Immune system of aquatic organisms can be affected by long-term ecological alterations? Focusing on Prophenoloxidase (proPO) and NLHS-induced proPO gene expression of Artemia Urmiana

Abstract Recent ecological changes in Urmia Lake may affect immune system of local organisms, including Artemia urmiana, prompting the need to study immune regulation mechanisms in species being able to cope with stressors, survive, and reproduce under these conditions. This study evaluated effects of long-term environmental changes on the prophenoloxidase (proPO) expression as a key immune response and non-lethal heat shock (NLHS)-induced proPO expression in this species. qPCR assay was developed to evaluate the influence of three-decade ecological crisis on proPO and NLHS-induced proPO expression of nauplii of Artemia urmiana, based on cyst collections from 1994 (rainy period) to 2020 (drought period). To obtain partial cds of proPO, four regions of this cDNA were sequenced using Sanger method. Before expression analysis, four regions of proPO cDNA were sequenced (the accession numbers: OQ784234, OQ784235, OQ784236, OQ784237) and then assembled into a larger partial cds (the accession numbers: OQ784174). qPCR results demonstrated that ecological changes caused proPO expression shifting, which was highest in 2005 (CI 95%, p < 0.001). Notably, the nauplii exposed to longer-term changes were able to increase proPO expression more than others in response to NLHS (CI 95%, p < 0.001). Our findings highlighted effects of ecological stressors on proPO and NLHS-induced proPO expression. Notably, prior exposure to stressors may confer survival and adaptation advantages against future challenges, indicating a bright side of long-term environmental stressors.