Agrobacterium rhizogenes-Mediated Transformation and Its Biotechnological Applications in Crops - Crop Improvement: New Approaches and Modern Techniques - page 14

Table 1.1 (continued)

Gene Protein Function Phenotype

ORF8 Fusion protein

consisting of
N-terminal
domain (NORF8)
and C-terminal
part (CORF8)
Tryptophan monoox-
ygenase activity

Modifies sucrose transport
N-terminal domain causes
sugar/starch accumulation
C-terminal domain reduces
sugar/starch accumulation

Growth retardation, chlo-
rotic and necrotic leaves
and accumulation of high
levels of sugars (glucose,
fructose and sucrose) and
starch

ORF13 Contains a con-
servative
retinoblastoma
(RB)-binding
motif LxCxE

Hormone homeostasis and
regulation of the cell cycle
Increases number of mitoses
in shoot apical meristem
Induces dedifferentiation (pre-
requisite to competence)
Graft transmissible

Induce cell proliferation
such as dense green and
rapidly proliferating cal-
lus, including irregular
formation of leaves,
severe leaf nervure,
shortened and variable
internode length, abnor-
mal and asymmetric
flowers, agravitropic root
growth and a reduced
cell number and cell size
in the root

ORF13a Tissue specific
manner in plants,
primarily in leaf
vascular tissues
May interact directly
with DNA
SPXX repeat motif

Necessary for root induction
Regulatory function of itself

Not yield a visible
phenotype

ORF14 Auxin like effect Act together with ORF13 to

induce root induction

No morphological change

observed in N. tabacum . The reduction ratio depends on tissue type and growth stage
of the plant (Dehio et al. 1993 ). It was demonstrated that despite low level of auxin
concentration, auxin sensitivity is enhanced in transgenic plants (Maurel et al. 1991 ;
Vansuyt et al. 1992 ). Additionally, the effects of rol A can be attenuated, probably
through methylation (Martin-Tanguy et al. 1996 ; Lee et al. 2001 ). Inactivation of
rol A leads to the formation of long, straight roots giving a less compact appearance
on Kalanchoe daigremontiana leaves (Vilaine and Casse-Delbart 1987 ). Transgenic
N. tabacum plants are also show stunted growth, dark green wrinkled leaves with an
altered length to width ratio, condensed inflorescences, retarded onset of flowering,
a reduced number of flowers and compact styles (Dehio et al. 1993 ).
A. rhizogenes infected plant tissues are 100 times more sensitive to auxin than
normal phenotype exhibiting plant tissues. This suggests that the increased sensitiv-
ity of transformed plants should not be due to a particular insertion position of the
rol A gene in the transgenic plant genome, but rather reflects the effect(s) of the rol A
gene product (Vansuyt et al. 1992 ). It was found that N. tabacum leaves of rol A