Nodular somatic embryogenesis and frond regeneration in duckweed,Lemna gibba G3 |
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Authors: | Heung-Kyu Moon Moon-Sik Yang |
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Institution: | (1) Biotechnology Division, Korea Forest Research Institute, 44-3, Suwon, 441-350 Kyonggido, Omokdong, Korea;(2) Division of Biological Sciences, Chonbuk National University, 664-14, Chonju, 561-756 Chonbuk, Dukjindong, Korea |
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Abstract: | Duckweed(Lemna gibba) is a useful model system for elucidating plant development, but the techniques needed for regenerating fronds from calli
are not yet well established. This study examined the effects of auxin, sucrose, and gelling agents on callus and frond formation
inL. gibba G3. After three weeks of culturing on a solid medium, two types of calli were observed: watery, pale-green, and undifferentiated;
or white, compact calli that were organized into nodules and which resembled somatic embryogenie calli. Homogeneous callus
lines were produced through selective subculture. To induce nodular calli, auxin (2,4-D) was absolutely required, with an
effective concentration of 5 to 20 μM; induction was found to be possible with up to a maximum concentration of 4.4%. The
calli were then maintained on a medium with a reduced 2,4-D concentration (1 μM), and were transferred every three weeks.
Optimal callus induction and growth were obtained by using 3% sucrose with a combination of 0.15% Gelrite and 0.4% agar. Fronds,
however, could be regenerated only on distilled water solidified with a combination of 0.4% agar and 0.15% Gelrite. On this
medium, 87% of the callus expiants regenerated into fronds after four weeks of culture. These new fronds were morphologically
normal but small, approximately 15 to 20% of the size of stock fronds. Continued culture of these fronds in an SH medium produced
normal duckweeds, and histological examination of the cultures revealed several distinct types of callus nodules. Nonetheless,
because zygotic embryogenesis inL. gibba does not produce distinct bipolar structures, the developmental pathway of frond regeneration from these nodular cultures
remains unknown. |
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Keywords: | Lemna gibba G3 regenerated fronds somatic embryogenic callus zygotic embryogenesis |
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