Morphoregulatory Role of Thidiazuron

Abstract

Somatic embryogenesis was induced in hypocotyl explants of geranium (Pelargonium x hortorum) cultured on media supplemented with various concentrations of N-phenyl-N'-1,2,3-thiadiazol-5-ylurea (thidiazuron). In less than 2 weeks, somatic embryos were observed in treatments containing levels of thidiazuron (TDZ) ranging from 0.2 to 1.0 micromolar. The use of N'-benzylaminopurine in combination with indole-3-acetic acid also evoked embryogenesis, but the efficiency of somatic embryo production was significantly lower than that obtained with TDZ. Hypocotyl culture for only 2 days on TDZ-supplemented medium before transfer to a basal medium was sufficient for inducing somatic embryogenesis. This distinction between the induction and expression of embryogenesis may provide an experimental system for studying the developmental biology of somatic embryogenesis. Substitution of the auxin-cytokinin requirement for the induction of somatic embryogenesis by TDZ suggests the possibility of a novel mode of its action by modulation of endogenous growth regulators.TDZ3, a substituted phenylurea (N-phenyl-N'-1,2,3-thiadiazol-5-ylurea; Dropp), is primarily used as a cotton defoliant (1) and has been shown in various cytokinin bioassays to exhibit strong cytokinin-like activity similar to that of N6-substituted adenine derivatives (12). In many cytokinin-dependent callus cultures, the application of TDZ evoked a comparable or higher degree of growth response than adenine-based cytokinins (5, 20). The morphogenetic responses in which TDZ has been found to mimic cytokinin-like activity include release of lateral buds from dormancy (21) and shoot formation in cultures of a wide variety of plant species (7,9 cytokinins, or it may induce the synthesis and (or) accumulation of endogenous cytokinins (5, 11). The latter notion is based on the effects of the high ability of TDZ in inducing cytokinin-dependent shoot regeneration and modulation of endogenous levels of cytokinins. In this communication, we demonstrate the high efficiency of TDZ in stimulating somatic embryogenesis in geranium hypocotyl cultures, a response usually mediated by an appropriate combination of an auxin and a cytokinin. Our results suggest for the first time that auxin(s) may also be involved in the induction and/or expression of TDZ-induced morphogenic differentiation. MATERIALS AND METHODSSeeds of the diploid zonal geranium (Pelargonium x hortorum Bailey) cv Scarlet Orbit Improved were surface sterilized by dipping in 95% ethanol for 30 s and then immersing in a 1.2% solution of sodium hypochlorite containing two drops of Tween 20 per 200 mL. Seeds were agitated in this solution for 20 min and then rinsed three times in sterile distilled water. Ten seeds were aseptically cultured per 100 x 15 mm Petri dish on 30 mL of MS (13)

TDZ-Induced High Frequency Plant Regeneration through Direct Shoot Organogenesis in <i>Stevia rebaudiana</i> Bertoni: An Important Medicinal Plant and a Natural Sweetener

“…The regenerants induced from lower levels of TDZ developed roots sooner and grew faster than those obtained from higher concentrations. TDZ can subsititute both the auxin and cytokinin requirement and contribute to different modes of morphogenetic responses as organogenesis and somatic embryogenesis as reported by several authors [27][28][29]. The rooted plants exhibited 95% survival rate 8 weeks after transfer to the soil.…”

Development of an efficient protocol for high-frequency regeneration system in Hibiscus syriacus L.

“…Although TDZ is classified as a type of cytokinin, it is chemically very different from the auxins and cytokinins that are generally used to induce callus and shoot formation, and exerts both auxin-and cytokinin-like effects (Guo et al 2011). Previous studies have shown that TDZ is much more effective than any other cytokinin for inducing the production of multiple shoots (Bates et al 1992;Fellman et al 1987;Neuman et al 1988;Visser et al 1992). However, several studies reported that although TDZ induced shoot growth, it did not support continuous shoot elongation (Yoo et al 1996).…”

ESTABLECIMIENTO DEL SISTEMA DE REGENERACION POR EMBRIOGÉNESIS SOMÁTICA DE Azadirachta indica A. Juss.

“…Así Visser et al, (1992) señalan en secciones de hipocótilo de Pelargonium, que la acción exógena de citocininas como el TDZ potencia la síntesis y subsecuente acción del mejor balance de auxinas/citocininas a nivel endógeno, que favorezca de manera óptima la inducción de la embriogénesis somática. Asimismo, en el cultivo líquido de callo de Coffea arabica sometidos a pulsos (24-48 horas) de BAP, se induce significativamente la diferenciación de embriones somáticos, debido a las propiedades de este regulador de crecimiento a minimizar la liberación de especies reactivas de oxigeno (ROS) que son altamente toxicas al proceso morfogénico como lo es la embriogénesis somática, ya que éstas están relacionadas a la activación de mecanismos apostóticos celulares, esto también ha sido reportado en caña de azúcar por Medeiros De Araújo Silva et al, (2014).…”