Differential Expression of Gluconeogenesis-Related Transcripts in a Freshwater Zooplankton Model Organism Suggests a Role of the Cori Cycle in Hypoxia Tolerance

Abstract

Gluconeogenesis (GNG) is the process of regenerating glucose and NAD+ that allows continuing ATP 31 synthesis by glycolysis during fasting or in hypoxia. Recent data from C. elegans and crustaceans 32 challenged with hypoxia show differential and tissue-specific expression of GNG-specific genes. 33 2. Here we report differential expression of several GNG-specific genes in the head and body of a model 34 organism, Daphnia magna, a planktonic crustacean, in normoxic and acute hypoxic conditions. We predict 35 that GNG-specific transcripts will be enriched in the body, where most of the fat tissue is located, rather 36 than in the head, where the tissues critical for survival in hypoxia, the central nervous system and 37 locomotory muscles, are located. We measured the relative expression of GNG-specific transcripts in each 38 body part by qRT-PCR and normalized them by either the expression of a reference gene or the rate- 39 limiting glycolysis enzyme pyruvate kinase (PK).