Hormonal content and sensitivity of transgenic tobacco and potato plants expressing single rol genes of Agrobacterium rhizogenes T-DNA
Thomas Schmülling
1
*, Matthias Fladung
2
, Klaus Grossmann
3
and Jeff Schell
2
Plant J 3: 371-382.
1
Universität Tübingen, Lehrstuhl fⁿr Allgemeine Genetik, Auf der Morgenstelle 28, 72076 Tübingen, Germany
2
Max-Planck-Institut fⁿr Züchtungsforschung, Carl-von-Linné-Weg 10, 50829 Köln, Germany
3
Landwirtschaftliche Versuchsstation der BASF, 67117 Limburgerhof, Germany
Summary
The expression of single
rol
genes of the T
L
-DNA of Agrobacterium rhizogenes strain A4 in transgenic tobacco (
Nicotiana tabacum
L.) and potato (
Solanum tuberosum
L.) plants alters the internal concentrations of, and the sensitivity to, several plant hormones. The levels of immunoreactive cytokinins, abscisic acid, gibberellins and indole-3-acetic acid were analyzed in tissues of the apical shoots, stems, leaves, roots and undifferentiated callus tissue. The addition of the dominant and morphogenetically active
rolA
,
rolB
, or
rolC
genes resulted in alterations in the content of several hormones.
rolC
overexpression in particular led to an up to fourfold increase in the content of isopentenyladenosine, dihydrozeatin riboside and
trans
-zeatin riboside-type cytokinins in potato plants. This increase correlated well with different levels of expression of the
rolC
gene in different transgenic plants. Furthermore it was shown that the dwarfism of P
35S
-
rolC
transgenic tobacco and potato plants is correlated with a 28-60 % reduction of gibberellic acid A
1
concentration in apical shoots. Exogenous addition of gibberellic acid completely restored stem elongation in P
35S
-
rolC
transgenic plants. Apical shoots of dwarf
rolA
transgenic tobacco plants also contained 22% less gibberellic acid A
1
than control plants, but growth cannot be restored completly by exogeneously added gibberellic acid. Similarly, the sensitivity of transgenic tobacco seedlings or callus tissues towards different phytohormone concentrations can be altered by the expression of single
rol
genes. The overexpression of the
rolC
gene in seedlings led to an altered response to auxins, cytokinins, abscisic acid, gibberellic acid and the ethylene precursor ACC. The overexpression of the
rolB
gene in tobacco calli led to necrosis at lower auxin concentrations than in the wild type, while other parameters of auxin action, like the induction of cell division and growth, remained unchanged.