Regulation of arginine decarboxylase by spermine in osmotically‐stressed oat leaves

Abstract

Biosynthesis of polyamines in plants is controlled primarily by the enzymes ornithine decarboxylase (EC 4.1.1.17) and arginine decarboxylase (ADC: EC 4.1.1.19), which are responsible for the production of putrescine, and S‐adenosyl‐L‐methionine (SAM) decarboxylase (EC 4.1.1.50) that is necessary for the formation of spermidine and spermine (Spm). Little is known about the metabolic or molecular mechanisms regulating the synthesis of these enzymes. We have studied the regulation of ADC synthesis by Spm in osmotically‐stressed oat (Avena sativa L. ev. Victory) leaves, using a polyclonal antibody to oat ADC and a cDNA clone encoding oat ADC. Treatment with Spm in combination with osmotic stress resulted in increased steady‐state levels of ADC mRNA, yet the levels of ADC activity decreased. This absence of correlation is explained by the fact that Spm inhibits processing of the ADC proenzyme, which results in increased levels of this inactive ADC form and a consequent decrease in the ADC‐processed form. Spermine treatment leads to delayed loss of chlorophyll in dark‐incubated and osmotically‐treated oat leaves. Thus, post‐translational regulation of ADC synthesis by Spm may be important in explaining its anti‐senescence properties.

Cloning and expression of an arginine decarboxylase cDNA from Vitis vinifera L. cell-suspension cultures

“…Malmberg and Cellino (1994) reported that oat ADC is clipped from a 66-kDa precursor polypeptide into 42-and 24-kDa product polypeptides, and this proteolytic cleavage leads to activation of the ADC. Borrell et al (1996) found that spermine inhibits processing of the ADC proenzyme. The presently available molecular tools, such as cDNA clones, the use of transgenic plants over-and under-expressing ADC (Masgrau et al 1997), and analysis of gene promoters fused with reporter genes, will further resolve the endogenous and/or exogenous factors and mechanisms which govern the expression of the ADC gene, the post-translational maturation of ADC protein, and the potential physiological role of polyamines in plants.…”

“…(i) In the absence of spermine, the stress stimulus increased the levels of ADC mRNA; its translation product was an inactive precursor protein, which was cleaved to produce the active enzyme (see also Bell and Malmberg 1990;Malmberg and Cellino 1994). (ii) In the presence of spermine, the stress stimulus also increased the abundance of ADC mRNA, but the posttranslational processing (clipping) of the inactive precursor was inhibited by spermine (Borrell et al 1996). Conversely, Watson and Malmberg (1996), studied the regulation of Arabidopsis thaliana ADC expression by potassium de®ciency, and showed that the 10-fold increase in the enzyme activity and the concomitant 20-fold increase in putrescine levels was not due to changes in mRNA or protein levels.…”

“…Through the use of speci®c, enzymeactivated, irreversible inhibitors of ODC and ADC, it was shown that the rise in putrescine titers, observed in rapidly proliferating plant cells, was due to ODC activity (Cohen et al 1982;Hiatt et al 1986), while the elevated putrescine levels in stressed plant tissues was imputed to ADC Galston 1982, 1984;Slocum and Weinstein 1990). The stress-inducing factors that result in an increase in endogenous putrescine include osmotic stress Galston 1982, 1984;Borrell et al 1996), potassium de®ciency (Richards and Coleman 1952;Watson and Malmberg 1996), other mineral de®ciencies (Basso and Smith 1974), acid and salt stresses (Santerre et al 1990;Chattopadhyay et al 1997;Nam et al 1977), oxidative stress (Tuomainen et al 1996) and NH 4 feeding (Altman and Levin 1993; Triantaphylides et al 1993). Flores and Galston (1984) have shown that de-novo synthesis of enzyme was required for the stress-induced response, which was suspended by translation inhibitors.…”

“…The expression of the gene under stress conditions, however, has not been studied to any extent. Recently, Borrell et al (1996) showed a transient increase in the ADC mRNA levels 1 h after an osmotic stress. The authors proposed a model for regulation of ADC gene expression in their experimental system.…”

Characterization of spermidine and spermine synthases in Lotus japonicus: induction and spatial organization of polyamine biosynthesis in nitrogen fixing nodules

“…In higher plants, polyamines have been implicated in a variety of physiological and developmental processes including, rhizogenesis and development of flowers and fruits (Kakkar et al 2000), root growth , senescence (Pandey et al 2000), somatic and pollen embryogenesis (Bastola and Minocha 1995;Garrido et al 1995). Changes in cellular polyamine content in plant tissues have also been associated with environmental stresses, including mineral deficiency (Watson and Malmberg 1996;Mo and Pua 2002), chilling (Roy and Wu 2001), and salt and osmotic stress (Borrell et al 1996;Legocka and Kluk 2005). Analysis of transgenic plants with altered levels of polyamine biosynthetic enzymes indicated that changes in internal polyamine levels can affect stem elongation, leaf morphology, and root growth (Kumar et al 1996;Capell et al 1998;Malmberg et al 1998;Capell et al 2000).…”