Over-expression of a gibberellin 2-oxidase gene from Phaseolus coccineus L. enhances gibberellin inactivation and induces dwarfism in Solanum species

Abstract

Gibberellins (GAs) are endogenous hormones that play a predominant role in regulating plant stature by increasing cell division and elongation in stem internodes. The product of the GA 2-oxidase gene from Phaseolus coccineus (PcGA2ox1) inactivates C(19)-GAs, including the bioactive GAs GA(1 )and GA(4), by 2beta-hydroxylation, reducing the availability of these GAs in plants. The PcGA2ox1 gene was introduced into Solanum melanocerasum and S. nigrum (Solanaceae) by Agrobacterium-mediated transformation with the aim of decreasing the amounts of bioactive GA in these plants and thereby reducing their stature. The transgenic plants exhibited a range of dwarf phenotypes associated with a severe reduction in the concentrations of the biologically active GA(1) and GA(4). Flowering and fruit development were unaffected. The transgenic plants contained greater concentrations of chlorophyll b (by 88%) and total chlorophyll (11%), although chlorophyll a and carotenoid contents were reduced by 8 and 50%, respectively. This approach may provide an alternative to the application of chemical growth retardants for reducing the stature of plants, particularly ornamentals, in view of concerns over the potential environmental and health hazards of such compounds.

A Novel Class of Gibberellin 2-Oxidases Control Semidwarfism, Tillering, and Root Development in Rice

“…Overexpression of GA2oxs is an easy way to reduce GA levels in transgenic plants. However, constitutive ectopic overexpression of most GA2oxs caused severe dwarfism and low seed production in various plant species because active GAs were probably deactivated as soon as they were produced (Sakamoto et al, 2001;Singh et al, 2002;Schomburg et al, 2003;Biemelt et al, 2004;Lee and Zeevaart, 2005;Dijkstra et al, 2008). Expression of rice GA2ox1 under the control of the rice GA3ox2 promoter, at the site (shoot apex) of active GA biosynthesis, led to a semidwarf phenotype with normal flowering and grain development .…”

Horticultural characterization of a tetraploid transgenic plant of <i>Tricyrtis</i> sp. carrying the gibberellin 2-oxidase gene

“…On the other hand, overexpression of the GA2ox gene induced dwarf phenotypes in transgenic Arabidopsis thaliana, Nicotiana tabacum (Schomburg et al 2003), Torenia fournieri (Niki et al 2006), Solanum spp. (Dijkstra et al 2008), Brassica napus (Zhou et al 2012), Kalanchoe blossfeldiana and Petunia hybrida (Gargul et al 2013). Thus genetic transformation with the GA2ox gene may be an alternative approach to transformation with wildtype A. rhizogenes or the rol genes for producing dwarf ornamental plants.…”

Characterization of the Fungal Gibberellin Desaturase as a 2-Oxoglutarate-Dependent Dioxygenase and Its Utilization for Enhancing Plant Growth

“…Thus, the ectopically expressed desaturase should protect against high levels of 2b-hydroxylase activity, which has been shown to cause severe dwarfism in plants in which GA2ox genes are overexpressed (for review, see Phillips, 2004). This was tested by comparing N. sylvestris and S. nigrum plants transformed with the 35S:PcGA2ox1 gene (Dijkstra et al, 2008) with plants transformed also with 35S:des. Whereas in S. nigrum, only one of 10 plants expressing both transgenes showed recovery from the severely dwarfed phenotype, in N. sylvestris, all seven doubly transformed plants showed substantial growth restoration, although not to the height of nontransformed controls ( Fig.…”

“…The gelfiltered lysate (90 mL) was incubated with [ plants were obtained from tissue culture, but without incubation of leaf explants with A. tumefaciens and antibiotic selection. In order to obtain plants transformed with both 35S::des and 35S::PcGA2ox1, S. nigrum and N. sylvestris plants were transformed with A. tumefaciens strain LBA4404 harboring 35S::PcGA2ox1 in pLARS120 using the protocol described by Dijkstra et al (2008). Homozygous T2 35S::PcGA2ox1 plants obtained from T1 lines that demonstrated 3:1 segregation for the transgene were transformed with 35S::des, as described above.…”