Abstract
ARBORKNOX1 (ARK1), a poplar functional homolog of the Arabidopsis Class-I KNOTTED- like homeobox (KNOXI) transcription factor SHOOT MERISTEMLESS (STM), has been shown to have a role in maintaining meristematic cells in an undifferentiated state. Studies in which this gene was ectopically overexpressed identified a delay in the differentiation of cambial derivatives. Overexpression of ARK1 in poplar stem sectors, using the induced somatic sector analysis (ISSA) experimental system, was undertaken to further investigate its role in the differentiation of xylem fibre cells. ISSA involves the in vivo transformation of a small number of cambial cells in the stem with a gene of interest giving rise to a discreet transgenic tissue sector that can be directly compared to adjacent non-transgenic fibres to elucidate gene function. Phenotypes obtained were comparable with the proposed role of ARK1, where a delay in the development of the cell wall in differentiating fibre cells of active cambia was observed. Additional evidence suggests a role for ARK1 in the positive regulation of cell viability in the cambium. The significance of dormancy signals in the context of differentiation was also highlighted, as some transgenic fibres failed to fully differentiate prior to the onset of dormancy. Our findings are discussed in the context of wood formation and the use of ISSA as an experimental system.
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Abbreviations
- CK:
-
Cytokinin
- GA:
-
Gibberellic acid
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Acknowledgments
The authors would like to thank Hossein Valipour Kahrood for valuable and insightful feedback on the manuscript and Dr Andrew Groover for kindly providing the ARK1 gene. E. Melder was funded through an Australian Postgraduate Award through the Australian Research Council.
Data Archiving Statement
Data created as part of this study relates to the characterisation of morphological traits in the stems of trees and has not been submitted to any public database. Those wishing to access this data please contact the corresponding author.
Compliance with ethical standards
E. Melder and this work were funded through an Australian Postgraduate Award through the Australian Research Council. The authors report no conflicts of interest relating to the work presented here.
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Communicated by A. Brunner
This article is part of the Topical Collection on Gene Expression
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Supplementary Table 1
Average cell and lumen width in both the tangential and radial plane (including standard errors) for both the 35::ARK1 and GUS only vectors and adjacent non-transgenic tissue. (PDF 348 kb)
Supplementary Table 2
Average cell, lumen and cell wall area (including standard errors) for both the 35::ARK1 and GUS only vectors and adjacent non-transgenic tissue. (PDF 330 kb)
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Melder, E., Bossinger, G. & Spokevicius, A.V. Overexpression of ARBORKNOX1 delays the differentiation of induced somatic sector analysis (ISSA) derived xylem fibre cells in poplar stems. Tree Genetics & Genomes 11, 87 (2015). https://doi.org/10.1007/s11295-015-0912-8
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DOI: https://doi.org/10.1007/s11295-015-0912-8