An Assessment of Possible Factors Contributing to Recalcitrance of Plant Protoplasts

The Complexity of Enzymic Control of Hydrogen Peroxide Concentration May Affect the Regeneration Potential of Plant Protoplasts

“…The isolation of protoplasts from leaf mesophyll results in an alteration of cell metabolism; an increase of toxic forms of oxygen has been detected, which has been suggested to be the cause of poor protoplast regeneration (Roubelakis-Angelakis, 1993). Toxic oxygen stimulates lipid peroxidation in cultured tissues Roubelakis-Angelakis, 1993, 1994) and directly inhibits many enzymes; for instance, 10 p~ H,O, is inhibitory for some enzymes involved in the photosynthetic CO, fixation (Kaiser, 1976) and 50 p~ H,O, is inhibitory for the cytoplasmic enzyme aconitase (Verniquet et al, 1991).…”

“…The complex metabolic modifications that protoplasts undergo during their isolation may include an alteration in the oxygen balance, with an overproduction of active forms of oxygen, namely superoxide anion, H,O,, and hydroxyl radical (Roubelakis-Angelakis, 1993). Toxic oxygen may affect the morphogenic response of cells and other plant explants Roubelakis-Angelakis, 1993, 1994) and its increasing accumulation after protoplast isolation has been indicated as a cause of recalcitrance (Siminis et al, 1994).…”

Catalase Is Differentially Expressed in Dividing and Nondividing Protoplasts

“…Among the factors assessed that may contribute to recalcitrance of protoplasts is oxidative stress (Ishii, 1988;Cutler et al, 1989;Roubelakis-Angelakis, 1993). Wounding, cell wall hydrolytic enzymes, and change of cultured protoplasts and cells from autotrophic to heterotrophic metabolism in the presence of altered hormonal status are some of the factors that induce oxidative stress.…”

“…the inability to express regenerating potential at the leve1 of either cell division or morphogenesis in vitro. The process(es) and mechanism(s) inducing the onset of the undifferentiated meristematic state in cultured protoplasts are very poorly understood (Roubelakis-Angelakis, 1993). It has been estab-* Corresponding author; fax 30-81-233669.…”

Pathways of ROS homeostasis regulation in Mesembryanthemum crystallinum L. calli exhibiting differences in rhizogenesis

“…It has already been demonstrated that oxidative stress is involved in regeneration and morphogenic processes in in vitro culture (Kapur et al 1993;Roubelakis-Angelakis 1993;Papadakis et al 2001;Konieczny et al 2008;Macedo et al 2009;Kalra and Babbar 2010;Abbasi et al 2011;Petřivalský et al 2011). Oxidative stress results from an imbalance between ROS generation and the antioxidant capacity of cells.…”