Increase in Indoleacetic Acid Oxidase Activity of Winter Wheat by Cold Treatment and Gibberellic Acid

Abstract

The activity of indoleacetic acid oxidase increased 10-fold during 40 days of cold treatment of winter wheat seedlings. Puromycin and 6-methyl purine inhibited indoleacetic acid oxidase development in the cold. Addition of gibberellic acid stimulated indoleacetic acid oxidase development during germination at room temperature and during cold treatment. Amo-1618 inhibited indoleacetic acid oxidase development before and during cold treatment. Indoleacetic acid treatment increased indoleacetic acid oxidase activity during germination at room temperature while no significant effect on activity was observed during cold treatment.The enzymatic oxidation of indoleacetic acid in wheat seedlings has been associated with the peroxidase enzymes (29,35). Galston et al. (8) reported that the IAA oxidase system of peas consisted of a flavoprotein coupled through H202 production to a peroxidase. Wagenknecht and Burris (33) showed that the IAA oxidase in roots of yellow wax beans and in etiolated pea epicotyls was a copper-containing protein. Diphenol oxidase (laccase), a coppercontaining protein, catalyzes the oxidation and decarboxylation of IAA (6).Auxin treatment induces an increase in IAA oxidase activity in lens roots (23,24) and in onion roots (1) and an increase in peroxidase activity in Vicia roots (17). Ockerse, Siegel, and Galston (21) noted that a peroxidase isozyme is repressed by IAA treatment.GA pretreatment causes an increase in peroxidase activity in rice (16) and in IAA oxidation in roots of other plants (7). The IAA oxidase activity increased after GA treatment in corn leaves, and the endogenous IAA level was lower in the treated plant compared at the same time to the control plant (12). KogI and Elevan (19) reported that GA had no effect on the oxidation rate in vitro of IAA with extracts from Piswn, while Pilet (22) reported a protection in vitro by GA on the degradation of IAA with carrot extracts. Other investigators reported no effect of GA on IAA oxidase activity (3,18,31,32 Ag,/ml, respectively) were added to avoid microbial contamination. Seeds were germinated at room temperature (23 C) for 5 days. On the 5th day, the cups were transferred to the cold room (2 C). In cases where seeds were treated with IAA, GA, or Amo-1618, a solution containing the chemical was used to moisten the vermiculite. Solutions of 6-methyl purine (1 X 10-4 M) and puromycin (6.4 X 10-5 M) were added where indicated.Enzyme Extraction. Wheat shoots were homogenized with a mortar and pestle, in 0.05 M sodium phosphate, pH 4.0, containing 0.01 M 2-mercaptoethanol. The homogenate was squeezed through four layers of cheesecloth, and the filtrate was centrifugated at 5,000 g for 5 min. Then, the supernatant solution was centrifuged at 20,000 g for 20 min, and the protein was fractionated by ammonium sulfate precipitation. A 100% saturated ammonium sulfate solution (pH 4.0) was added dropwise to the supernatant solution until the desired concentration was reached.

Decreased panicle-derived indole-3-acetic acid reduces gibberellin A1 level in the uppermost internode, causing panicle enclosure in male sterile rice Zhenshan 97A

“…Plant tissues capable of rapid growth have been found to exhibit low IAA oxidase activity, whereas higher levels of activity were observed in slower growing tissues (Galston and Dalberg, 1954;Bolduc et al, 1970;Darbyshire, 1971). Evidence for an inverse relationship between IAA oxidase activity and endogenous IAA level has been reported (Khan, 2003;Alagarswamy et al, 2004;Parmar and Chanda, 2005).…”

Some physiological and biochemical aspects of chilling injury of grapefruit (Citrus paradisi Macf.) with emphasis on growth regulators /

“…Recent studies have shown levels of IAA oxidase activity may be affected by environmental stress in the form of low temperatures (20) or water stress BA at 2 x 10 M using corn ( Zea mays L. ) . Two days after spraying, plants were chilled at -2°C for 3 hours.…”

The Promotion of Indole-3-acetic Acid Oxidation in Pea Buds by Gibberellic Acid and Treatment

“…Subsequent work with rice seedlings (10) did not support the thesis that interaction between the hormones proceeds via an auxin-sparing system, albeit that IAA oxidase appears to control coleoptile elongation in this tissue. Other investigators have reported no effect of GA on IAA oxidase (3,26), and recently GA has been shown to increase the oxidase activity (2,7). Since the evidence presented here indicates that GA increases IAA oxidase activity, our work does not support a hypothesis based on an auxin-sparing system.…”