Polyamine Metabolism and Osmotic Stress

Abstract

Cereal leaves subjected to the osmotica routinely used for protoplast isolation show a rapid increase in arginine decarboxylase activity, a massive accumulation of putrescine, and slow conversion of putrescine to the higher polyamines, spermidine, and spermine (HE Flores, AW Galston 1984 Plant Physiol 75: 102). Mesophyll protoplasts from these leaves, which have a high putrescine:polyamine ratio, do not undergo sustained division. By contrast, in Nicotiana, Capsicum, Datura, Trigonelia, and Vigna, dicot genera that readily regenerate plants from mesophyll protoplasts, the response of leaves to osmotic stress is opposite to that in cereals. Putrescine titer as well as arginine and ornithine decarboxylase activities decline in these osmotically stressed dicot leaves, while spermidine and spermine titers increase. Thus, the putrescine:polyamine ratio in Vigna protoplasts, which divide readily, is 4-fold lower than in oat protoplasts, which divide poorly. We suggest that this differing response of polyamine metabolism to osmotic stress may account in part for the failure of cereal mesophyll protoplasts to develop readily in vitro.Regeneration of entire plants from mesophyll protoplasts of Gramineae is still difficult (4), with only one authenticated report in the literature (21). By contrast, in the Solanaceae (3) or Leguminosae (11,13,14), many species of plants have been successfully regenerated from protoplasts.A decade ago, when we observed that PAs2 could retard the rapid senescence and lysis of oat protoplasts (1, 8), we initiated a detailed study of the role of PAs in plant cells (16). We were surprised to find that the Put content of mesophyll protoplasts of oat is 5 to 10 times higher than that of the leaves from which they were derived. Later work showed that cereal leaves subjected to 0.4 to 0.6 M sorbitol exhibit a rapid increase in ADC activity, a massive accumulation of Put, and very slow changes in the higher PAs, Spd, and Spm (5, 6), which are normally formed from Put.In the present investigation, we have studied the effect of osmotic stress in tobacco and other species that can be readily regenerated from protoplasts. The results indicate that tobacco response differs from that observed previously for cereals during osmotic stress (18 by N:P:K: analysis, Hydroponics Chemical Co., Copley, OH) and grown in a controlled chamber under a 16-h light/8-h dark photoperiod (9:1 energy mixture of fluorescent and incandescent light at 17.6 Wm-2) at 240 C.Osmotic Treatment of the Excised Leaves. Median leaves from about 2-month-old tobacco, pepper and Datura or about 1-month-old Trigonella or moth bean or the first leaf of 8-d-old oat seedlings were excised. The lower epidermis was peeled off, and leaf discs (2 cm diameter) or segments (5 cm length) were floated in the dark, unless otherwise indicated, at room temperature over 10 ml 1 mM K-phosphate (pH 5.8) contained in a 100 x 15 mm Petri dish, in the absence (control) or presence of osmotica (0.6 M sorbitol) for various incubation times.Preparation...

Early studies on the effect of peptide growth factor phytosulfokine-α on Brassica oleracea var. capitata L. protoplasts

“…Protoplast viability of all tested accessions on Day 1 after isolation was high (approximately 80-90%), and in that time the effect of PSK-α on protoplast viability was less obvious; however, the differences were visible later, on fifth day of culture, when viability decreased in all tested accessions. Decrease in protoplast viability over the first days of culture was reported previously [32,34] and might be associated with the damage in plasma membranes as a result of enzyme digestion and purification, osmotic stress, or oxidative stress during isolation and culture establishment [13,42]. Here, on Day 5, protoplast-derived cells of majority of tested accessions were more viable when cultured in the medium with PSK-α in comparison with the control.…”

Polyamines Improve K+/Na+ Homeostasis in Barley Seedlings by Regulating Root Ion Channel Activities

“…K 1 deficiency may be the first reported stress condition that resulted in an increase in putrescine level in barley (Hordeum vulgare; Richard and Coleman, 1952). In addition, osmotic shock (Tiburcio et al, 1986), drought (Erdei et al, 1996), chilling (Shen et al, 2000), and air pollution (Wellburn and Wellburn, 1996) also could increase polyamine levels as well. Regarding salt stress, polyamine levels were increased in several crop species including rice (Oryza sativa), mung bean (Vigna radiata), maize (Zea mays), barley, and sorghum (Sorghum bicolor; Friedman et al, 1989;Krishnamurthy and Bhagwat, 1989;Rodriguez-Kessler et al, 2006).…”

Arginine Decarboxylase Is Localized in Chloroplasts

“…ADC and ODC activities were determined as described elsewhere (Tiburcio et al, 1986). No significant release of CO, was observed in enzyme extracts preincubated with DFMA or DFMO.…”