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This article is part of the supplement: IUFRO Tree Biotechnology Conference 2011: From Genomes to Integration and Delivery

Open Access Oral presentation

Enhanced cytokinin signaling stimulates cell proliferation in cambium of Populus

Juha Immanen1*, Kaisa Nieminen2, Jing Zhang1, Rishi Bhalerao3 and Ykä Helariutta1

Author Affiliations

1 University of Helsinki, Finland

2 University of Lausanne, Switzerland

3 Umeå Plant Science Center, Sweden

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BMC Proceedings 2011, 5(Suppl 7):O23  doi:10.1186/1753-6561-5-S7-O23

The electronic version of this article is the complete one and can be found online at:

Published:13 September 2011

© 2011 Immanen et al; licensee BioMed Central Ltd.

This is an open access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Understanding the regulation of radial growth that underlies wood development is of great importance for future use of tree products as a renewable resource. For this purpose, we have performed a detailed analysis of cytokinin function in the regulation of cambial development in a tree stem. Furthermore, we have identified potential cytokinin signaling response genes active during the secondary development in Arabidopsis and currently studying the best candidate genes also in Populus.

Results and discussion

In the cambium, expression of cytokinin receptor genes peaks in the actively dividing cells. This indicates that cytokinin signaling pathway is a major regulator of cambial cell proliferation. We have previously shown in transgenic Populus trees that we can slow down the cambial activity by reducing the level of cytokinin signaling in it [1]. To study if cytokinin signaling is truly a rate-limiting process for cambial activity, we have now engineered transgenic Populus trees with an enhanced cambial cytokinin signaling level. In these trees, we were able to see that elevated cytokinin signaling stimulated the cambial cell division activity and led to increased biomass production. Furthermore, based on microarray profiling in Arabidopsis, we have been able to identify several transcription factors functioning downstream of cytokinin signaling during the secondary development. These transcriptional regulators have stimulatory effect on radial growth in Arabidopsis root. We are currently studying if the Populus orthologs of these genes have similar function in the cambium of the tree stem.


We have shown that the cambial cell division activity, and through it the production of stem biomass, can be enhanced or decreased through elevated or decreased cytokinin signaling. Together, our results show that cytokinins are major rate-limiting hormonal regulators of cambial development. Our study provides potential for applied research towards future breeding of faster growing tree cultivars.


  1. Nieminen K, Immanen J, Laxell M, Kauppinen L, Tarkowski P, Dolezal K, Tähtiharju S, Elo A, Decourteix M, Ljung K, Bhalerao R, Keinonen K, Albert VA, Helariutta Y: Cytokinin signaling regulates cambial development in poplar.

    Proc Natl Acad Sci U S A 2008, 105(50):20032-20037. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL