Genetic and molecular analysis of tissue-culture-derived Ac elements

Area of Science:

• Plant genetics
• Molecular biology
• Maize (Zea mays L.) research

Background:

• Transposable elements, such as Activator (Ac), can exhibit genetic activity.
• Previous studies observed Ac activity in progeny of tissue-culture-derived maize plants, but not in progenitors.

Purpose of the Study:

• To investigate if Ac activity in tissue-culture-derived maize is linked to alterations in Ac-homologous DNA sequences.
• To identify structural changes in Ac DNA associated with its activation.

Main Methods:

• Generated maize families segregating for Ac activity via controlled crosses.
• Utilized a DNA probe from an Ac sequence to analyze Ac-homologous sequences in progeny and controls.
• Employed restriction fragment analysis (SstI, BglII) and methylation site analysis (PvuII, HpaII).

Main Results:

• All maize plants possessed six or more Ac-homologous DNA sequences, irrespective of Ac activity.
• Specific 30-kb (SstI) and 10-kb (BglII) Ac-homologous fragments cosegregated with Ac activity in one family.
• Hypomethylation at PvuII and HpaII sites was observed in active Ac sequences but was not consistently required for activity.

Conclusions:

• Tissue culture may activate previously silent Ac sequences in maize.
• Specific DNA fragments are associated with Ac activation, potentially representing the activated element.
• DNA hypomethylation might be a consequence, not a cause, of Ac activity in maize.