A new IL6 isoform in Chinese soft-shelled turtle (Pelodiscus sinesis) discovered: Its regulation during cold stress and infection

Abstract

The Chinese soft-shelled turtle (<i>Pelodiscus sinesis</i>) is a widely cultured commercial species in East and Southeast Asian countries. The turtles frequently suffer from acute cold stress during farming in China. Stress-induced factor such as Interleukin-6 (IL6) is a multifunctional molecule that plays important roles in innate and adaptive immune response. In the present study, we found that the turtle possessed two IL6 transcripts, where one IL6 transcript contained a signal peptide sequence (<i>psIL6</i>), while the other IL6 transcript (<i>psIL6ns</i>) possessed no such signal peptide gene. To test any differential expression of the two isoforms during temperature and microbial stress, turtles were adapted to optimal environmental water temperature (25 °C), stressed by acute cooling for 24 h, followed with the challenge of <i>Aeromonas hydrophila</i> (1.8 × 10⁸ CFU) or <i>Staphylococcus aureus</i> (5.8 × 10⁸ CFU). Gene characterization revealed that <i>psIL6ns</i>, a splicer without codons encoding a signal peptide and identical to the one predicted from genomic sequence, and <i>psIL6</i>, a splicer with codons encoding a signal peptide, were both present. Inducible expression was documented in primary spleen cells stimulated with ConA and poly I: C. The splenic and intestinal expression of <i>psIL6ns</i> and <i>psIL6</i> was increased in response to temperature stress and bacterial infection.