Growth and stomata development of Arabidopsis hypocotyls are controlled by gibberellins and modulated by ethylene and auxins.
The plant hormones gibberellin (GA), ethylene and auxin can promote hypocotyl elongation of Arabidopsis seedlings grown in the light on a low nutrient medium (LNM). In this study, we used hypocotyl elongation as a system to investigate interactions between GA and ethylene or auxin and analysed their influence on the development of stomata in the hypocotyl. When applied together, GA and ethylene or auxin exerted a synergistic effect on hypocotyl elongation. Stimulated cell elongation is the main cause of hypocotyl elongation. Furthermore, hypocotyls treated with GA plus either ethylene or auxin show an increased endoreduplication. In addition, a small but significant increase in cell number was observed in the cortical cell files of hypocotyls treated with ethylene and GA together. However, studies with transgenic seedlings expressing CycB1::uidA genes revealed that cell division in the hypocotyl occurs only in the epidermis and mainly to form stomata, a process strictly regulated by hormones. Stomata formation in the hypocotyl is induced by the treatment with either GA or ethylene. The effect of GA could be strongly enhanced by the simultaneous addition of ethylene or auxin to the growth medium. Gibberellin is the main signal inducing stomata formation in the hypocotyl. In addition, this signal regulates hypocotyl elongation and is modulated by ethylene and auxin. The implication of these three hormones in relation to cell division and stomata formation is discussed.
Saibo
Nelson J M
NJ
Department of Plant Systems Biology, Flanders Interuniversity Institute for Biotechnology (VIB), Ghent University, K.L. Ledeganckstraat 35, B-9000 Gent, Belgium.
Vriezen
Wim H
WH
Beemster
Gerrit T S
GT
Van Der Straeten
Dominique
D
D017360:Arabidopsis / Q000166:cytology / Q000187:drug effects* / Q000254:growth & development*; D002455:Cell Division / Q000187:drug effects; D005030:Ethylenes / Q000494:pharmacology*; D005875:Gibberellins / Q000494:pharmacology*; D018546:Hypocotyl / Q000166:cytology / Q000187:drug effects* / Q000254:growth & development*; D007210:Indoleacetic Acids / Q000494:pharmacology*; D036226:Seedlings / Q000166:cytology / Q000187:drug effects / Q000254:growth & development; D013997:Time Factors
D005030:Ethylenes; D005875:Gibberellins; D007210:Indoleacetic Acids; C036216:ethylene