The Transcript-Level-Independent Activation of Ornithine Decarboxylase in Suspension-Cultured BY2 Cells Entering the Cell Cycle

Abstract

The regulation of ornithine decarboxylase (ODC) expression was studied in suspension-cultured tobacco (Nicotiana tabacum L.) BY2 cells. ODC activity increased rapidly 3 h after cells re-entered the cell cycle from the stationary phase, corresponding to the G1 phase, and continued to increase in the subsequent S phase, while the ODC transcript level increased only transiently. ODC activity was suppressed by sucrose-deficiency, while the ODC transcript level was not affected. U0126, a specific inhibitor of mammalian MAPK kinases (MEKs), significantly reduced ODC enzyme activity, but not the ODC transcript level. These results suggest that ODC activity is regulated independently of its transcript level in BY2 cells, and that sucrose and a U0126-sensitive protein kinase are required for the transcript-level-independent activation of ODC.

The role of polyamines during in vivo and in vitro development

“…Molecular aspects of polyaminemediated cell cycle progression have been established to a greater extent for mammalian systems (Oredsson 2003;Wallace et al 2003), although a number of parallels exists with cell cycle events in plants. Rapid ODC-dependent stimulation of polyamine biosynthesis occurs when stationary cells reenter the cycle at the G1 phase and elevated levels of spermidine and spermine coincide with the G1/S transition in both systems (Kwak and Lee 2002;Gemperlová et al 2005). Application of PA biosynthesis inhibitors is also sufficient to arrest the cell cycle .…”

“…Application of PA biosynthesis inhibitors is also sufficient to arrest the cell cycle . Polyamines further mediate the G2/M transition in plants, and the disparity observed between ODC and SAMDC transcripts and activities during the animal and plant cell cycles are indicative of transcriptional, translational, and posttranslational mechanisms of control being employed (Kwak and Lee, 2002;Coueé et al 2004). …”

Spermidine Is a Morphogenetic Determinant for Cell Fate Specification in the Male Gametophyte of the Water FernMarsilea vestita

“…Spermidine is a ubiquitous polyamine (Tabor and Tabor, 1984;Kaur-Sawhney et al, 2003) that is involved in a broad range of cellular processes in plants, fungi, and animals, such as cell division (Kwak and Lee, 2002;Ackermann et al, 2003;Unal et al, 2008), rapid cell growth and differentiation (Coueé et al, 2004;Imai et al, 2004), and transcription and translation Kashiwagi, 1999, 2000;Yatin, 2002;Covassin et al, 2003;Kaur-Sawhney et al, 2003;Baron and Stasolla, 2008). Intracellular levels of spermidine and other polyamines increase at specific stages of gamete development in the spermatogenous cells in a variety of animals, such as roosters (Gallus domesticus; Oliva et al, 1982), rats (Rattus norvegicus; Watts et al, 1987), sea star (Asterios forbesii; Sible et al, 1990), and humans (Homo sapiens; Quemener et al, 1992).…”

Stereo-Specific Transcript Regulation of the Polyamine Biosynthesis Genes by Enantiomers of Ornithine in Tobacco Cell Culture

“…Orn decarboxylation is known to be the main step in the PAs production. Transcription and enzyme activity of ODC are shown to be dominantly regulated in many processes of living cells (8-10). ODC is shown to be present in all living organisms and necessary for cell division, transcription process and growth under normal condition.…”