IAA and N(6)-benzyladenine inhibit ethylene-regulated expression of ACC oxidase and ACC synthase genes in mungbean hypocotyls.
Regulation of expression of 1-aminocyclopropane-1-carboxylate (ACC) oxidase (VR-ACO1) and ACC synthase (VR-ACS1) genes by ethylene, indole-3-acetic acid (IAA), and N(6)-benzyladenine (BA), was investigated in mungbean hypocotyl tissues. Exogenous ethylene markedly increased transcript level of VR-ACO1 and reduced that of VR-ACS1, whereas aminooxyacetic acid (AOA), an inhibitor of ethylene biosynthesis, decreased the level of VR-ACO1 mRNA and increased that of VR-ACS1, indicating that expression of VR-ACO1 and VR-ACS1 genes are under positive and negative feedback control by ethylene, respectively. However, IAA treatment reduced the level of VR-ACO1 transcripts and increased that of VR-ACS1, although the hormone greatly induced ethylene production. We have demonstrated that, in a system that separates the effect of IAA proper from the effect of IAA-induced ethylene, the amount of IAA-induced ethylene was enough to cause accumulation of VR-ACO1 mRNA and decrease of VR-ACS1 mRNA. We have also shown that the responsiveness of VR-ACO1 and VR-ACS1 to exogenous ethylene was greatly reduced in the presence of IAA. In addition, BA abolished ethylene responsiveness with respect to expression of VR-ACO1 and VR-ACS1. Based on these results, we suggest that IAA and BA inhibit ethylene action, resulting in suppression of VR-ACO1 expression and induction of VR-ACS1 expression.
Kim
J H
JH
Department of Biology, Yonsei University, Seoul 120-749, The Republic of Korea. kimjeon4@msu.edu
Kim
W T
WT
Kang
B G
BG
D000225:Adenine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D000594:Amino Acid Oxidoreductases / Q000235:genetics*; D001593:Benzyl Compounds; D005030:Ethylenes / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D007887:Fabaceae / Q000201:enzymology / Q000235:genetics*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects*; D007210:Indoleacetic Acids / Q000494:pharmacology*; D007701:Kinetin; D008190:Lyases / Q000235:genetics*; D011687:Purines
D001593:Benzyl Compounds; D005030:Ethylenes; D007210:Indoleacetic Acids; D011687:Purines; C030737:indoleacetic acid; C036216:ethylene; D000594:Amino Acid Oxidoreductases; C059460:1-aminocyclopropane-1-carboxylic acid oxidase; D008190:Lyases; C021773:1-aminocyclopropanecarboxylate synthase; D000225:Adenine; C480551:benzylaminopurine; D007701:Kinetin