Light control of shoot regeneration in callus cultures derived from barley (Hordeum vulgare L.) immature embryos

Abstract

Callus growth and shoot regeneration were examined in cultures of immature barley embryos incubated under various combinations of a week under a 16-h photoperiod and a week under continuous darkness. Incubation in darkness for four weeks, during which calli were formed, enhanced shoot regeneration in 'K-3' and 'Kanto Nijo-5', but inhibited it in 'Lenins'. 'K-3' and 'Kanto Nijo-5', incubated in darkness during the first two weeks of callus induction, followed by two weeks of a 16-h photoperiod (D2L2), showed a higher percentage of shoot regeneration than those incubated for two weeks with a 16-h photoperiod followed by two weeks of darkness (L2D2). Nevertheless, when the light conditions, D2L2 and L2D2, were combined into the same periods of a 16-h photoperiod and continuous darkness, except for the order, light conditions affected shoot regeneration differently. The early stage of callus induction seems to be sensitive to light. The expression ratios of the auxin-responsive gene (AUX/IAA) to the cytokinin-responsive gene (WPK4) were increased in continuous darkness in 'K-3' and 'Kanto Nijo-5'. The effects of light qualities (white, red, farred, and blue) on callus growth and shoot regeneration were also examined. Blue light inhibited shoot regeneration, as did white light, in 'K-3' and 'Kanto Nijo-5', and far-red light in 'Kanto Nijo-5'. Light probably controls shoot regeneration from calli by modifying cytokinin levels and/or response; blue light signals act in photo-inhibition of shoot regeneration in immature barley embryo culture.

Light Inhibition of Shoot Regeneration Is Regulated by Endogenous Abscisic Acid Level in Calli Derived from Immature Barley Embryos

“…Immature embryos (1–1.5 mm long) were excised aseptically. Modified MS medium with maltose (30 g l -1 ) was used as a basal medium [ 40 ]. The callus-induction medium was supplemented with 9 μM of 2,4-dichlorophenoxyacetic acid (2,4-D).…”

“…Genetic analysis shows that multiple genes in barley regulated shoot regeneration [ 37 , 38 ]. Shoot regeneration efficiency is in fact determined by physiological and environmental factors such as developmental stages of embryo, medium compositions and light conditions [ 39 , 40 ]. Light conditions during callus induction affect the shoot regeneration efficiency, although no effects are apparent in light conditions during shoot regeneration.…”

Barley (Hordeum vulgare L.) Improvement Past, Present and Future

“…However, several studies have been conducted to improve tissue culture techniques to increase regeneration rates [72]. From past to today, various tissue culture protocols have been developed by using immature embryos [73][74][75][76][77][78][79][80], mature embryos [81][82][83][84][85][86][87], apical meristems [88][89][90], anthers [91][92][93][94], microspores [95][96][97], ovaries [98,99], cell suspensions [100][101][102][103][104], protoplasts [105], coleoptile tissue [106] and leaf base segments [90,107].…”

Uzu, a barley semi-dwarf gene, suppresses plant regeneration in calli derived from immature embryos

“…Immature embryos and anthers were mainly used as explant sources in Communicated by H. Yamagishi Received November 26, 2007. Accepted February 26, 2008 barley tissue culture (Jähne et al 1991, Rikiishi et al 2008. Endogenous hormonal levels of explants and calli affected embryogenesis and plant regeneration in maize and wheat Bangerth 2001a, 2001b).…”