Effects of thermal stress on mortality and HSP90 expression levels in the noble scallops Chlamys nobilis with different total carotenoid content

Abstract

The noble scallop Chlamys nobilis is an economically important marine bivalve cultivated in the southern sea of China since the 1980s. Unfortunately, mass mortality of this scallop species often occurs in summer. The present study was conducted to investigate whether the expression of heat shock protein 90 (HSP90) and level of carotenoids could enhance high-temperature stress resistance in scallop. First, the HSP90 homolog of C. nobilis (designated CnHSP90) was identified and cloned. The complete cDNA sequence of CnHSP90 was 2631 bp, including a 2181-bp open reading frame (ORF) encoding a 726 amino acid polypeptide with five HSP90 family signatures, and sharing high homology with members of the HSP90 family. CnHSP90 was ubiquitously expressed in all examined tissues including the intestine, kidney, adductor, mantle, gill, and gonad, with the highest in the gonad. Golden and brown scallops, which contain significantly different total carotenoid content (TCC), were subjected to acute thermal challenge, and the LTE 50 (semi-lethal temperature at 36 h heat shock) and LTI 50 (semi-lethal time after heat shock) as well as the correlation between CnHSP90 gene expression and TCC were determined. The LTE 50 of golden scallop (32.14°C) was higher than that of brown scallops (31.19°C), with longer LTI 50 at all tested temperatures, indicating that golden scallops were more resistant to thermal stress than brown scallops. Similarly, the mRNA expression levels of CnHSP90 in gill of golden scallops were significantly higher (P < 0.05) than that of brown scallops at 6, 12, 24, and 36 h, with a strong positive correlation between CnHSP90 expression level and TCC. This suggests that both carotenoids and HSP90 levels could improve thermal resistance in the noble scallops.

Roles of Carotenoids in Invertebrate Immunology

“…Altered environmental conditions can directly affect immunity by changing the concentration and efficiency of cytokine receptors, cytokines, and cells of the immune response, or indirectly affecting immunity by inducing general stress responses (128). Carotenoids have increased the resistance of invertebrates to environmental stress factors such as low salinity (46) and heat stress (26,38,45,97). Under low salinity stress, the SOD content and expression level of scallop serine protease inhibitor (SPI) gene were positively correlated with total carotenoids, indicating that carotenoids enhanced the resistance of C. nobilis to low salinity (46).…”

Characterization of a novel catalase gene and its response to low temperature stress in noble scallop Chlamys nobilis with different total carotenoids content

“…For example, CAT can stimulate or mediate innate immune gene response in crustaceans and molluscs after viral or bacterial infections (Arockiaraj et al, 2012;Wang et al, 2013). Though several studies have shown that the physiological and immune processes of aquatic animals would be disturbed under high temperature stress (Cheng et al, 2020;Malev et al, 2010;Tu et al, 2012;Yu et al, 2017;Zhu et al, 2016), the effects of low temperature stress on physiological and immune processes in molluscs are still unclear.…”

Identification and Characterization of HSP90 Gene Family Reveals Involvement of HSP90, GRP94 and Not TRAP1 in Heat Stress Response in Chlamys farreri

“…Peng et al [70] report that, during heat stress, the expression of HSP70 and HSP90 increase gradually to maximum levels, at 28℃, in Huso dauricus. In C. nobilis [30], Laternula elliptica [71], Argopecten irradians [41], and Sitodiplosis mosellana [16], the expression of HSP90 significantly increases during the thermal stress period. In our study, the expressions of CfHSP90 and CfGRP94 were significantly up-regulated in the mantle, gill, and blood under heat stress.…”

“…Unlike HSP90α, HSP90β lacks the glutamine-rich sequence (QTQDQ) at its N-terminus [27]. In invertebrates, only one form of HSP90 protein has been reported [28][29][30]. However, GRP94 and TRAP1 are found in both vertebrates and invertebrates [31].…”