Chi Gek Lan
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Publication Role of ethylene on de novo shoot regeneration from cotyledonary explants of brassica campestris ssp. pekinensis (Lour) olsson in vitro(1991) Chi, G.-L.; Pua, E.-C.; Goh, C.-J.; BOTANY; INSTITUTE OF MOLECULAR & CELL BIOLOGYThe promotive effect of AgNO3 and aminoethoxyvinylglycine (AVG) on in vitro shoot regeneration from cotyledons of Brassica campestris ssp. pekinensis in relation to endogenous 1-amino-cyclopropane-1-carboxylic acid (ACC) synthase, ACC, and ethylene production was investigated. AgNO3 enhanced ACC synthase activity and ACC accumulation, which reached a maximum after 3 to 7 days of culture. ACC accumulation was concomitant with increased emanation of ethylene which peaked after 14 days. In contrast, AVG was inhibitory to endogenous ACC synthase activity and reduced ACC and ethylene production. The promotive effect of AVG on shoot regeneration was reversed by 2-chloroethylphosphonic acid at 50 micromolar or higher concentrations, whereas expiants grown on AgNO3 medium were less affected by 2-chloroethylphosphonic acid. The distinctive effect of AgNO3 and AVG on endogenous ACC synthase, ACC, and ethylene production and its possible mechanisms are discussed.Publication Synergistic effect of ethylene inhibitors and putrescine on shoot regeneration from hypocotyl explants of Chinese radish (Raphanus sativus L. var. longipinnatus Bailey) in vitro(1996) Pua, E.-C.; Sim, G.-E.; Chi, G.-L.; Kong, L.-F.; BOTANY; INSTITUTE OF MOLECULAR & CELL BIOLOGYThe role of ethylene and putrescine on shoot regeneration from hypocotyl explants of Chinese radish (Raphanus sativus L. var. longipinnatus Bailey cv. Red Coat) was investigated. Explants were recalcitrant in culture, but exogenous application of ethylene inhibitor 120-30 μM aminoethoxyvinylglycine (AVG) or AgNO3] enhanced shoot regeneration of explants grown on medium supplemented with 2 mg/l N6-benzyladenine and 1 mg/l 1-naphthaleneacetic acid. The best regeneration occurred in the medium containing AgNO3 in combination with AVG. Culture medium solidified with agarose in the presence of AgNO3 but not AVG was also beneficial to shoot regeneration. Exogenous putrescine, 2-chloroethylphosphonic acid and 1- aminocyclopropane 1-carboxylate had no effect on shoot regeneration. However, regeneration was greatly promoted by 10-25 mM putrescine in combination with 30 μM AgNO3 or AVG. Explants with high regenerability grown in the presence of AgNO3 or in combination with putrescine emanated high levels of ethylene throughout the 21-d culture period. By contrast, AVG or putrescine alone resulted in a decrease in ethylene production. For rooting of shoot cuttings, IAA and IBA at 1-5 mg/l were more effective than NAA.Publication Role of polyamines on de novo shoot morphogenesis from cotyledons of Brassica campestris ssp. pekinensis (Lour) Olsson in vitro(1994-03) Chi, G.-L.; Lin, W.-S.; Lee, J.E.E.; Pua, E.-C.; BOTANY; INSTITUTE OF MOLECULAR & CELL BIOLOGYThe promotive effect of ethylene inhibitors (Els), i.e. AgNO3 and aminoethoxyvinylglycine (AVG) on de novo shoot regeneration from cultured cotyledonary explants of Brassica campestris ssp. pekinensis cv. Shantung in relation to polyamines (PAs) was investigated. The endogenous levels of free putrescine and spermidine in the explant decreased sharply after 1-3 days of culture, whereas endogenous spermine increased, irrespective of the absence or presence of Els. AgNO3 at 30 μM did not affect endogenous PAs during two weeks of culture. In contrast, explants grown on medium containing 5 μM AVG produced higher levels of free putrescine and spermine which increased rapidly after three days and reached a peak at 10 days. An exogenous application of 5 mM putrescine also resulted in a similar surge of endogenous free spermine of the explant. More strikingly, shoot regeneration from explants grown in the presence of 1-20 mM putrescine, 0.1-2.5 mM spermidine, or 0.1-1 mM spermine was enhanced after three weeks of culture. However, exogenous PAs generally did not affect ethylene production, and endogenous levels of 1-aminocyclopropane-1-carboxylate (ACC) synthase activity and ACC of the explant. This study shows the PA requirement for shoot regeneration from cotyledons of B. campestris ssp. pekinensis in vitro, and also indicates that the promotive effect of PAs on regeneration may not be due to an inhibition of ethylene biosynthesis. © 1994 Springer-Verlag.Publication Effect of AgNO3 and aminoethoxyvinylglycine on in vitro shoot and root organogenesis from seedling explants of recalcitrant Brassica genotypes(1990-08) Chi, G.-L.; Barfield, D.G.; Sim, G.-E.; Pua, E.-C.; INSTITUTE OF MOLECULAR & CELL BIOLOGYThe presence of 1-10 μM aminoethoxyvinylglycine (AVG) or 5-30 μM AgNO3 markedly enhanced shoot regeneration from cotyledon and hypocotyl cultures of eight recalcitrant Brassica campestris and B. juncea genotypes tested. Expiants of B. campestris ssp. chinensis and ssp. parachinensis grown with a high AVG concentration (20 μM), regenerated poorly. All cytokinins tested were equally effective in promoting shoot formation, except that kinetin was inhibitory to shoot regeneration from hypocotyls of B. campestris ssp. pekinensis (cv. Wong Bok). Both AgNO3 and AVG had no effect on percent rooting and number of roots per rooted cutting of Wong Bok, White Sun and Leaf Heading, but AgNO3 was inhibitory to rooting of India Mustard. However, root elongation of all cuttings was markedly inhibited by AVG at concentrations of 5 and 10 μM. © 1990 Springer-Verlag.Publication Ethylene inhibitors enhanced de novo shoot regeneration from cotyledons of Brassica campestris ssp. chinensis (Chinese cabbage) in vitro(1989) Chi, G.-L.; Pua, E.-C.; INSTITUTE OF MOLECULAR & CELL BIOLOGYA tissue culture system for obtaining high frequency shoot regeneration of Brassica campestris ssp. chinensis cv. Speedy and 2B-21-64 was optimized via judicious selection of explants and manipulation of culture medium with respect to hormonal combination and addition of AgNO3, Ag2SO4, aminoethyoxyvinylglycine (AVG), aminooxyacetic acid (AOA) or 2,4-dinitrophenol (DNP). Three-day-old cotyledons of both cultivars grown on Murashige and Skoog's medium supplemented with 4.4-17.6 μM benzyladenine and 2.7-5.4 μM naphthaleneacetic acid (NAA) in the presence of 7.5-60 μM AgNO3 or Ag2SO4 or medium containing 8.8 μM BA, 5.4 μM NAA and 0.1-10 μM AVG formed shoots at 70-85% frequency after 3-4 weeks, whereas explants grown in the absence of Ag+ or AVG or in the presence of AOA or DNP were poorly regenerative (20-30%). Shoot tips originating from regenerants and seedlings rooted equally well in hormone-free medium or medium containing 0.05-5 μM indolebutyric acid. All rooted shoots were successfully acclimatized. The acclimatized plants were phenotypically indistinguishable from those derived from seeds. © 1989.