Effects of methylglyoxal-bis (guanylhydrazone) and abscisic acid on polyamine metabolism in embryonectomized barley seeds |
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Authors: | Paul P C Lin |
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Institution: | (1) Department of Agronomy, University of Kentucky, 40546-0091 Lexington, KY, USA |
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Abstract: | Incorporation of L-U-14C] arginine or L-U-14C] ornithine into putrescine (Put), spermidine (Spd) and spermine (Spm) in embryonectomized barley seeds (Hordeum vulgare L. cv. Himalaya) was studied following imbition with methylglyoxal-bis (guanylhydrazone) (MGBG) and abscisic acid (ABA). Both radiolabeled amino acids were incorporated into the amines as a result of active polyamine biosynthesis in the seed during imbibition. In the aleurone layer, the Spd and Spn existed mainly in the free form (acid soluble). However about 50% of Put was recovered in conjugated form(s) (acid insoluble). Imbibition with 5 and 10 M ABA for 3 days increased the accumulation of the free form of 14C-Put, probably as a result of inhibition (70%) of 14C-Spd accumulation. The ABA treatment showed no significant effect on levels of the conjugated form of Put and Spd. Imbibition with millimolar concentrations of MGBG resulted in (i) abnormal accumulation of the free form of Put and incorporation of 14C-amino acids into the diamine, (ii) progressive inhibition of the accumulation of the free forms of 14C-Spd and Spm, and (iii) reduction of the 14C incorporation into the conjugated forms of Put and Spd. Uptake of 14C-amino acids was not affected by MGBG treatment. The results indicate that MGBG may inhibit not only the synthesis of Spd and Spm, but the catabolism (e.g. oxidation) of Put in the aleurone layer.This paper is published with the approval of the director of the Kentucky Agricultural Experiment Station. |
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Keywords: | Polyamines MGBG ABA aleurone barley |
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