Concentration of Indole-3-acetic Acid and Its Derivatives in Plants

Abstract

Seeds of oat, coconut, soybean, sunflower, rice, millet, kidney bean, buckwheat, wheat, and corn and vegetative tissue of oit, pea, and corn were assayed for free indole-3-acetic acid (IAA), esterifled IAA, and peptidyl IAA. Three condusions were drwn: (a) al plat tissues examined contained most of their IAA as derivatives, either esterified or as a peptide; (b) the cereal grins examined contained mainly ester IAA; (c) the legume seeds examined contained mainly peptidyl IAA. Errors in analysis of free and bound IAA are dicsed.Previous studies from this laboratory have described the isolation and characterization of esters of IAA and myo-inositol, and of IAA and myo-inositol glycosides (cf. 19, 28) from Zea mays. The isolation of the 2-0, 4-0, and 6-0 esters of IAA and glucose (7) and esters having 2 or 3 mol of IAA/mol of inositol (9) have also been described. In (3,21) and an abstract of some of these data has appeared (25). This is the first attempt to assay simultaneously for free, ester and peptidyl IAA in a variety of plants.The validity of the isotope dilution method was established for IAA from Zea and Avena by demonstrating identity of the IAA by mass spectrometry and agreement in quantity when estimated by spectral, colorimetric, and gas chromatographic methods (3). Isotope dilution analysis of IAA has been accomplished earlier by Hamilton et al. (14) and by Belli et al. (4 Sunflower seed (Helianthus annuus), millet (Panicum miliaceum), buckwheat (Fagopyrum esculentum), and wheat (Triticum aestivum) were from a local health food store and gave 84, 23, 99, and 98% germination, respectively. Avena and Zea seed were as previously described (3, 21) and peas were from Vaughan's Seed Co., Ovid, Mich. Yeast (Saccharomyces cerevisiae) was a bakers' yeast from Anheuser Busch.Extraction. Vegetative tissue was extracted by homogenization in 70% acetone as previously described (3). The "4C-IAA and unlabeled, protective, indole-3-butyric acid were added immediately after homogenization. Yeast was treated as vegetative tissue except that 1,000 g were suspended in 1,700 ml of acetone to yield a final acetone concentration of 63%. Seeds were ground to a coarse powder in a hammer mill and samples of 300 g extracted for 10 hr in 2 liters of 70% acetone to which the "4C-IAA and indole-3-butyric acid had been added (3). The acetone extract was collected by filtration and the residue resuspended in 2 liters of 70% acetone and reextracted for 12 additional hr. Following filtration, the extracts were combined and reduced in volume (3).Hydrolysis and Extraction of IAA. Free IAA was extracted into ether from the acidified concentrated extract as described (3). Ester IAA was defined as IAA which was liberated by hydrolysis for 1 hr in 1 N NaOH at 22 to 25 C. Following hydrolysis the mixture was acidified and IAA plus hydrolyzed ester IAA were extracted into ether as described (3). Peptidic IAA was defined as IAA liberated during 3 hr of hydrolysis in 7 N NaOH at 100 C. For hydrolysis of peptidic IAA, the 70% acetone ...

Seed Effects on Gibberellin Metabolism in Pea Pericarp

“…We have previously shown that pericarp tissue metabolizes [2HJGA53 to [2HJGA20 and f2H]GA1, but only when the pericarp is intact and attached to the plant (13). This report describes the first evidence that supports the hypothesis that GA biosynthesis from 1 Supported in part by the National Science Foundation ( GA12 occurs in the pericarp and is regulated remotely by the presence of seeds.…”

A Novel Auxin Conjugate Hydrolase from Wheat with Substrate Specificity for Longer Side-Chain Auxin Amide Conjugates

“…IAA-Ala has been detected in Picea abies Karst (Ö stin et al, 1992). Additionally, IAA-Ala, IAA-Asp, IAA-Leu, and IAA-Glu have been detected in Arabidopsis L. Heynh (Tam et al, 2000;Kowalczyk and Sandberg, 2001), although recent data suggest that IAA peptides may account for the majority of amide conjugates in this and other plant species (Walz et al, 2002;Park et al, 2003).Common IAA-ester conjugates include IAAmyoinositol glycosides, IAA-myoinositol, and IAAGlc (Bandurski et al, 1969;Kopcewicz et al, 1974;Bandurski and Schulze, 1977;Domagalski et al, 1987). These ester conjugates have been identified in many species over the last 60 years (Bandurski et al, 1969;Slovin et al, 1999).…”

Metabolism of Auxin in Tomato Fruit Tissue

“…The two major peaks were collected separately, and the identity of the metabolites corresponding to these peaks was further investigated by subjecting them either to hydrolysis by 1 N NaOH at room temperature for detecting ester conjugates or 7 N NaOH at 1000C for detecting amide-linked conjugates (2). The indolic moiety of the two metabolites was released only by the strong base hydrolysis.…”