Endogenous biological rhythms and clocks in Antarctic krill
Alfred Wegener Institute for Polar and Marine Research (AWI), Australian Antarctic Division (AAD), University of Padova (UP), Charité Universitätsmedizin Berlin (CUB)
This work package will focus on how important seasonal physiological changes in krill will be mediated by environmental cues via endogenous timing systems (e.g. circadian/circannual) during the ontogeny of krill. The Meyer lab at the AWI has developed a comprehensive krill data set, covering all seasons, on biochemical composition, growth and metabolic activity at organismic, cellular and molecular levels. In addition, this group generated a high-quality normalized cDNA library, obtained from total RNA extracted from different krill tissues sampled in the Antarctic natural environment at different seasons, which has been subsequently pyrosequenced. In close collaboration with the Costa lab (see WP2), the total “454-generated” reads will be used to generate a new version of the krill microarray platform (krill 1.2), which will constitute the most updated representation of the Antarctic krill transcriptome. This platform will allow the analysis of more than 35,000 transcripts at the same time. Using the krill 1.2 platform, the gene expression signature of transcripts specifically involved in important physiological traits throughout the photoperiodic cycle will be studied in a) adult krill, maintained under a simulated seasonal course of photoperiod in the krill aquarium at the AAD (mimicking 66° South where krill is currently particularly abundant), and b) during krill’s ontogeny from the first larval to one year adult stage, which will be reared from eggs at the AAD under simulated Antarctic light condition. Moreover, we will investigate the putative role of the krill’s circadian clock in seasonal time-keeping and in the control of seasonal physiological state changes in the life-cycle of krill. Therefore, transcript levels of canonical clock genes (see WP2) in correlation with key physiological target genes will be analyzed around the circadian cycle under different light:dark (LD) conditions throughout the simulated seasonal course of photoperiod. To collect evidence for the effects of latitudinal migration, manipulative photoperiodic studies (e.g. phase advance and delay experiments) will be performed to identify differential gene expression as a consequence of photoperiod. Photoperiod aside, the effects of other environmental cues on endogenous physiological rhythms and the accompanied endogenous clock machinery in krill will be tested. The group at the AAD will prepare krill at various life stages by both raising eggs as well as bringing animals back from the field through regular Antarctic cruises to maintain them throughout annual cycles across multiple generations in the aquarium, under various simulated environmental conditions (e.g. temperature, light, food quality and quantity, CO2). This allows the team to pursue periodic physiological measurements and tissue samplings for molecular analysis by Meyer and Costa groups to test krill’s responses to climate change in physiological functions and gene activity via gene expression, as well as how both are related to each other.