Polyamines, Hydroxycinnamoylputrescines, and Root Formation in Leaf Explants of Tobacco Cultivated in Vitro

Abstract

In vitro formation of roots is obtained directly, without intermediate growth of callus, from foliar explants of a tobacco (Nicotiana tabacum) plant cultured on Murashige and Skoog medium containing IAA. Auxin-induced root formation was accompanied by significant changes in hydroxycinnamoylputrescine levels. Increasing levels were found in leaf explants during the first 14 days in culture; this was followed by a sharp decline after 20 days. Early changes in putrescine conjugates were detected in leaf explants before the visible appearance of roots. An early and transitory accumulation of hydroxycinnamoylputrescines was observed in the roots. Free polyamines (putrescine, spermidine, and spermine) in leaf explants and roots were always at a low level and only small changes in their concentrations were observed, a-DL-difluoromethylarginine and a-DL-difluoromethylomithine, specific, irreversible inhibitors of arginine decarboxylase and ornithine decarboxylase, respectively, inhibited putrescine accumulation and root initiation and reduced the fresh and dry weights of leaf explants. These effects were reversed by free putrescine or hydroxycinnamoylputrescines. The results reported here suggest that hydroxycinnamoylputrescines are associated with root formation. The relationship among free polyamines, hydroxycinnamoylputrescines, cell division, and root formation is discussed. (10,14,25) suggest that polyamines are involved in auxin-induced root formation, although their specific role has yet to be elucidated in order to establish a causal relationship.Amides formed between hydroxycinnamic acids and amines are widely distributed in the plant kingdom (9,20,21,28). They are detected in high amounts in flowering parts ofvarious plants and have been linked to the process offlower formation (for reviews, see refs. 20 and 31). Other factors leading to an increase in conjugated polyamines are fungal and viral infections, (for reviews see refs. 20 and 31). Recent results (8,22) report that a change in morphology or growth of tobacco leaf explants in vitro is accompanied by changes in putrescine levels, and the largest changes occur in conjugated putrescine content specifically.Are polyamines and conjugated polyamines esssential for root formation, or are they simply secondary by-products of a growth response? One way to approach this question is by utilizing specific inhibitors of polyamine synthesis and then examining the physiological properties of tissues.Previous reports have shown that in tobacco plants putrescine is synthesized from arginine (by ADC' via agmatine) and ornithine (by ODC).This study reports results of DFMA, a specific enzymeactivated ADC inhibitor, and DFMO, a specific enzymeactivated ODC inhibitor, on organogenesis, growth, free polyamine, and conjugated polyamine (hydroxycinnamoylputrescine) levels of tobacco leaf explants cultivated in vitro in a medium that induces root formation. MATERIALS AND METHODS Biological Material and Growth ConditionsNicotiana tabacum var Xanthi n.c. was utilized in ...

Polyamine synthesis and accumulation in the hypersensitive response to TMV in Nicotiana tabacum

“…The increasing activity of ODC, which is thought to be responsible for supplying free putrescine needed for conjugate synthesis (Burtin et al, 1990;Biondi et al, 1993), does not correlate with the decrease in free and conjugated putrescine observed on day 5. This could possibly be due to an increase in oxidative activity.…”

“…This supports been shown that the Nicotiana hybrid RMB7, which the conclusion that HCAs are effective in controlling has lost its capacity to flower, does not synthesize the spread of the virus. It is notable that conjugated detectable HCAs at any stage during development, polyamines are also synthesized in tobacco plants in When infected with TMV, it initially produces vitro during the regeneration of roots, shoots or necrotic lesions as in a typical HR, but eventually the flowers (Burtin et aL, 1990;Bagni et aL, 1993). virus spreads systemically, the plant dies, and no Changes in free or conjugated polyamines, howHCAs are produced (Martin & Martin-Tanguy, ever, do not appear to be specific to biotic stress.…”

Polyamines in grapevine microcuttings cultivated in vitro. Effects of amines and inhibitors of polyamine biosynthesis on polyamine levels and microcutting growth and development

“…amines covalently linked to cinnamic acids) and aromatic amines also occur [20] . These conjugates are associated with major developmental and physiological processes : (A) root and callus formation [4,5] (B) flowering and seed fruit development [6,16,20], and (C) the hyper sensitive response to viral or fungal infection [20] .…”

“…The functions of polyamines in cell division and morphogenic processes in plant systems have been studied in experiments designed to (A) search for correlation between polyamine levels and cell division or morphogenic processes or (B) to study the effects of exogenous polyamines on cell division or (C) to examine the effects of inhibitors of polyamine biosynthesis (with and without exogenous polyamines) on morphogenic processes [3,4,5,6] . Translocation of polyamines was reported in tobacco plants [6] .…”

Polyamines are involved in the gynogenesis process in onion

“…Several auxininduced organogenesis processes were reported to require the promotion of PA biosynthesis, e.g. root formation in mung bean hypocotyl cuttings (Friedman et al 1985) or in leaf explants of tobacco (Burtin et al 1990), growth of immature cotyledons of Prunus avium (Garin et al 1995) and adventitious organogenesis (Scoccianti et al 2000) or somatic embryogenesis (Yadav and Rajam 1997) from eggplant explants. The effect of auxin was explained as an inhibition of arginine decarboxylase (ADC) activity in carrot cell culture (Fienberg et al 1984) or as a stimulation in pea ovaries (Pérez-Amador and Carbonell 1995) or in BAP-treated Cucumis sativus cotyledons (Suresh et al 1978).…”