Physiological control of germline development

Abstract

The intersection between developmental programs and environmental conditions that alter physiology is a growing area of research interest. The C. elegans germ line is emerging as a particularly sensitive and powerful model for these studies. The germ line is subject to environmentally regulated diapause points that allow worms to withstand harsh conditions both prior to and after reproduction commences. It also responds to more subtle changes in physiological conditions. Recent studies demonstrate that different aspects of germ line development are sensitive to environmental and physiological changes and that conserved signaling pathways such as the AMPK, Insulin/IGF, TGFβ, and TOR-S6K, and nuclear hormone receptor pathways mediate this sensitivity. Some of these pathways genetically interact with but appear distinct from previously characterized mechanisms of germline cell fate control such as Notch signaling. Here, we review several aspects of hermaphrodite germline development in the context of "feasting," "food-limited," and "fasting" conditions. We also consider connections between lifespan, metabolism and the germ line, and we comment on special considerations for examining germline development under altered environmental and physiological conditions. Finally, we summarize the major outstanding questions in the field.

Fig. 5.1

The C. elegans lifecycle, diapause, and germline development. Figure adapted from (Wood et al. 1980) and modified from (Korta and Hubbard 2010). Time (hours at 25°), hatching and molts are indicated. Physiologically sensitive diapause and larval germline expansion are indicated. Circular arrow indicates renewal potential of adult germ cells

Fig. 5.2

Signaling for developmental and germline response to poor conditions by PI3K, TGFβ, AMPK, and S6K pathways. See text for details and references