Auxin and brassinosteroid differentially regulate the expression of three members of the 1-aminocyclopropane-1-carboxylate synthase gene family in mung bean (Vigna radiata L.).
Indole-3-acetic acid (IAA) markedly increased ethylene production by inducing the expression of three 1aminocyclopropane-1-carboxylate (ACC) synthase cDNAs (pVR-ACS1, pVR-ACS6 and pVR-ACS7) in mung bean hypocotyls. Results from nuclear run-on transcription assay and RNA gel blot studies revealed that all three genes were transcriptionally active displaying unique patterns of induction by IAA and various hormones in etiolated hypocotyls. Particularly, 24-epibrassinolide (BR), an active brassinosteroid, specifically enhanced the expression of VR-ACS7 by a distinct temporal induction mechanism compared to that of IAA. In addition, BR synergistically increased the IAA-induced VR-ACS6 and VR-ACS7 transcript levels, while it effectively abolished both the IAA- and kinetin-induced accumulation of VR-ACS1 mRNA. In light-grown plants, VR-ACS1 was induced by IAA in roots, and VR-ACS6 in epicotyls. IAA- and BR-treatments were not able to increase the VR-ACS7 transcript in the light-grown tissues. These results indicate that the expression of ACC synthase multigene family is regulated by complex hormonal and developmental networks in a gene- and tissue-specific manner in mung bean plants. The VR-ACS7 gene was isolated, and chimeric fusion between the 2.4 kb 5'-upstream region and the beta-glucuronidase (GUS) reporter gene was constructed and introduced into Nicotiana tabacum. Analysis of transgenic tobacco plants revealed the VR-ACS7 promoter-driven GUS activity at a highly localized region of the hypocotyl-root junction of control seedlings, while a marked induction of GUS activity was detected only in the hypocotyl region of the IAA-treated transgenic seedlings where rapid cell elongation occurs. Although there was a modest synergistic effect of BR on the IAA-induced GUS activity, BR alone failed to increase the GUS activity, suggesting that induction of VR-ACS7 occurs via separate signaling pathways in response to IAA and BR. A scheme of the multiple regulatory pathways for the expression of ACC synthase multigene family by auxin and BR is presented.
Yi
H C
HC
Department of Biology, College of Science, Yonsei University, Seoul, Korea.
Joo
S
S
Nam
K H
KH
Lee
J S
JS
Kang
B G
BG
Kim
W T
WT
D060406:Brassinosteroids; D002777:Cholestanols / Q000494:pharmacology*; D018744:DNA, Plant / Q000235:genetics / Q000302:isolation & purification; D005030:Ethylenes / Q000096:biosynthesis; D007887:Fabaceae / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant / Q000235:genetics; D005966:Glucuronidase / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D007210:Indoleacetic Acids / Q000494:pharmacology*; D007527:Isoenzymes / Q000235:genetics; D008190:Lyases / Q000235:genetics*; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics*; D010937:Plant Growth Regulators / Q000494:pharmacology; D030821:Plants, Genetically Modified; D010946:Plants, Medicinal; D010947:Plants, Toxic; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D012680:Sensitivity and Specificity; D013260:Steroids, Heterocyclic / Q000494:pharmacology*; D014018:Tissue Distribution; D014026:Nicotiana / Q000187:drug effects / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects
D060406:Brassinosteroids; D002777:Cholestanols; D018744:DNA, Plant; D005030:Ethylenes; D007210:Indoleacetic Acids; D007527:Isoenzymes; D010937:Plant Growth Regulators; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D013260:Steroids, Heterocyclic; C036216:ethylene; D005966:Glucuronidase; D008190:Lyases; C021773:1-aminocyclopropanecarboxylate synthase; C023623:brassinolide