Hormonal cross-talk between auxin and ethylene differentially regulates the expression of two members of the 1-aminocyclopropane-1-carboxylate oxidase gene family in rice (Oryza sativa L.).
Two cDNA clones, pOS-ACO2 and pOS-ACO3, encoding 1-aminocyclopropane-1-carboxylate (ACC) oxidase were isolated from rice seedling cDNA library. pOS-ACO3 is a 1,299 bp full-length clone encoding 321 amino acids (Mr=35.9 kDa), while pOS-ACO2 is 1,072 bp long and is a partial cDNA clone encoding 314 amino acids. These two deduced amino acid sequences share 70% identity, and display a high degree of sequence identity (72-92%) with previously isolated pOS-ACO1 of deepwater rice. The chromosomal location studies show that OS-ACO2 is positioned on the long arm of chromosome 9, while OS-ACO3 on the long arm of chromosome 2 of rice genome. A marked increase in the level of OS-ACO2 transcript was observed in IAA-treated etiolated rice seedlings, whereas the OS-ACO3 mRNA was greatly accumulated by ethylene treatment. Results of ethylene inhibitor studies indicated that auxin promotion of the OS-ACO2 transcription was not mediated through the action of auxin-induced ethylene. Thus, it appears that there are two groups of ACC oxidase transcripts in rice plants, either auxin-induced or ethylene-induced. The auxin-induced OS-ACO2 expression was partially inhibited by ethylene, while ethylene induction of OS-ACO3 transcription was completely blocked by auxin. These results indicate that the expression of ACC oxidase genes is regulated by complex hormonal networks in a gene specific manner in rice seedlings. Okadaic acid, a potent inhibitor of protein phosphatase, effectively suppressed the IAA induction of OS-ACO2 expression, suggesting that protein dephosphorylation plays a role in the induction of ACC oxidase by auxin. A scheme of the multiple regulatory pathways for the expression of ACC oxidase gene family by auxin, ethylene and protein phosphatase is presented.
Chae
H S
HS
Department of Biology, College of Science, Yonsei University, Seoul, Korea.
Cho
Y G
YG
Park
M Y
MY
Lee
M C
MC
Eun
M Y
MY
Kang
B G
BG
Kim
W T
WT
D000594:Amino Acid Oxidoreductases / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D002874:Chromosome Mapping; D005030:Ethylenes / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids / Q000378:metabolism*; D008969:Molecular Sequence Data; D012275:Oryza / Q000235:genetics / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D018749:RNA, Plant / Q000032:analysis
D005030:Ethylenes; D007210:Indoleacetic Acids; D018749:RNA, Plant; C036216:ethylene; D000594:Amino Acid Oxidoreductases; C059460:1-aminocyclopropane-1-carboxylic acid oxidase