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observations firstly suggested that there is a similarity between the auxin-mediated
effects and morphogenic effects of
rol
B. However, further studies demonstrated
that an auxin-induced hyperpolarization at the plasma membrane is exhibited by
rol
B-transformed plants. The morphogenic effects of
rol
B involve changes in either
the responsiveness to auxin or in auxin content (Cardarelli et al.
1987b
; Shen et al.
1988
; Capone et al.
1989
; Maurel et al.
1991
). Activation of auxin-induced hyper-
polarization through H
+
ATPase protein pump at the plasma membrane appears to
be related to the proton excretion (Ephritikhine et al.
1987
; Keller and Van Volken-
burgh
1998
).
rol
B gene causes transformed plant cells to bind more auxin than wild
type and the additional auxin-binding activity is completely abolished by using anti-
RolB antibodies (Filippini et al.
1994
; Shoja
2010
).
Estruch et al. (
1991
) reported that RolB protein exhibits a β-glucosidase activ-
ity able to hydrolyze biologically active indole-3-glucosidese. It can be explained
by the increased auxin perception and sensitivity with releasing the hormone from
β-glucoside conjugates. As a result of increase concentration of auxin cause the
phenotypic alterations observed in
rol
B transgenic tissues (Shen et al.
1988
,
1990
;
Maurel et al.
1991
,
1994
; Meyer et al.
2000
). However, later studies showed that
neither the intracellular concentration nor the metabolism of auxin was changed
by
rol
B expression in plant cells. Rather, the increased auxin sensitivity of
rol
B-
transformed cells results from alterations in the reception/transduction of the auxin
signal (Nilsson et al.
1993b
; Schmülling et al.
1993
; Delbarre et al.
1994
; Bellin-
campi et al.
1996
; Veena and Taylor
2007
).
Overexpressing
rol
B gene under a constitutive promoter in transgenic plants
suppresses adventitious root induction (Spena et al.
1987
) and necrosis in callus
tissues and leaves of young plants (Schmulling et al.
1988
). Both callus and root
formations at wound sites are cancelled if mutations occur in
rol
B gene (Vilaine and
Casse-Delbart
1987
). Normal growth of these organs depends upon the expression
level of
rol
B gene necessary for active growth of hairy roots. A high or low level
of expression correlates with impaired growth of these organs (Tanaka et al.
2001
;
Veena and Taylor
2007
).
A. rhizogenes rol
genes enhance the biosynthesis of certain groups of secondary
metabolites in transformed plant cells. It was shown that
rol
B is apparently the most
powerful inducer of secondary metabolism and at the same time, the most important
inhibitor of callus growth (Palazon et al.
1998
; Bonhomme et al.
2000
; Bulgakov
et al.
2002a
; Shkryl et al.
2008
; Shoja
2010
).
rol
B gene mediated stimulatory effect
on resveratrol and anthraquinone production suppresses with the tyrosine phospha-
tase inhibitors proven that RolB also has tyrosine phosphatase activity (Filippini
et al.
1996
; Kiselev et al.
2007
).
rol
C
The
rol
C gene sequences vary in different strains but their sizes are similar and
ranging between 537 bp (strain 8196) to 543 bp (strain 2659, 1724 and A4).
rol
C
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