Effects of temperature on muscle growth and collagen deposition in zebrafish (Danio rerio)

Collagen is a major extracellular matrix component playing pivotal roles in maintaining the muscle growth and flesh texture of fish. Enhancement of collagen deposition in muscle by environmental factors serves as an effective way to improve quality of fish products. However, as a critical environmental factor in aquaculture, the effects of temperature on muscle growth and collagen metabolism in fish are largely unknown. Here, we used zebrafish (Danio rerio) as a fish model to investigate the effects of water temperature (18 degrees C, 28 degrees C, 34 degrees C) on the growth performance, muscle structure and collagen metabolism. After the 7-week trial, the growth performance and density of muscle fiber were significantly reduced in 18 degrees C and 34 degrees C groups, compared to the control group (28 degrees C). While, the collagen deposition in muscle was significantly enhanced in low temperature group (18 degrees C). RNA-sequencing and qRT-PCR indicated that the transcription of collagen genes (col1a1a, col1a1b, col2a1b, etc.), genes regulating collagen synthesis (tgf-beta, ctgf) and degradation (mmp2, mmp9, timp2, etc.) were down-regulated as temperature increased. Furthermore, the protein processing in endoplasmic reticulum (ER) pathway was significantly affected by temperature. The transcription of molecular chaperones of procollagen (hsp47, p4hb, sec24a, etc) in the pathway was significantly up-regulated in high temperature group. Notably, no significant difference in the hydroxyproline content was observed among groups, suggesting a temperature compensation mechanism may exist during collagen post-translational modification (hydroxylation, etc.). It was concluded that temperature exerted profound effects on muscle growth and collagen metabolism in zebrafish. Appropriate low temperature was suggested to enhance collagen deposition in fish muscle during aquaculture practice. Our data would enrich basic knowledge of regulatory mechanism of collagen metabolism in fish and help to develop strategy for producing fish products with higher quality.