An evaluation of gene expression during somatic embryogenesis of two temperature-sensitive carrot variants unable to complete embryo development |
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Authors: | Jennifer A Schnall Cheol H Hwang Todd J Cooke J Lynn Zimmerman |
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Institution: | Dept of Biology, Univ. of North Carolina, Chapel Hill, NC 27599–3280, USA;Univ. of Maryland, Dept of Botany, College Park, MD 20742, USA;Biological Sciences, Catonsville, MD 21228, USA. |
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Abstract: | The synthesis of putative stage-specific polypeptides during somatic embryogenesis of the carrot ( Daucus carota L. cv. Danvers) was investigated in the temperature-sensitive variants OB-2 and OB-3. These variants undergo normal embryo development to produce mature plantlets at the permissive temperature (24°C), but are arrested at the oblong stage to form elongated embryos without cotyledons at the restrictive temperature (33°C). Using two-dimensional polyacrylamide gel electrophoresis of in vivo labelled polypeptides, the patterns of stage-specific polypeptides in both lines were compared in: (1) oblong embryos grown at continuous 24°C vs oblong embryos exposed to 33°C during their temperature-sensitive period (i.e. embryos of identical morphology but different developmental fates); and (2) heartshaped embryos grown at constant 24°C vs enlarged oblong embryos exposed to 33°C during their temperature-sensitive period (i.e. embryos of the same age but different morphologies). The 22 putative stage-specific, polypeptides observed in this study fall into four classes: (1) line-specific, (2) age-specific, (3) unsynchronized, and (4) synchronized polypeptides. Only the last class, which consists of 4 polypeptides, exhibits synthesis patterns which are consistent with the polypeptides being causally involved in somatic embryo development. It is concluded that stage-specific behavior as assayed by PAGE analyses of simple 'present or absent' comparisons is insufficient to identify most of the polypeptides that may be relevant for somatic embryogenesis. |
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Keywords: | Carrot Daucus carota somatic embryogenesis stage-specific polypeptides temperature-sensitive variants |
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