Polyamines and Root Formation in Mung Bean Hypocotyl Cuttings

Abstract

ABSTRAC1The incorporation of [l4qsginine and I'4qornithine into various polyamines was studied in mung bean ( Vigna radiata IL.] Wilczek) hypocotyl cuttings with respect to the effect of indole-3-butyric acid on adventitious root formation.Both '4Qujginine and I'4Cornithine are rapidly incorporated into putrescine, spermidine, and spermine, with similar kinetics, during 5-to 24-hour incubation periods. The incorporation of arginine into putrescine is generally higher than that of ornithine. The biosynthesis of putrescine and spermidine from the precursors, in the hypocotyls, is closely related to the pattern of root formation: a first peak at 0 to 24 hours corresponding to the period of root primordia development, and a second peak of putrescine biosynthesis at 48 to 72 hours corresponding to root growth and elongation. Indole-3-butyric acid considerably enhances putrescine biosynthesis in both phases, resulting in an increase of the putrescine/ spermidine ratio.It is concluded that the promotive effect of indole-3-butyric acid on putrescine biosynthesis, from both arginine and ornithine, supports the hypothesis that auxin-induced root formation may require the promotion of polyamine biosynthesis.The biosynthesis and function of naturally occurring PA3 have been studied in detail in mammalian tissues and in procaryotes (4, 7, 19), whereas relatively little is known about PA metabolism in plants. Where the addition of propylamino residues derived from S-adenosyl methionine (1, 4).In recent years, it has been demonstrated that PA. play a significant role in plant responses to hormonal and environmental stimuli, both with respect to growth and active cell division, and to stress and senescence (2,3,6,12). Thus, induction of cell division and growth was studied recently in several plant systems and its close relationship with PA metabolism and biosynthetic enzymes has been demonstrated (14,15,17).In a previous study (10) we suggested that PA are involved in IBA-induced root formation in mung bean cuttings. This conclusion was based on the effect ofexogenous compounds, including PA precursors and some analogs and metabolic inhibitors, and on changes in the titer of endogenous PA. This was recently corroborated by similar data (13) showing that IBA leads to enhanced levels of PA in the hypocotyl where roots are formed (although we could not show that exogenous Spm enhanced root formation). The present investigation was undertaken in order to elucidate the role of PA in auxin-induced root formation by studying the incorporation of L-arginine and L-ornithine into various PA. In the following, we show that these two precursors are rapidly incorporated into Put, Spd, and Spm, with similar kinetics, and that the induction of adventitious roots by IBA is preceded and accompanied by an increase in the incorporation. MATERIALS AND METHODS

Effects of Naphthalene Acetic Acid (NAA) and Indole -3- Butyric Acid (IBA) on In Vitro Rooting of Sugarcane (Saccharum officinarum L.) Micro- Shoots

“…Nevertheless, the main steps in auxin signaling are initial perception of the hormone signal by the receptor protein, the signal transduction cascade, and the final physiological response (root induction). Auxin signal perception by analogy to animal systems each target plant cell is presumed to possess receptors which are able to detect hormonal signals and then to initiate the chain of molecular events leading to the final physiological response [42,43].…”

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

“…In addition, IBA led to enhanced levels of PAs prior to the development of root primordia. An inhibition of root formation was obtained with different inhibitors of Put, Spd, and Spm synthesis such as canavanine, canaline, and methylglyoxal-bis (guanylhydrazone) (14,18,25). Schwartz et al (27) reported an increase in ADC and ODC activities during lateral root formation in Zea mays and showed that ODC was localized mainly in the meristematic root tip zones.…”

“…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.…”

“…1398 Several reports (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.…”

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).…”