Rapid cold-hardening: Ecological significance and underlying mechanisms

Abstract

Introduction Insects are constantly subjected to changes in environmental temperature. Most studies of insect acclimation to low temperature concern seasonal changes that occur over weeks or months in preparation for winter, and, accordingly, most chapters in this volume focus on seasonal cold-hardening. In contrast, during the past 10 years considerable attention has been paid to rapid acclimatory responses to both high (i.e. induction of heat shock or stress proteins (Feder et al. , 2002) and low temperature. This chapter summarizes our current understanding of the rapid cold-hardening (RCH) response. When our previous book (Lee and Denlinger, 1991) was being written, the RCH response had only just been described and merited only a few scattered paragraphs. Indeed, at that time it was unclear whether this response was merely a laboratory artifact or a previously unrecognized type of rapid acclimation. Since then, the RCH response has emerged as a highly conserved trait, allowing diverse insect groups to swiftly adjust their physiological state and organismal performance to match even modest changes in environmental temperature. In this chapter, we summarize evidence supporting the ecological relevance and emerging physiological underpinnings of the RCH response. The RCH response protects against a form of non-freezing injury known as cold-shock or direct-chilling injury. Cold-shock injury is well known among microbes, plants and animals, and represents a major obstacle for the successful cryopreservation of many types of cells and tissues (Grout, 1987). Injury is not associated with internal ice formation.