Heat Shock Protein 40 (HSP40) in Pacific White Shrimp (): Molecular Cloning, Tissue Distribution and Ontogeny, Response to Temperature, Acidity/Alkalinity and Salinity Stresses, and Potential Role in Ovarian Development.

Heat shock proteins (HSPs), a family of conserved proteins that are produced by cells in response to stresses, are known as molecular chaperones with a range of housekeeping and cellular protective functions. The 40 kD heat shock protein (HSP40) is a co-chaperone for HSP70 in the regulation of ATP hydrolysis. Unlike its well-documented cofactor HSP70, little is currently known regarding the biological functions of HSP40 in crustacean species such as penaeid shrimp. In the present study, the cDNA encoding HSP40 (-HSP40) was identified from the Pacific white shrimp , a highly significant commercial culture species. The structural organization indicates that Lv-HSP40 belongs to the type-I HSP40s. The muscle, gill, and hepatopancreas are the main sites of transcript expression. Within these tissues, mRNA were predominantly exhibited in the myocytes, epithelial cells and hepatopancreatic cells, respectively. Under acute thermal stress in the culture environment, transcript levels are significantly induced in these three tissues, while low pH stress only upregulates mRNA in the hepatopancreas and gill. During ontogenesis, transcript levels are high at early embryonic stages and drop sharply at late embryonic and early larval stages. The ovary is another major organ of mRNA expression in female shrimp, and transcripts were mainly presented in the follicle cells but only weekly detected in the oocytes. Ovarian mRNA levels increase continuously during gonadal development. Silencing of the gene by RNA interference may effectively delay ovarian maturation after unilateral eyestalk ablation. The roles of Lv-HSP40 in ovarian development are speculated to be independent of its cofactor HSP70, and the vitellogenesis factor vitellogenin () and vitellogenin receptor (). Our study, as a whole, provides new insights into the roles of HSP40 in multiple physiological processes in : (1) HSP40 is a responding factor during stressful conditions; and (2) HSP40 participates in embryonic and ovarian development.