Wood formation in rolC transgenic aspen trees

Abstract Wood formation and structure of 3-year-old 35S-rolC transgenic aspen (Populus tremula L. × tremuloides Michx.) were compared with the situation in non-transformed control aspen trees. The transgenics are characterized by reduced shoot growth and an earlier bud break. Their wood formation did not immediately follow bud break and leaf development but occurred after some delay, about the same time as wood formation was initiated in the control trees. Quantitatively, the wood structure of the transgenics and of the non-transformed controls was not significantly different; therefore the dwarfism of the transgenics is very likely due to a reduction in cell number. Atypical formation of latewood led to the assumption that the differentiation of cells is decelerated. Additionally, cells lacked both secondary walls and normal lignification, and discoloration of the wood and the formation of tyloses were conspicuous in all transgenics. In contrast, they did not occur in the non-transformed control aspen trees. The observations are discussed in relation to the widely accepted auxin hypothesis. It is suggested that 35S-rolC transgenic aspen trees may be a useful model to study the regulatory mechanisms of wood formation.

[1]  A. Altman,et al.  rol-Transgenic Populus tremula: root development, root-borne bud regeneration and in vitro propagation efficiency , 1998, Trees.

[2]  M. Van Montagu,et al.  Gene discovery in the wood-forming tissues of poplar: analysis of 5, 692 expressed sequence tags. , 1998, Proceedings of the National Academy of Sciences of the United States of America.

[3]  T. Itoh,et al.  The Dam-Up Effect of Morphactin in Broad-LeavedTree Stems Evidence of the Downward Spread of Auxin , 1991 .

[4]  R. Aloni.  The Induction of Vascular Tissues by Auxin and Cytokinin , 1995 .

[5]  J. Cairney,et al.  Clonal forestry genetic engineering : Where we stand, future prospects, and potential impacts on mill operations , 1998 .

[6]  S. Regan,et al.  Accurate and high resolution in situ hybridization analysis of gene expression in secondary stem tissues. , 1999, The Plant journal : for cell and molecular biology.

[7]  R. Sederoff,et al.  Genetic Regulation of Lignin Biosynthesis and the Potential Modification of Wood by Genetic Engineering in Loblolly Pine , 1994 .

[8]  H. Fukuda.  Tracheary Element Differentiation. , 1997, The Plant cell.

[9]  S. Howell.  7 – Transgenic Plants for Studying Responses to the Hormones Auxin and Cytokinin , 1993 .

[10]  T. Schmülling,et al.  Hormonal content and sensitivity of transgenic tobacco and potato plants expressing single rol genes of Agrobacterium rhizogenes T‐DNA , 1993 .

[11]  O. Nilsson,et al.  Getting to the root: The role of the Agrobacterium rhizogenes rol genes in the formation of hairy roots , 1997 .

[12]  M. Fladung.  Transformation of Diploid and Tetraploid Potato Clones with the rol C Gene of Agrobacterium rhizogenes and Characterization of Transgenic Plants , 1990 .

[13]  K. Shimaji,et al.  The pinning method for marking xylem growth in hardwood species , 1984 .

[14]  H. Klee,et al.  The Roles of Phytohormones in Development as Studied in Transgenic Plants , 1994 .

[15]  B. Sundberg,et al.  Altered Growth and Wood Characteristics in Transgenic Hybrid Aspen Expressing Agrobacterium tumefaciens T-DNA Indoleacetic Acid-Biosynthetic Genes , 1995, Plant physiology.

[16]  G. Sandberg,et al.  Hormonal Characterization of Transgenic Tobacco Plants Expressing the rolC Gene of Agrobacterium rhizogenes TL-DNA , 1993, Plant physiology.

[17]  A. Altman,et al.  rol-Gene expression in transgenic aspen (Populus tremula) plants results in accelerated growth and improved stem production index , 1999, Trees.

[18]  T. Schmülling,et al.  Independent and synergistic activity of rol A, B and C loci in stimulating abnormal growth in plants , 1987, The EMBO journal.

[19]  M. Sack,et al.  Growth dynamics in wood formation of plantation-grown Swietenia macrophylla King and Carapa guianensis Aubl. , 1999 .

[20]  M. R. Ahuja,et al.  Gene transfer in aspen , 1996 .

[21]  K. Grossmann,et al.  The plant oncogene rolC is responsible for the release of cytokinins from glucoside conjugates. , 1991, The EMBO journal.

[22]  M. R. Ahuja,et al.  Morphological Changes in Transgenic Populus Carrying the RolC Gene from Agrobacterium rhizogenes , 1996 .

[23]  R. Sederoff,et al.  Genetic engineering of wood , 1991 .

[24]  N. Chaffey.  Cambium: old challenges – new opportunities , 1999, Trees.

[25]  M. R. Ahuja,et al.  Alterations in hormonal and developmental characteristics in transgenic Populus conditioned by the rolC gene from Agrobacterium rhizogenes , 1997 .

[26]  R. Savidge,et al.  Xylogenesis, Genetic and Environmental Regulation-A Review- , 1996 .

[27]  B. Sundberg,et al.  Indole-3-acetic acid controls cambial growth in scots pine by positional signaling , 1998, Plant physiology.