Telomeres and telomerase: active but complex players in life-history decisions.

Studies on human telomeres have established that telomeres exert a significant influence on lifespan and health of organisms. However, recent research has indicated that the original idea that telomeres affect lifespan in a universal and central manner across all eukaryotic species is an oversimplification. Indeed, findings from a variety of animal species revealed that the role of telomere biology in aging is more subtle and intricate than previously recognized. Here, we show how telomere biology varies depending on the taxon. We also show how telomere biology corresponds to basic life history traits and affects the life table of a species and investments in growth, body size, reproduction, and lifespan; telomeres are hypothesized to shape evolutionary perspectives for species in an active but complex manner. Our evaluation is based on telomere biology data from many examples from throughout the animal kingdom that vary according to the degree of organismal complexity and life history strategies.

Seasonal changes in ultrastructure and gene expression in the fat body of worker honey bees.

The anatomical, physiological, and behavioral characteristics of honey bees are affected by the season as well as division of labor. In this study, we examined the structure, ultrastructure, and gene expression of fat body cells in both long-lived winter and short-lived summer worker bees (the youngest stage of hive bees and forager bees). In contrast to hive bees, foragers and winter bees have a higher metabolism due to intensive muscle activity during their flight (foragers) or endothermic heat production (winter bees). These workers differ from hive bees in the biology of their mitochondria, peroxisomes, and lysosomes as well as in the expression of the genes involved in lipid, carbohydrate, amino acid metabolism, insulin, and TGF- ß signaling. Additionally, the expression of genes related to phospholipid metabolism was higher in the hive bees. However, we found no differences between workers in the expression of genes controlling cell organelles, such as the Golgi apparatus, endoplasmic reticulum, ribosomes, nucleus, and vacuoles, as well as genes for DNA replication, cell cycle control, and autophagy. Furthermore, lysosomes, autophagic processes and lipofuscin particles were more frequently observed in winter bees using electron microscopy.

Seasonality in telomerase activity in relation to cell size, DNA replication, and nutrients in the fat body of Apis mellifera.

In honeybees (Apis mellifera), the rate of aging is modulated through social interactions and according to caste differentiation and the seasonal (winter/summer) generation of workers. Winter generation workers, which hatch at the end of summer, have remarkably extended lifespans as an adaptation to the cold season when the resources required for the growth and reproduction of colonies are limited and the bees need to maintain the colony until the next spring. In contrast, the summer bees only live for several weeks. To better understand the lifespan differences between summer and winter bees, we studied the fat bodies of honeybee workers and identified several parameters that fluctuate in a season-dependent manner. In agreement with the assumption that winter workers possess greater fat body mass, our data showed gradual increases in fat body mass, the size of the fat body cells, and Vg production as the winter season proceeded, as well as contrasting gradual decreases in these parameters in the summer season. The differences in the fat bodies between winter and summer bees are accompanied by respective increases and decreases in telomerase activity and DNA replication in the fat bodies. These data show that although the fat bodies of winter bees differ significantly from those of summer bees, these differences are not a priori set when bees hatch at the end of summer or in early autumn but instead gradually evolve over the course of the season, depending on environmental factors.

Telomerase activity is upregulated in the fat bodies of pre-diapause bumblebee queens (Bombus terrestris).

The attrition of telomeres, the ends of eukaryote chromosomes, and activity of telomerase, the enzyme that restores telomere length, play a role in the ageing process and act as indicators of biological age. A notable feature of advanced eusocial insects is the longevity of reproductive individuals (queens and kings) compared to those from non-reproductive castes (workers and soldiers) within a given species, with a proposed link towards upregulation of telomerase activity in the somatic tissues of reproductive individuals. Given this, eusocial insects provide excellent model systems for research into ageing. We tested telomerase activity and measured telomere length in Bombus terrestris, which is a primitively eusocial insect species with several distinct features compared to advanced social insects. In somatic tissues, telomerase activity was upregulated only in the fat bodies of pre-diapause queens, and this upregulation was linked to heightened DNA synthesis. Telomere length was shorter in old queens compared to that in younger queens or workers. We speculate that (1) the upregulation of telomerase activity, together with DNA synthesis, is the essential step for intensifying metabolic activity in the fat body to build up a sufficient energy reserve prior to diapause, and that (2) the lifespan differences between B. terrestris workers and queens are related to the long diapause period of the queen. A possible relationship between telomere length regulation and TOR, FOXO, and InR as cell signaling components, was tested.