus far, the studies have provided unequivocal evidence of polyamine role in diverse aspects of plant life. Characterizations of isogenic mutants varying in their endogenous levels of different polyamines have revealed that polyamines are central to important signalling and metabolic pathways, and affect grain filling, senescence, nodulation, root development and fruit ripening, as well as having a role in the abiotic stress responses of plants.

Polyamines and Their Biosynthesis/Catabolism Genes Are Differentially Modulated in Response to Heat Versus Cold Stress in Tomato Leaves (Solanum lycopersicum L.)

“…Polyamines regulate a myriad of developmental and physiological processes including gene expression under both normal and stress conditions [ 28 , 69 ]. Metabolism of these biological amines has been implicated in developing tolerance or survival under harsh environmental conditions, such as heat, cold, drought and salinity stress [ 28 , 36 , 40 , 70 ]. Plant responses to temperature can be divided into four broad categories, including freezing (<−2 °C), chilly/low (−2 °C to 10 °C), optimum growth (15 °C to 25 °C) and high (>35 °C) temperatures.…”

“…The ubiquitous PAs attracted the attention of biologists in the early 1940s as cellular amines that have a role in the biosynthesis of secondary metabolites, particularly related to the diamine putrescine [ 24 ], and later as possible antistress molecules [ 25 , 26 , 27 ]. PAs are now known to be part and parcel of plants’ life cycles ranging from cell division and differentiation, root growth and development, flower development, senescence and programmed cell death (PCD), DNA synthesis, gene transcription, cell wall loosening to fruit maturation and ripening, and plant stress tolerance [ 11 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 ]. The abundant PAs in plants include putrescine (Put), spermidine (Spd) and spermine (Spm), while the less abundant ones include cadaverine, thermospermine, norspermidine and norspermine [ 27 ].…”

“…The abundant PAs in plants include putrescine (Put), spermidine (Spd) and spermine (Spm), while the less abundant ones include cadaverine, thermospermine, norspermidine and norspermine [ 27 ]. PAs as osmo-protectants are considered to protect plants against adverse environmental conditions [ 11 , 28 , 31 , 36 , 37 ], notably drought and salinity in various crops and crop models [ 11 , 31 , 38 , 39 , 40 , 41 ]. These roles for PAs gained further strength from experiments carried out using a variety of agronomic and model plants including tobacco, rice, tomato, Arabidopsis, pear and potato which were engineered to accumulate PAs by overexpressing either S-adenosylmethionine (SAM) decarboxylase (showing tolerance against salt, osmotic and heat stresses) [ 31 , 42 ], or Spd synthase (showing tolerance against drought, salt and oxidative stresses) [ 31 , 43 , 44 , 45 , 46 , 47 ].…”

“…Plants utilize both ornithine and arginine biosynthesis pathways for PAs except for Arabidopsis, in which an ornithine decarboxylase ( ODC) encoding gene(s) is yet to be found [ 36 ]. Arg is converted to Put by Arginine decarboxylase (ADC; EC 4.1.1.19) while Ornithine decarboxylase (ODC; EC 4.1.1.7) converts Orn to Put [ 36 , 48 ]. In addition, the activity of arginase (ARG; EC 3.5.3.1), which catalyzes Arg to ornithine, balances both pathways.…”

Citrus Polyamines: Structure, Biosynthesis, and Physiological Functions

“…The biosynthetic pathway of PAs has been extensively studied in all the kingdoms of living organisms, from Bacteria to Archaea and Eukaryotes [29,[63][64][65][66][67][68][69][70]. However, our knowledge about Once putrescine is produced, it is then converted into the tri-amine spermidine by spermidine synthase (SPDS; EC 2.5.1.16), with the addition of an aminopropyl moiety donated by decarboxylated S-adenosylmethionine (dcSAM).…”