TELOMERES, TELOMERASE AND PLANT DEVELOPMENT

Telomeres are nucleoprotein structures that cap the ends of linear euk aryotic chromosomes. Almost all plant telomeres contain a characterist ic heptanucleotide, TTTAGGG, repeated in a tandem array that extends f or several kilobases. The length of the telomeric-DNA tract is dynamic , and subject to striking expansions and contractions that correlate w ith cellular differentiation. Telomeres are synthesized and maintained by the action of telomerase, a ribonucleoprotein with reverse transcr iptase activity. Telomerase expression profiles mirror changes in telo mere length, with the highest enzyme levels and telomere lengths assoc iated with cells that have unlimited capacity for proliferation. The e xcitement of current research using Arabidopsis is that it is the firs t opportunity for studying the regulation of telomeres and telomerase in a genetically tractable, multicellular organism.