Aging-Specific Expression ofDrosophila hsp22

Abstract

hsp22is among the least abundantly expressedDrosophilaheat shock (hs) genes during both development and heat stress. In contrast,hsp22was found to be the most abundantly expressed hs gene duringDrosophilaaging. During aging,hsp22RNA was induced 60-fold in the head, with somewhat lower level induction in abdomen and thorax. Induction of the other hs gene RNAs was ≤3-fold, except forhsp23,which was induced ∼5-fold in thorax. hsp22 protein was detected using rat anti-hsp22 polyclonal antisera and was induced >150-fold, with particularly abundant expression in eye tissue. Aging-specific induction ofhsp22was reproduced byhsp22:lacZfusion reporter constructs in transgenic flies. Analysis of specific promoter mutations in transgenic flies indicated that functional heat shock response elements are required forhsp22induction during aging. Finally, comparison ofhsp22RNA and protein expression patterns suggests that aging-specific expression ofhsp22is regulated at both the transcriptional and the posttranscriptional levels. Aging-specific induction ofhsp22is discussed with regard to current evolutionary theories of aging.