Synthesen einiger β‐Indolacetyl‐aminosäuren und ‐peptide

The auxin activities of a number of indoleacetylamino acid conjugates have been determined in three test systems: growth of tomato hypocotyl explants (Lycopersicon esculentum Mill. cv. Marglobe); growth of tobacco callus cultures (Nicotiana tabacum L. cv. Wisconsin 38); and ethylene production from pea stems (Pisum sativum L. cv. Alaska). The activities of the conjugates differ greatly depending on the amino acid moiety. Indoleacetyl-L-alanine supports rapid callus growth from the tomato hypocotyls while inhibiting growth of shoots and roots. Indoleacetylglycine behaves in a similar manner but is somewhat less effective in supporting callus growth and in inhibiting shoot formation. The other amino acid conjugates tested (valine, leucine, aspartic acid, threonine, methionine, phenylalanine, and proline) support shoot formation without supporting root formation or much callus growth. The tobacco callus system, which forms abundant shoots in the presence or absence of free indoleacetic acid, produces only rapid undifferentiated growth in the presence of indoleacetyl-L-alanine and indoleacetylglycine. The other conjugates inhibit shoot formation weakly if at all. Most of the conjugates induce sustained ethylene production from the pea stems but at rates well below the initial rates observed with free indoleacetic acid. Many, but not all of the effects of conjugates such as indoleacetyl-L-alanine can be mimicked by frequent renewals of the supply of free indoleacetic acid.

“…Most of the amino acid conjugates were synthesized by the mixed anhydride method ofWeiland and Horlein (29). The synthesis of IAA-L-alanine is described as an example.…”

Section: Methodsmentioning

confidence: 99%

Biological Activities of Indoleacetylamino Acids and Their Use as Auxins in Tissue Culture

Hangarter¹,

Peterson²,

Good³

1980

“…Radioactive IAAla (10 mCi/mmol) was synthesized by the mixed anhydride procedure (25), as modified by Hangarter et al (16) (12), except that an ether extraction was employed instead of chloroform. The resulting extract was separated into three samples, two of which were subjected to weak or strong base hydrolysis (6), in order to release free IAA from esteric or amide IAA conjugates, respectively.…”

mentioning

confidence: 99%

Carbohydrates Stimulate Ethylene Production in Tobacco Leaf Discs

Meir¹,

Philosoph‐Hadas²,

Epstein³

et al. 1985

Various natrlly occurrg carbohydrates, applied at a concentration range of I to 100 m, lated ethyene producto for severl days in indoleacetic acid (IAA)-treated or untreated tobacco (Nicotiana tabacam L cv 'Xanthi') laf discs. The lag period for this sugr-stimulated ethylene prodution was 8 to 12 hours after excision in the untreated leaf discs, but less than 2 hours in the IAA-treated ones. Among the tested carbohydrates, 12 were foud to increase synergistically ethylene production, with D-galatose, sucrose, and lactose being the most active; annitol and L-ghose had o effec. The extent and duration of the increased ethylene production was dependent upon the type of sur applied, the tissu's age, and the existence of both exogeonos IAA and sar in the medium. Sucrose appeared to elicit a continuous IAA effect for 48 hours, as expressed by increased ethylene production, even when IAA was removed from the medium after a 4-hour pulse. Sucrose stimulted both the uptake and decarboxylation of [1-'4CIAA, as well as the hydrolysis of the esteric and amide IAA conjuptes formed in the tissue after appication of free IAA. This gradual hydrolysis was accompanied by a further accumulation of a third IAA metabolite. Moreover, synthetic indole-3-acetyl-L-alanine increased ethylene production mainly with sucrose, and this effect was accompanied by its increased decarboxylation and turnover pattern suggesting that release of free IAA was involved. An esteric IAA conjugate, tentatively identified by GC retention time was found to be the major component (84%) of the naturally occwuing IAA conjugates in tobacco leaves. Accordingly the sucrosestimuted ethylene production in tobacco leaves can be ascribed maily to the sucrose-stimulated hydrolysis of the esteric IAA conjugate.carbohydrates tested could elicit a stimulating effect in either of those systems, nor in pea epicotyls (8), and it was therefore suggested that the increased ethylene production in these tissues might be related to the toxicity of galactose (I 1) or stress effect of mannitol (21).Our recent study (3) established that sucrose could stimulate IAA-induced ethylene production in a synergistic action. This occurred only in tissues which were responsive to IAA with respect to ethylene production.A possible involvement of IAA in the sugar-stimulated ethylene production could be related to ACC2 formation from SAM, which is the rate-limiting step in ethylene biosynthesis and was found to be stimulated both by IAA (26) Intact leaves as well as leafdiscs of tobacco, incubated in plain water or buffer, produced very small amounts of ethylene (2). When 2% sucrose was added to tobacco leaf discs as a medium constituent, a remarkable increase in ethylene production, which lasted for several days, was observed. This occurred both in IAAtreated and untreated leaf discs, with the increase being much more pronounced in the former (3). A carbohydrate-stimulated ethylene production has been described so far in mung bean hypocotyls treated with D-galactose (I 1) and recent...

