Abstract
To gain insight into the relationship between oxidative stress and somatic embryogenesis (SE) induction, we analysed the effects of a reduced glutathione (GSH) of antioxidant activity on the embryogenic potential of in vitro cultured explants of the model plant Arabidopsis. The results showed that the GSH treatment resulted in SE induction in the explants that had been cultured on an auxin-depleted medium. The GSH-induced SE was shown to be associated with auxin biosynthesis and the accumulation of both the YUCCA transcripts (YUC10/11) and the indolic compounds that are indicative for IAA. Inversely, 2,4-D treatment was found to increase the GSH level in the cultured explants and thus, complex interactions between the auxin and oxidative stress were assumed to control SE induction. The genetic regulators of auxin-induced SE, the LEC1 and LEC2 genes, were also up-regulated in the GSH-triggered SE. In contrast, the expression profiles of BBM and MYB118 were distinctly different in the GSH- than in 2,4-D-induced SE, which suggests differences in the genetic regulation of these alternative embryogenic pathways. Collectively, the study provides evidence that the GSH-imposed changes in the oxidative stress level affect auxin production, which triggers embryogenic development in the cultured explants.
Highlights
Somatic embryogenesis (SE) is a unique plant-specific developmental process in which the differentiated somatic cells of plants produce somatic embryos (Jiménez 2001)
In order to assess the role of oxidative stress in the embryogenic response of plant tissues that are cultured in vitro, GSH was used to treat the Arabidopsis explants of immature zygotic embryos
To evaluate embryogenic effectiveness of the GSH, explants that had been treated with 0.1 (E0G0.1) and 0.5 (E0G0.5) mM of GSH were analysed in terms of the percentage of embryogenic explants (SE efficiency) and the average number of somatic embryos that had been produced per embryogenic explant (SE productivity) (Fig. 2)
Summary
Somatic embryogenesis (SE) is a unique plant-specific developmental process in which the differentiated somatic cells of plants produce somatic embryos (Jiménez 2001). SE provides an experimental system in studies on the genetic and physiological determinants of the developmental plasticity of plant somatic cells. In addition to its auxin-like activity, 2,4-D has been postulated to trigger SE through a stress response-related mechanism (Fehér 2015). In line with this assumption, a differential expression of the stress-related genes in 2,4-D-induced embryogenic cultures of Arabidopsis (Gliwicka et al 2013) and other plants (Thibaud-Nissen et al 2003; Sun et al 2012) was reported. Numerous studies have demonstrated the role of stress responses in the embryogenic transition of somatic plant cells, the relationship between stress and the SE induction mechanism remains unclear (Zavattieri et al 2010)
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