Inhibition of Early Steps in the Gibberellin-Activated Synthesis of α-Amylase

Abstract

Sumnary. Subsequent production of amylase is severely inhibited if barban [4-chloro-2-btutynyl N-(3-chlorophenyl)carbamate] is added to embryo-free half seeds of barley within 4 to 5 hoLurs after gibberellic acid treatment of these seeds. Thirty to 50 mg/L concentrations of barban are effective. Barban inhibition is non-competitive with respect to gibberellic acid. Addition of barban 7 hours or more after gibberellic acid treatment is almost without effect.The delay between gibberellic acid treatment and amylase formation tends to become shorter with more prolonged imbibition periods. Regardless of imbibition period, susceptilbility to barban is lost within 7 hours after gibberellic acid treatment.Other herbicidally active phenylurethanes are also inhibitors, but none are as effective as barbanl. Phenethyl alcohol and 2 arylcarbamates can act as inhibitors.When gi,bberellic acid (GA) is added to embryofree half-seeds of cereals such as barley or wild oats, synthesis of a-amylase by the aleurone layers begins after a lag period (9,16,17). We now report a series of inhibitors which are much more effective when added within a few hours after gilbberellin addition, than when added later.These inhibitors consist primarily of herbicidally active carbamate compounds. One such group is composed of phenvlurethanes, which we will define chemically as Aryl-NH-CO-O-Alkyl compounds, an(l which are noted for severe inhibition of plant cell division. However, a nutmber of carbamates with somewhat' different structures are also effective inhibitors in the barley assay. These non-phenylurethane carbamates will be termed arylcarbamates. Materials and MethodsAll experiments reported here were performed with the Himalaya variety of barley, although we have obtained essentially identical results with the 2-rowed malting variety, Betzes. The first sample of Himalaya seed was supplied by Dr. James Bonner. Most of the experiments were performed with a larger sample generously stupplied by Dr. R. A. Nilan. The seeds were cut transversely and the embryo-containing halves were discarded.Half-seeds were sterilized for 10 minutes in a 1: 33 dilution of a commercial chlorine laundry bleach (Chlorox). They were rinsed with sterile distilled water, and then shaken for 8 hours (exceptions indicated in text) with distilled water containing 5 mg of penicillin and 5 mg of streptomycin per liter (2). Fifteen half-seeds were aseptically transferred into 25 ml Erlenmyer flasks containing 2 ml of antibiotic solution plus various addenda. Sterile technique was followed in transfers and in all subsequent manipulations. Most solutions were sterilized by autoclaving, but heatsensitive materials were filter-sterilized.www.plantphysiol.org on May 11, 2018 -Published by Downloaded from

Contraction of chromosomes and depression of RNA synthesis by isopropyl N-(3-chlorophenyl) carbamate (CIPC) in Vicia faba root tip cells.

“…On the other hand, the production of amylase in GA-treated non-dividing aleurone cells of barley is also inhibited by these herbicides (Yung andMann 1967, Devlin andCunningham 1970). The hypothesis proposed by Mann et al (1967) was to suggest the physiological probability of inhibition of RNA synthesis in the nucleus by carbamate herbicides, perhaps connecting with the observed effects on chromosome contraction.…”

“…The hypothesis proposed by Mann et al (1967) was to suggest the physiological probability of inhibition of RNA synthesis in the nucleus by carbamate herbicides, perhaps connecting with the observed effects on chromosome contraction.…”

Massive Synthesis of Ribonucleic Acid and Cellulase in the Pea Epicotyl in Response to Indoleacetic Acid, With and Without Concurrent Cell Division

“…It is legitimate, therefore, to speculate on the question of where the hormone must act in the sequence of events leading to protein synthesis. Recentlv it has been suggeste(d that plant hormones promote synthesis of specific enzymes by unnmasking the appropriate preformed messenger RNA (22,26) or by charging a particular variety of transfer RNA needed to initiate synthesis (1). Such effects on the process of translation would not necessarily require RNA synthesis.…”

Dormancy of the Barley Grain Is Correlated with Gibberellic Acid Responsiveness of the Isolated Aleurone Layer

“…Trewavas (26,27) proposes that a changing sensitivity of the aleurone cells to gibberellin is as important for the production of a-amylase during germination as the level of gibberellins, because progressively longer imbibition periods of embryoless grains results in a progressive shortening of the lag period of gibberellin-induced a-amylase formation in isolated aleurone layers (29). Furthermore, deembryonation after 1 d of germination leads to subsequent maximum aamylase formation by the half-grains (6), and the osmotic pressure of the grain content determines the acquisition of gibberellin responsiveness because high osmotic pressure inhibits a-amylase synthesis by the aleurone layer (8).…”