Abstract
The phytohormone gibberellin (GA) promotes plant growth by stimulating cellular expansion. Whilst it is known that GA acts by opposing the growth-repressing effects of DELLA proteins, it is not known how these events promote cellular expansion. Here we present a time-lapse analysis of the effects of a single pulse of GA on the growth of Arabidopsis hypocotyls. Our analyses permit kinetic resolution of the transient growth effects of GA on expanding cells. We show that pulsed application of GA to the relatively slowly growing cells of the unexpanded light-grown Arabidopsis hypocotyl results in a transient burst of anisotropic cellular growth. This burst, and the subsequent restoration of initial cellular elongation rates, occurred respectively following the degradation and subsequent reappearance of a GFP-tagged DELLA (GFP-RGA). In addition, we used a GFP-tagged α-tubulin 6 (GFP-TUA6) to visualise the behaviour of microtubules (MTs) on the outer tangential wall (OTW) of epidermal cells. In contrast to some current hypotheses concerning the effect of GA on MTs, we show that the GA-induced boost of hypocotyl cell elongation rate is not dependent upon the maintenance of transverse orientation of the OTW MTs. This confirms that transverse alignment of outer face MTs is not necessary to maintain rapid elongation rates of light-grown hypocotyls. Together with future studies on MT dynamics in other faces of epidermal cells and in cells deeper within the hypocotyl, our observations advance understanding of the mechanisms by which GA promotes plant cell and organ growth. © 2011 Blackwell Publishing Ltd.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 628-639 |
| Number of pages | 12 |
| Journal | The Plant Journal |
| Volume | 69 |
| Issue number | 4 |
| DOIs | |
| State | Published - Nov 25 2011 |
| Externally published | Yes |
Bibliographical note
KAUST Repository Item: Exported on 2020-10-01Acknowledged KAUST grant number(s): KUK-I1-002-03
Acknowledgements: We thank Chris Hindle and John Humble from the workshop at the John Innes Centre for building the growth tracking chamber. We thank Enrico Coen for useful discussions on growth. We thank Jinrong Peng for provision of the ga1-3 (Col-0) line. We thank Jordi Chan for provision of the P35S:GFP-TUA6 line and for interesting discussions. We thank Paul Southam for help with IMAGEJ. We thank Rene Dreos for help with statistics. This work was funded by the Biotechnology and Biological Sciences Research Council (Core Strategic Grant to the John Innes Centre and Response Modes Grant BB/D521665/1) and by a Beatriu de Pinos post-doctoral fellowship from the Generalitat de Catalunya (2005 BP-A 10110) to SSG. This work was supported in part by award no. KUK-I1-002-03 (to NPH) made by King Abdullah University of Science and Technology (KAUST).
This publication acknowledges KAUST support, but has no KAUST affiliated authors.