Abstract
Under identical culture conditions, only 8 out
of 12 species and subspecies of the genus
Daucus proved
capable of somatic embryogenesis. Random amplified
polymorphic DNA analysis indicated a polymorphism
between the genomes of individual species that were capable
of embryogenesis and those that were not. Two
specific bands (1.1 kbp, 0.68 kbp) were detected only in
the genomes of individuals with the capacity for embryogenesis.
These were cloned and sequenced, and the homology
of the nucleotide sequences of the various species
was detected: this ranged from 74% to 92% for the
larger sequence and from 92% to 97% for the smaller
one. These DNA sequences would appear to be useful as
a marker of the capacity for somatic embryogenesis in
the genus
Daucus.
Keywords
Daucus · DNA marker · Random amplified
polymorphic DNA · Somatic embryogenesis
Abbreviations
IAA: Indole-3-acetic acid ·
PCR:
Polymerase chain reaction · RAPD: Random
amplified polymorphic DNA ·
2D-PAGE:
Two-dimensional polyacrylamide gel
electrophoresis
Introduction
Although there is a continuous steady increase in the
number of species of higher plants for which protocols to
induce somatic embryogenesis have been reported, little
is understood about this developmental process. Genetic
factors related to the recalcitrance to somatic embryogenesis
have been discussed for one or the other species and
even for varieties of one species (Vasil 1984), but no conclusive
evidence for a direct genetic correlation at the
molecular level has yet been reported. In order to gain a
better understanding of the significance of genetic factors
for detecting possible markers for somatic embryogenesis,
we conducted studies at the DNA level under identical
experimental conditions on selected regenerative and
non-regenerative
Daucus species and subspecies.
In the investigation reported here we initially tested
the embryogenic capacity of 12
Daucus species or subspecies;
of these, 8 were successfully induced to undergo
somatic embryogenesis through the use of cultured petiole
explants. It appears that a finely tuned developmental
program is initiated in these explants when they are
placed into a medium containing an auxin. Following extensive
biochemical and histological investigations,
which also included a study of transgenic plant material
containing a mannopine synthase promoter/glucuronidase
reporter gene to observe auxin distribution within
cultured explants (Li and Neumann 1985; Neumann and
Grieb 1992; Neumann 1995, 2000; Grieb et al. 1997;
Imani 1999; Imani et al. 1999), we propose that this developmental
program is as follows.
Upon the initiation of embryogenesis, the endogenous
auxin is more or less evenly distributed among the cells
of the explanted petiole sections. After 3–4 days of culture
in an IAA-supplemented nutrient medium, a large
increase in cytoplasmic volume occurs near the vascular
bundles in cells that were previously vacuolated; this is
followed by the initiation of cell division. After 7 days of
culture, an accumulation of IAA can be observed in cells
near the vascular bundles, leaving the other tissue almost
free of IAA. Concurrently, the initiation of root primor-
Communicated by K.K. Kamo
J. Imani · L. Tran Thi · B. Arnholdt-Schmitt · C. Lein
K.-H. Neumann (
✉)
Institute of Plant Nutrition, Division of Plant Tissue Culture,
Justus Liebig University, Heinrich-Buff-Ring 26-32,
35392 Giessen, Germany
e-mail: Karl-Hermann.Neumann@ernaehrung.uni-giessen.de
Tel.: +49-641-9939190, Fax: +49-641-9939199
G. Langen
Institute for Phytopathology, and Applied Zoology,
Justus Liebig University, Heinrich-Buff-Ring 26-32,
35392 Giessen, Germany
S. Roy · A. Kumar
Biotechnology Laboratory, Department of Botany,
University of Rajasthan, Jaipur 302004, India
Plant Cell Rep (2001) 20:537–541
DOI 10.1007/s002990100363
GENETICS AND GENOMICS
J. Imani · L. Tran Thi · G. Langen
B. Arnholdt-Schmitt · S. Roy · C. Lein · A. Kumar
K.-H. Neumann
Somatic embryogenesis and DNA organization of genomes
from selected
Daucus species
Received: 17 November 2000 / Accepted: 22 May 2001 / Published online: 5 July 2001
© Springer-Verlag 2001
