The effect of thermal stress on the X-organ/sinus gland proteome of the estuarine blue crab Callinectes sapidus during the intermolt and premolt stages

Abstract

Survival of brachyuran crabs is temperature-dependent and thermal stress promotes changes during molting. We aimed to decipher the impact of thermal stresses on the X-organ/sinus gland (XO/SG) complex, a temperature-sensitive neuroendocrine tissue involved in the molting regulation of Callinectes sapidus during the intermolt and premolt phases. We employed a proteogenomic approach using specimens subjected to control (24 °C), cold (19 °C), and heat (29 °C) temperatures. A total of 1463 protein groups with at least two unique peptides were identified and quantified. C. sapidus in the premolt stage exposed to the cold condition exhibited a proteome closely resembling that of the intermolt stage, as evidenced by measurements of circulating ecdysteroid levels. Compared to the intermolt at control temperature, the premolt stage exhibited increased energy metabolism, structural changes in the cuticle mediated by chitin metabolism and glycoproteins, biosynthesis of methyl farnesoate (MF), and elevated tissue levels of molt-inhibiting hormone (MIH) and crustacean hyperglycemic hormone (CHH), indicating lower secretion rates. Heat temperature (29 °C) seems to induce mitochondrial metabolism in the intermolt XO/SG, while cold temperature elicited a delayed molt cycle in the premolt phase, marked by reduced tissue levels of CHH, indicating increased secretion and Y-organ (YO) inhibition, and decreased MF production (reduced YO stimulation).

Significance statement

Temperature plays a pivotal role in regulating the metabolism, growth, molting, reproduction, and survival of crabs, such as the blue crab (Callinectes sapidus). Despite the blue crab's significance on both economic and ecological realms, there has been a notable lack of molecular information related to this species and therefore a gap in our knowledge of the blue crab's molecular makeup and genetic diversity. This research established a comprehensive proteome landscape to elucidate the molecular and functional changes in the XO/SG complex involved in the molting process of C. sapidus, and how thermal stresses significantly influence biotransformation processes. Utilizing a proteogenomics approach with multi-round homologous database analysis, we have generated a highly accurate protein repertoire with at least two unique peptide of XO/SG tissue proteome. This resource will be invaluable for future molecular analyses of this species. Our findings demonstrate that thermal stresses induced specific modifications in the XO/SG tissue, depending on the molt cycle phase. Temperature-mediated responses influences the biological processes, enhancing the functional morphogenesis and comprehensive metabolic adaptations on molting cycle supported by a relationship between the XO/SG tissue proteome and circulating ecdysteroid levels.