“…These possibilities were tested by studying the metabolism of IAA conjugates synthesized from MATERIALS AND METHODS Synthesis of IAA Conjugates. Radioactive IAA-L-alanine and IAA-glycine were synthesized by the mixed anhydride procedure of Wieland and Horlein (12), with the modifications reported by Hangarter et al (7). The unlabeled IAA conjugates were also synthesized by the mixed anhydride method (7).…”

mentioning

confidence: 99%

Evidence That IAA Conjugates Are Slow-Release Sources of Free IAA in Plant Tissues

Hangarter¹,

Good²

1981

119

Evidence that indoleacetic acid (IAA) 'Fingerprints' of Auxin Metabolites. Pea seeds (Pisum sativum L. cv. Alaska) were sterilized by soaking for 15 min in 0.5% NaOCl solution containing 0.01% sodium laurylsulfate. The seeds were then rinsed several times in sterile distilled H20 and germinated in the dark on water-agar (0.6%). Six to 7 days after planting, the epicotyls were excised aseptically, cutting them just below the plumular hook and 2 cm above the seed. The epicotyls were then cut into 1-cm segments. Approximately 10 g of segments were transferred into 125-ml flasks containing 25 ml of autoclaved Murashige and Skoog (9) nutrient medium and 1.0 ,Ci of [1-14CJ IAA or [l-14C]IAA-amino acid (10 mCi/mmol). The tissue was incubated in the dark at room temperature, with shaking for 72 h. The medium was filtered off on a Buchner funnel, and the tissue was rinsed several times with distilled H20.The treated tissues were then placed in beakers with 95% ethanol (2 ml/g). Unlabeled IAA and appropriate IAA conjugates were added at this time to provide carrier and chemically detectable internal chromatographic standards. The tissues were boiled for 3 min in the ethanol, then homogenized with a mortar and pestle. The homogenate was filtered with suction on a Buchner funnel, and the residue was rinsed several times with 80% ethanol. The combined ethanol fractions were concentrated to a viscous residue by distillation of the solvent at reduced pressure and then resuspended in 2-propanol:water (1:1, v/v). This solution was passed over a DEAE-Sephadex-acetate column (1 x 10 cm). The column was washed with 25 ml 2-propanol:water (1:1, v/v). The column was then eluted with a linear gradient of 0 to 3% H3PO4 in 2-propanol:water (1:1, v/v). The fraction containing the acidic indoles (eluting between 20 and 25 ml) was collected, and the propanol was evaporated at reduced pressure. The remaining aqueous fraction was immediately extracted three times with 25 ml diethyl ether. The ether fractions were pooled and washed once with 2 ml water. The ether fraction was then evaporated to dryness at reduced pressure and resuspended in 0.5 ml 95% ethanol. This alcohol solution, containing the acidic, ether-soluble metabolites was used for TLC.