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Auxin biosynthesis and homeostasis in Arabidopsis thaliana in relation to plant growth and development

Ljung, Karin (2002). Auxin biosynthesis and homeostasis in Arabidopsis thaliana in relation to plant growth and development. Diss. (sammanfattning/summary) Umeå : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae. Silvestria, 1401-6230 ; 243
ISBN 91-576-6327-0
[Doctoral thesis]

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The auxin indole-3-acetic acid (IAA) is a growth regulating substance important for many developmental processes during the life cycle of plants. The papers presented in this thesis address different aspects of IAA biosynthesis, metabolism and transport. The model plant Arabidopsis thaliana was used for most of the studies, but some studies were also performed on Scots pine (Pinus sylvestris). We developed very sensitive and selective mass spectrometric analytical techniques that made it possible to perform tissue specific IAA quantification and IAA biosynthesis rate measurements on small amounts of plant tissue. We observed that seeds utilised stored IAA (in the form of ester- and amide-linked conjugates) for elongation growth during the initial germination phase. IAA biosynthesis and catabolism were initiated later in the germinating seedling, and these processes appear to be tightly regulated in order to maintain IAA homeostasis in the developing tissues. High concentrations of IAA were observed in young developing leaves and tissues with high rates of cell division. Perturbation in the IAA concentration within the leaf lowered leaf expansion, and feedback inhibition of IAA biosynthesis was observed after NPA treatment to block polar auxin transport. The youngest developing leaves exhibited the highest IAA biosynthesis rates, but all parts of young seedlings, including the root, showed IAA synthesis capacity. We demonstrated that transport of IAA from the shoot to the root is essential for the emergence of lateral root primordia, and that a basipetal IAA gradient is present in the root tip. We also showed that this gradient is probably generated by the cellular localisation of auxin influx and efflux carriers, directing the flow of auxin coming from the aerial parts of the plant to specific cell types within the root tip. In addition to IAA synthesised in the shoot and then transported to the root system via polar auxin transport and/or transport in the phloem, we demonstrated that a source of IAA is located within the root tip.

Authors/Creators:Ljung, Karin
Title:Auxin biosynthesis and homeostasis in Arabidopsis thaliana in relation to plant growth and development
Series Name/Journal:Acta Universitatis Agriculturae Sueciae. Silvestria
Year of publishing :April 2002
Number of Pages:51
ALLI. Ljungk K.*, Östin, A.*, Lioussanne, L. and Sandberg, G. (2001). Developmental regualtion of indole-3-acetic acid turnover in Scots pine seedlings. Plant Physiol. 125, 464-475. II. Ljung, K., Bhalerao, R.P. and Sandberg, G. (2001). Sites and homeostatic control of auxin biosynthesis in Arabidopsis during vegetative growth. Ölant J. 28, 465-474. III. Bhalerao, R.P.*, Eklöf, J.*, Ljung, K.*, Marchant, A., Bennett, M. and Sandberg, G. (2002). Shoot-derived auxin is essential for early lateral root emergence in Arabidopsis seedlings. Plant J. 29, 325-332. IV. Ljung, K. and Sandberg, G. (2002). Auxin biosynthesis in Arabidopsis root apical tissue. (Manuscript). V. Swarup, R., Friml, J., Marchant, A., Ljung, K., Sandberg, G., Palme, K. and Bennett, M. (2001). Localization of the auxin permease AUX1 suggests two functionally distinct hormone transport pathways operate in the Arabidopsis root apex. Genes Dev. 15, 2648-2653. VI. Friml, J., Benková, E., Blilou, I., Wisniewska, J., Hamann, T., Ljung, K., Woody, S., Sandberg, G., Scheres, B., Jürgens, G. and Palme. K. (2002). AtPIN4 mediaties sink-driven auxin gradients and root patterning in Arabidopsis. Cell 108, 661-673. * To be considered joint first authors.
Place of Publication:Umeå
ISBN for printed version:91-576-6327-0
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:F Plant production > F62 Plant physiology - Growth and development
Subjects:Not in use, please see Agris categories
Agrovoc terms:arabidopsis thaliana, pinus sylvestris, iaa, biosynthesis, metabolism, homeostasis, germination, cell division, roots, phloem
Keywords:auxin, biosynthesis, feedback inhibition, metabolism, homeostasis, cell division, leaf development, lateral root development, polar auxin transport, phloem transport, gradient
Permanent URL:
ID Code:227
Department:(S) > Dept. of Forest Genetics and Plant Physiology
Deposited By: Staff Epsilon
Deposited On:11 Apr 2003 00:00
Metadata Last Modified:02 Dec 2014 10:02

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