Cytokinin-induced activity of antioxidant enzymes in transgenic Pssu-ipt tobacco during plant ontogeny

Abstract

Cytokinin (CK) content and activities of several antioxidant enzymes were examined during plant ontogeny with the aim to elucidate their role in delayed senescence of transgenic Pssu-ipt tobacco. Control Nicotiana tabacum L. (cv. Petit Havana SR1) and transgenic tobacco with the ipt gene under the control of the promoter of small subunit of Rubisco (Pssu-ipt) were both grown either as grafts on control rootstocks or as rooted plants. Both control plant types showed a decline in total content of CKs with proceeding plant senescence. Contrary to this both transgenic plant types exhibited at least ten times higher content of CKs than controls and a significant increase of CK contents throughout the ontogeny with maximal values in the later stages of plant development. Significantly higher portion of O-glucosides was found in both transgenic plant types compared to control ones. In transgenic plants, zeatin and zeatin riboside were predominant type of CKs. Generally, Pssu-ipt tobacco exhibited elevated activities of antioxidant enzymes compared to control tobacco particularly in the later stages of plant development. While in control tobacco activity of glutathione reductase (GR) and superoxide dismutase (SOD) showed increasing activity up to the onset of flowering and then gradually decreased, in both transgenic types GR increased and SOD activity showed only small change throughout the plant ontogeny. Ascorbate peroxidase (APOD) was stimulated in both transgenic types. The manifold enhancement of syringaldazine and guaiacol peroxidase activities was observed in transgenic grafts throughout plant ontogeny in contrast to control and transgenic rooted plants, where the increase was found only in the late stages. Electron microscopic examination showed higher number of crystallic cores in peroxisomes and abnormal interactions among organelles in transgenic tobacco in comparison with control plant. The overproduction of cytokinins resulted in the stimulation of activities of AOE throughout the plant ontogeny of transgenic Pssu-ipt tobacco.Additional key words: ascorbate peroxidase, catalase, glutathione reductase, guaiacol peroxidases, superoxide dismutase, syringaldazine peroxidase.⎯⎯⎯⎯ sequence of the gene coding for small subunit of Rubisco; SPOD -syringaldazine peroxidase; SOD -superoxide dismutase; T -transgenic rooted plants; T/C -transgenic grafts; TEM -transmission electron microscopy.

The effect of natural and synthetic auxins on the growth, metabolite content and antioxidant response of green alga Chlorella vulgaris (Trebouxiophyceae)

“…Some literature data indicates that auxins can increase in the activity of antioxidant enzymes regulating ROS levels, which could be associated with the activation of embryo/ organogenesis (Synková et al 2006). Moreover, exogenous natural (IAA) and synthetic (2,4-D) auxins can stimulate the activities of antioxidant enzymes, such as CAT, SOD and peroxidases leading to a regeneration (shoot production) process in wheat (T. aestivum L.) tissue (Szechyńska-Hebda et al 2007).…”

“…ROS can interact with other signal molecules, including phytohormones in the regulation of these physiological responses. It is suggested that plant growth regulators can modify the synthesis of antioxidants and the activity of basic antioxidant enzymes, and some of these enzymes are also implicated in phytohormone catabolism (Synková et al 2006). Our knowledge about the physiological and molecular aspects of interaction between auxin and ROS is rapidly expanding.…”

Effects of cytokinins on antioxidant enzymes in in vitro grown shoots of Pelargonium hortorum L. H. Bayley

“…Enzymatic protection is partly performed by superoxidase dismutases (SOD) that dismutate •O 2 -radicals to H 2 O 2 and by catalase (CAT) and various peroxidases that degrade H 2 O 2 [5,8]. The activity of the scavenging enzymes is regulated by different factors, including hormone treatments [9,10].…”

A Novel Protective Function for Cytokinin in the Light Stress Response Is Mediated by the ARABIDOPSIS HISTIDINE KINASE2 and ARABIDOPSIS HISTIDINE KINASE3 Receptors

“…Cytokinin acts as a signal for photosynthetic acclimation to canopy light gradients (Boonman et al, 2007) and shadeinduced leaf growth arrest (Carabelli et al, 2007). Exogenous application of cytokinin stimulates the transition from etioplast to chloroplast in detached leaves and cell cultures, increases the rate of grana and stroma lamella, and extends the life span of chloroplasts (Parthier, 1979;Catský et al, 1993;Mok, 1994;Cherniad'ev, 2000;Synková et al, 2006). Furthermore, cytokinin influences photosynthesis and related processes (Kusnetsov et al, 1998;Synková et al, 1999;Yaronskaya et al, 2006;Cortleven and Valcke, 2012), which is at least partially due to the control of gene expression (Rashotte et al, 2003;Brenner et al, 2005;Zubo et al, 2005Zubo et al, , 2008.…”