Gibberellins inhibit adventitious rooting in hybrid aspen and Arabidopsis by affecting auxin transport

Abstract

SUMMARYKnowledge of processes involved in adventitious rooting is important to improve both fundamental understanding of plant physiology and the propagation of numerous plants. Hybrid aspen (Populus tremula 3 tremulo€ ıdes) plants overexpressing a key gibberellin (GA) biosynthesis gene (AtGA20ox1) grow rapidly but have poor rooting efficiency, which restricts their clonal propagation. Therefore, we investigated the molecular basis of adventitious rooting in Populus and the model plant Arabidopsis. The production of adventitious roots (ARs) in tree cuttings is initiated from the basal stem region, and involves the interplay of several endogenous and exogenous factors. The roles of several hormones in this process have been characterized, but the effects of GAs have not been fully investigated. Here, we show that a GA treatment negatively affects the numbers of ARs produced by wild-type hybrid aspen cuttings. Furthermore, both hybrid aspen plants and intact Arabidopsis seedlings overexpressing AtGA20ox1, PttGID1.1 or PttGID1.3 genes (with a 35S promoter) produce few ARs, although ARs develop from the basal stem region of hybrid aspen and the hypocotyl of Arabidopsis. In Arabidopsis, auxin and strigolactones are known to affect AR formation. Our data show that the inhibitory effect of GA treatment on adventitious rooting is not mediated by perturbation of the auxin signalling pathway, or of the strigolactone biosynthetic and signalling pathways. Instead, GAs appear to act by perturbing polar auxin transport, in particular auxin efflux in hybrid aspen, and both efflux and influx in Arabidopsis.

ROOTING OF Araucaria angustifolia: TYPES OF CUTTINGS AND STOCK PLANTS SEX

“…Together with other substances, they act in the induction of rhizogenesis (WOODWARD;BARTEL, 2005;SAUER et al, 2013), suggesting the importance of cuttings position in branch (topophysis) on the quantity of rooting promoting substances, like auxins and carbohydrates. These substances carry out an essential function in the construction of necessary cellular structures for all plant physiological processes (LI et al, 2009;DENAXA et al, 2012;MAURIAT et al, 2014).…”

In vitro regeneration, Agrobacterium-mediated transformation, and genetic assay of chalcone synthase in the medicinal plant Echinacea pallida

“…The physiological functions of GA in root growth have been discussed for Arabidopsis (Tanimoto 2012;Mauriat et al 2014) and crosstalk between indole-3-acetic acid (IAA) and GA has been demonstrated in the signaling system (Fu and Harberd 2003;Gou et al 2010). Supplementation of GA 3 was reported to induce increases in secondary metabolite production and also affected cell viability and root morphogenesis of E. purpurea in hairy root cultures (Abbasi et al 2012).…”

Adventitious root formation in Arabidopsis : underlying mechanisms and applications

“…This consequently reduces auxin availability required for the induction of cell division (Mauriat et al, 2014;Niu et al, 2013). Despite its negative effect, GA was shown to promote AR formation through interactions with ethylene in deep water rice (Steffens et al, 2006).…”

“…AR formation is a complex heritable trait controlled by many endogenous and exogenous factors including light conditions, temperature, hormones (especially auxin), plant age, sugars, mineral salts and other molecules (Bellini et al, 2014). They may function as signals and induce groups of cells to redefine their fate, resulting in and regulating AR.…”

“…Gibberellic acid (GA3) inhibits AR formation in Arabidopsis hypocotyls (Mauriat et al, 2014), poplar cuttings (Busov et al, 2006) and in tomato (LombardiCrestana et al, 2012). In addition, treatment with GA biosynthesis inhibitors e.g., daminozide, paclobutrazol and triadimefon stimulate AR formation in mung bean hypocotyl cuttings and their effect was synergistic with IBA (Pan and Zhao, 1994).…”