Cycloheximide resistance in carrot culture: a differentiated function.

Area of Science:

• Plant biology
• Cellular differentiation
• Molecular biology

Background:

• Cultured carrot cells (Daucus carota) form unorganized callus in auxin-containing media.
• Auxin removal induces organized growth and embryo differentiation from callus.
• Cycloheximide inhibits normal callus growth (W001C) but not embryonic growth.

Purpose of the Study:

• To investigate the mechanism of cycloheximide resistance in carrot cell cultures.
• To identify the role of cycloheximide inactivation in differentiated versus undifferentiated tissues.

Main Methods:

• Isolation and characterization of a cycloheximide-resistant variant cell line (WCH105).
• Analysis of cycloheximide inactivation in callus and embryos of both wild-type and variant lines.
• Comparison of growth responses to auxin and bromodeoxyuridine.

Main Results:

• WCH105 callus exhibited resistance to cycloheximide inhibition, unlike W001C callus.
• Cycloheximide inactivation was identified as the mechanism for resistance in WCH105 callus and embryos of both lines.
• Bromodeoxyuridine promoted callus growth similarly to auxin.
• Cycloheximide inactivation was present in differentiated tissues (embryos, plantlets) but absent in undifferentiated callus.

Conclusions:

• Cycloheximide inactivation is a key mechanism conferring resistance in differentiated carrot tissues.
• This suggests that the capacity for cycloheximide inactivation is acquired during cellular differentiation.