Abstract
Heat shock proteins (Hsps) are highly conserved molecular chaperones that are synthesized in response to stress. In this study, we cloned the full-length sequences of the Grp78 (glucose-regulated protein 78), Hsp70, Hsp90, and Hsp40 genes from the Chinese rice grasshopper Oxya chinensis. The full-length cDNA sequences of OcGrp78, OcHsp70, OcHsp90, and OcHsp40 contain open reading frames of 1947, 1920, 2172, and 1042 bp that encode proteins of 649, 640, 724, and 347 amino acids, respectively. Fluorescent real-time quantitative PCR (RT-qPCR) was performed to quantify the relative transcript levels of these Hsp genes in different tissues and developmental stages. The mRNAs encoding these four Hsp genes were present at all developmental stages and in all tissues examined but were expressed at varying levels. Additionally, we investigated the mRNA expression profiles of these four Hsps in O. chinensis subjected to Cadmium (Cd) stress. OcGrp78, OcHsp70, OcHsp90, and OcHsp40 mRNA expression was induced under acute Cd stress; the levels reached a maximum within a short time (6 h), were reduced significantly at 12 h, and were lowered to or below control levels by 48 h. Regarding induction efficiency, OcHsp70 was the most sensitive gene to acute Cd stress. Chronic Cd exposure showed that dietary Cd treatment induced increased OcGrp78, OcHsp90, and OcHsp40 expression. However, dietary Cd induced a significant reduction of OcHsp70 expression. In the period tested, no significant difference in the mortality of the grasshoppers was observed. Our results suggest that these four Hsps genes, especially OcHsp70, are sensitive to acute Cd stress and could be used as molecular markers for toxicology studies. However, our results also indicate that OcHsp70 is not suitable for use as a molecular marker of chronic Cd contamination.
Highlights
Heat shock proteins (Hsps), or stress proteins, are a group of conserved proteins that are synthesized by organisms upon exposure to environmental stressors, including heat shock, radiation, pesticides, metal, and other environmental contaminants
OcHsp40 expression increased to 2.0-fold that of the control until 24 h, followed by a decrease at 48 h. These results show that OcHsp70, OcGrp78, and OcHsp90 mRNA levels are highest after 6 h of exposure to 2.7 mgÁkg-1 Cd
The typical characteristics of Hsp70 family members were observed in the deduced amino acid sequences of OcHsp70 and OcGrp78
Summary
Heat shock proteins (Hsps), or stress proteins, are a group of conserved proteins that are synthesized by organisms upon exposure to environmental stressors, including heat shock, radiation, pesticides, metal, and other environmental contaminants. Hsps play an essential role by assisting in the correct folding of proteins to maintain cellular homoeostasis under stress conditions [1,2]. Hsp gene expression is widely accepted as a suitable molecular indicator of adverse biological effects because Hsps respond to minor environmental stress and are evolutionarily conserved [5,6]. Much of the research on cellular responses to metals and other pollutants has focused on Hsps, especially Hsp because of its high conservation and sensitivity to stress factors [6,7,8,9,10]
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