Light Requirement for Shoot Regeneration in Horseradish Hairy Roots

Abstract

Hairy roots of horseradish (Armoracia rusticana) were induced by inoculation with Agrobacterium rhizogenes harboring Ri plasmid and cultured on phytohormone-free Murashige and Skoog medium after eliminating the bacteria. Hairy roots grew vigorously and sometimes formed yellowish calli under dark conditions. On the other hand, growth of hairy roots stopped after several weeks of culture with light, then shoots were regenerated. Frequency of shoot formation from hairy roots increased as the culture period in light lengthened and the light intensity increased. The shoot regeneration was induced by treatment with white or red light, but not with far-red light. Shoot regeneration by red light was inhibited by following treatment with far-red light. Red and far-red light reversibly affected shoot regeneration. Excised roots of nontransformed plants grew quite slowly on phytohormone-free Murashige and Skoog medium and occasionally formed shoots under white light conditions. ment for shoot formation in both hairy roots and excised roots of nontransformed plants of horseradish. MATERIALS AND METHODS Induction and Maintenance of Hairy RootsHairy roots were obtained by inoculating sterilized leaves of horseradish (Armoracia rusticana) with Agrobacterium rhizogenes strain 15834 harboring Ri plasmid (pRi 15834). Several weeks after the inoculation, tip segments of hairy roots that appeared on the inoculated sites were cut off and cultured on hormone-free MS2 semi-solidified (0.2% gerlite) medium containing an antibiotic (Claforan, 500 mg/L) at 250C under dark conditions. Segments of growing hairy roots were transferred several times to the fresh MS medium to eliminate the bacteria and then transferred to hormone-free MS medium without antibiotics.

Action spectrum for light-induced formation of adventitious shoots in hairy roots of horseradish

“…Correspondence to: T. Saitou; FAX: 81(298)536006 this promotive effect of red light was reduced when it was followed by irradiation with far-red light (Saitou et al 1992), indicating that phytochrome is probably involved in light-induced formation of adventitious buds in hairy roots of horseradish.…”

“…After infection of plants with A. rhizogenes, the T-DNA is integrated into the plant genomic DNA and its genes induce the formation of hairy roots (Chilton et al 1982;Tepfer 1984;Zambryski et al 1989) Adventitious bud formation in hairy roots of some plant species can be induced by light (Noda et al 1987;Petit et al 1987;Saitou et al 1991Saitou et al , 1992. In Lotus corniculatus, shoots formed spontaneously on hairy roots without any phytohormone treatments when the roots were cultured in the light (Petit et al 1987).…”

Plant regeneration: cellular origins and molecular mechanisms

“…A well-documented environmental condition that influences plant regeneration is the exposure to light, but its impact on regeneration appears to be highly context dependent. Light is required for shoot regeneration in some plant species (Reuveni and Evenor, 2007) and can also trigger organ regeneration (Saitou et al, 1992;Sorin et al, 2006;Gutierrez et al, 2009). On the other hand, exposure to light can have an inhibitory effect on root or shoot regeneration in some contexts (Bellini et al, 2014;Nameth et al, 2013).…”

Accumulation of a Clock-Regulated Transcript during Flower-Inductive Darkness in Pharbitis nil1

“…102, Mitsubishi Rayon Co., Ltd., Tokyo, Japan) that excluded light at wavelengths below 600 nm (Saitou et al, 1992). FR light (0.8 W m Ϫ2 ) was obtained from a lamp (model FL20S-FR74, Toshiba Electronics Co., Tokyo, Japan) with a passage filter (Saitou et al, 1992). The cotyledons and other organs were excised, frozen in liquid nitrogen, and stored at Ϫ80°C.…”

“…Red light (0.6 W m Ϫ2 ) was obtained by passage of the abovementioned fluorescent light through a sheet of red acrylic resin (Acrylite no. 102, Mitsubishi Rayon Co., Ltd., Tokyo, Japan) that excluded light at wavelengths below 600 nm (Saitou et al, 1992). FR light (0.8 W m Ϫ2 ) was obtained from a lamp (model FL20S-FR74, Toshiba Electronics Co., Tokyo, Japan) with a passage filter (Saitou et al, 1992).…”