Plant Physiol.
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH
QUICK SEARCH:   [advanced]


     

Plant Physiology Preview
Published on April 30, 2004; 10.1104/pp.104.038935

This Article
Right arrow Full Text (Plant Physiology Preview (PDF))
Right arrow All Versions of this Article:
135/1/221    most recent
pp.104.038935v1
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via CrossRef
Right arrow Citing Articles via Web of Science (11)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Israelsson, M.
Right arrow Articles by Moritz, T.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Israelsson, M.
Right arrow Articles by Moritz, T.
Agricola
Right arrow Articles by Israelsson, M.
Right arrow Articles by Moritz, T.

Received January 12, 2004
Returned for revision February 25, 2004
Accepted March 2, 2004

Cloning and Overproduction of Gibberellin 3-Oxidase in Hybrid Aspen Trees. Effects on Gibberellin Homeostasis and Development

Maria Israelsson , Ewa Mellerowicz , Makiko Chono , Jonas Gullberg , and Thomas Moritz *

Umea Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE-901 83 Umea, Sweden

* Corresponding author; email: thomas.moritz{at}genfys.slu.se.

To broaden our understanding of gibberellin (GA) biosynthesis and the mechanism whereby GA homeostasis is maintained in plants, we have investigated the degree to which the enzyme GA 3-oxidase (GA3ox) limits the formation of bioactive GAs in elongating shoots of hybrid aspen (Populus tremula x Populus tremuloides). We describe the cloning of a hybrid aspen GA3ox and its functional characterization, which confirmed that it has 3{beta}-hydroxylation activity and more efficiently converts GA9 to GA4 than GA20 to GA1. To complement previous studies, in which transgenic GA 20-oxidase (GA20ox) overexpressers were found to produce 20-fold higher bioactive GA levels and subsequently grew faster than wild-type plants, we overexpressed an Arabidopsis GA3ox in hybrid aspen. The generated GA3ox overexpresser lines had increased 3{beta}-hydroxylation activity but exhibited no major changes in morphology. The nearly unaltered growth pattern was associated with relatively small changes in GA1 and GA4 levels, although tissue-dependent differences were observed. The absence of increases in bioactive GA levels did not appear to be due to feedback or feed-forward regulation of dioxygenase transcripts, according to semiquantitative reverse transcription polymerase chain reaction analysis of PttGA20ox1, PttGA3ox1, and two putative PttGA2ox genes. We conclude that 20-oxidation is the limiting step, rather than 3{beta}-hydroxylation, in the formation of GA1 and GA4 in elongating shoots of hybrid aspen, and that ectopic GA3ox expression alone cannot increase the flux toward bioactive GAs. Finally, several lines of evidence now suggest that GA4 has a more pivotal role in the tree hybrid aspen than previously believed.




This article has been cited by other articles:


Home page
 Plant Cell PhysiolHome page
L. Gallego-Giraldo, S. Ubeda-Tomas, C. Gisbert, J. L. Garcia-Martinez, T. Moritz, and I. Lopez-Diaz
Gibberellin Homeostasis in Tobacco is Regulated by Gibberellin Metabolism Genes with Different Gibberellin Sensitivity
Plant Cell Physiol., May 1, 2008; 49(5): 679 - 690.
[Abstract] [Full Text] [PDF]

Home page
 Plant Physiol.Home page
A. Radi, T. Lange, T. Niki, M. Koshioka, and M. J. P. Lange
Ectopic Expression of Pumpkin Gibberellin Oxidases Alters Gibberellin Biosynthesis and Development of Transgenic Arabidopsis Plants
Plant Physiology, February 1, 2006; 140(2): 528 - 536.
[Abstract] [Full Text] [PDF]


HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH
ASPB Publications PLANT PHYSIOLOGY® THE PLANT CELL
Copyright © 2004 by the American Society of Plant Biologists