46
SIRKKA KUPILA-AHVENNIEMI AND EEVA THERMAN
cells presents many interesting problems of dedifferentiation. However,
in contradistinction to most animal neoplasms, a redifferentiation of cells
and even of whole organs takes place in crown gall. By varying the
conditions and the bacterial strain it is possible to obtain a whole range
of different galls, from so-called teratomata to fast-growing malignant
tumors. In general it can be said that crown gall is more under the
influence of the correlative forces of the host than animal tumors.
Crown gall tumorigenesis is known to involve the activation of a
number of growth substance systems. The fact that deoxyribonucleic
acid (DNA) synthesis seems to play an important—though as yet unexplained—role in this process furnishes a further link with differentiation phenomena in general. Tumor formation seems to have a number
of points in common even with apparently completely different phenomena such as flower induction.
The present paper is an attempt to review certain morphogenetic
aspects of the crown gall problem. The authors have—not unnaturally—
been influenced by their special fields of interest; anatomical as well as
cytological aspects are, therefore, in the foreground. Since in the past
the role of the wound has been surprisingly neglected, a detailed comparison of the observations made on normal and crown gall wounds is
given.
The literature on the crown gall problem is too vast to be reviewed
in any single publication, and the choices made reflect largely the
authors' interests. For those who feel that many important papers have
been omitted, an apologetic reference is made to the following reviews
which deal with other aspects of the problem: Beaud (1965), Bieber and
Wartenberg (1957), Braun and Stonier (1958), Braun (1962), Braun
and Wood (1961), Braun and Lipetz (1966), Kupila (1963), Mani (1964),
Stapp (1953).
II. The Occurrence of Crown Gall and
the Characteristics of the Bacteria
Crown gall is caused by Agrobacterium
tumefaciens
(Smith & Town.)
Conn, which is a bacterium commonly found in the ground all over the
world. It has the ability to induce tumors in a vast number of plant
species. Elliott (1951) has listed representatives of some 142 plant
genera belonging to 61 widely separated families that are susceptible to
the disease. Agrobacterium
tumefaciens consists of a number of strains
that differ not only in their virulence in general, but also in their
virulence toward different plant species. For example, Gadgil and Roy
SIRKKA KUPILA-AHVENNIEMI AND EEVA THERMAN
cells presents many interesting problems of dedifferentiation. However,
in contradistinction to most animal neoplasms, a redifferentiation of cells
and even of whole organs takes place in crown gall. By varying the
conditions and the bacterial strain it is possible to obtain a whole range
of different galls, from so-called teratomata to fast-growing malignant
tumors. In general it can be said that crown gall is more under the
influence of the correlative forces of the host than animal tumors.
Crown gall tumorigenesis is known to involve the activation of a
number of growth substance systems. The fact that deoxyribonucleic
acid (DNA) synthesis seems to play an important—though as yet unexplained—role in this process furnishes a further link with differentiation phenomena in general. Tumor formation seems to have a number
of points in common even with apparently completely different phenomena such as flower induction.
The present paper is an attempt to review certain morphogenetic
aspects of the crown gall problem. The authors have—not unnaturally—
been influenced by their special fields of interest; anatomical as well as
cytological aspects are, therefore, in the foreground. Since in the past
the role of the wound has been surprisingly neglected, a detailed comparison of the observations made on normal and crown gall wounds is
given.
The literature on the crown gall problem is too vast to be reviewed
in any single publication, and the choices made reflect largely the
authors' interests. For those who feel that many important papers have
been omitted, an apologetic reference is made to the following reviews
which deal with other aspects of the problem: Beaud (1965), Bieber and
Wartenberg (1957), Braun and Stonier (1958), Braun (1962), Braun
and Wood (1961), Braun and Lipetz (1966), Kupila (1963), Mani (1964),
Stapp (1953).
II. The Occurrence of Crown Gall and
the Characteristics of the Bacteria
Crown gall is caused by Agrobacterium
tumefaciens
(Smith & Town.)
Conn, which is a bacterium commonly found in the ground all over the
world. It has the ability to induce tumors in a vast number of plant
species. Elliott (1951) has listed representatives of some 142 plant
genera belonging to 61 widely separated families that are susceptible to
the disease. Agrobacterium
tumefaciens consists of a number of strains
that differ not only in their virulence in general, but also in their
virulence toward different plant species. For example, Gadgil and Roy