The rat glucocorticoid receptor integration in Nicotiana langsdorffii genome affects plant responses to abiotic stresses and to arbuscular mycorrhizal symbiosis

Abstract

The present study reports evidence of the pleiotropic effects caused by the insertion of the rat glucocorticoid receptor (GR) into the genome of Nicotiana langsdorffii. Transgenic N. langsdorffii-GR plants and the wild-type genotypes were analysed for their phenotypic and physiological characteristics. The integration of the GR gene affected flowering, growth habit, leaf morphology and stomatal pattern. Furthermore, GR plants showed an increased tolerance to heavy metal, drought and heat stress as evidenced by electrolyte leakage and by cell dedifferentiation and differentiation capability after recovery from stress treatments. We also monitored the establishment of the beneficial symbiosis between transgenic plants and the mycorrhizal fungus Funneliformis mosseae whose presymbiotic growth was significantly reduced by root exudates of N. langsdorffii-GR plants. The observed pleiotropic responses of transgenic plants may be a consequence of the hormonal imbalance, putatively due to the interaction of the GR receptor with the host genetic background. Our findings suggest that N. langsdorffii-GR plants can be used as a functional model system for the study of plant responses to a series of environmental stimuli.

Inorganic markers profiling in wild type and genetically modified plants subjected to abiotic stresses

“…The transformation of N. langsdorffii plants with both GR gene and rolC gene induced significant differences in both morphology and growth [24,34]. The exposure to the water stress due to the growth of plants for 15 days on LS medium containing 20% PEG, induced a clear wilting effect only on untransformed plants, while GR and rolC transgenic plants did not show any stress symptom.…”

“…Plant modification, incubation and growth were carried out at the former Department of Evolutionary Biology "Leo Pardi" (now Department of Biology), University of Florence, by Prof. M. Buiatti and Dr. P. Bogani. The modified plants were obtained and characterized following the procedure described elsewhere [19,23,24].…”

“…. Polyethylene glycol (PEG) was added to dehydrate the LS medium (described in Bogani et al [24]). PEG is widely used to modify the osmotic potential of nutrient solution cultures and to induce plant water deficit in a relatively controlled manner, appropriate to experimental protocols.…”

Simultaneous determination of shikimic acid, salicylic acid and jasmonic acid in wild and transgenic Nicotiana langsdorffii plants exposed to abiotic stresses

“…The gr-modified plants were obtained by inserting a rat gene encoding the glucocorticoid receptor, containing the constitutive CaMV promoter; it is possible that plant phyto-steroids, and particularly brassinosteroids, which showed to induce tolerance towards oxidative, drought and heavy metal stresses (Bartwal et al, 2013), have sufficient affinity with the rat glucocorticoid receptor protein and, therefore, can be activated by this signaling chain in gr transgenic plants. The gr insertion in N. langsdorffii has shown to determine the reduction of plant size, the decrease of electrolyte leakage and the increase of water content (Bogani et al, 2015). The integration of the rolC gene in plants reduced plant size, electrolyte leakage and root and shoot dry biomass (Ancillotti et al, 2015), while increased phytoalexin production and the expression of pathogenesis-related proteins (Bulgakov et al, 2008); rolC insertion, moreover, has been related to an increased activity of cytokinins and to the induction of many secondary metabolite pathways (Kiselev et al, 2006).…”

“…The aim of this paper is to investigate the effects of Cr(VI) exposure, water deficiency and high temperature on wild and transgenic N. langsdorffii plants, through the analysis of selected metabolites, in order to highlight the influence of the inserted transgenes (rolC and gr genes) on plant stress responses. The morphological and physiological effects of rolC and gr insertion in N. langsdorffii plants, exposed to heat, water and chemical stresses, have been the subject of other studies (Bogani et al, 2015;Ancillotti et al, 2015).…”