DEVELOPMENT PATTERNS OF TELOMERASE ACTIVITY IN BARLEY AND MAIZE

Eukaryotic chromosomes terminate with specialized structures called te lomeres. Maintenance of chromosomal ends in most eukaryotes studied to date requires a specialized enzyme, telomerase. Telomerase has been s hown to be developmentally regulated in man and a few other multicellu lar organisms, while it is constitutively expressed in unicellular euk aryotes. Recently, we demonstrated telomerase activity in plant extrac ts using the PCR-based TRAP (Telomeric Repeat Amplification Protocol) assay developed for human cells. Here we report telomerase activities in two grass species, barley and maize, using a modified, semi-quantit ative TRAP assay. Telomerase was highly active in very young immature embryos and gradually declined during embryo development. The endosper m telomerase activity was detectable, but significantly lower than in the embryo and declined during kernel development with no detectable a ctivity in later stages. Telomerase activity in dissected maize embryo axis was several orders of magnitude higher than in the scutellum. Te lomerase activity was not detected in a range of differentiated tissue s including those with active meristems such as root tips as well as t he internode and leaf base. The role of telomerase repression during d ifferentiation and the relationship between chromosome healing and tel omerase activity is discussed.