Transcriptome profiles of Daphnia magna across to the different water chemistry of surface water of the Korean Demilitarized Zone

Abstract

The Korean Demilitarized Zone (DMZ) has almost completely protected surface water conditions. Despite the water conditions of DMZ are excellent clear, downstream of river or natural irrigation ponds near the region are recently developed by human activities such as agriculture, ginseng fields or ecotourism. To understand the potential effect of physico-chemical characteristics of the DMZ water, the freshwater model Daphnia magna was exposed to water samples that were collected from four sites near the DMZ. RNA-seq identified some differentially expressed transcripts which are sensitive to small differences of water chemistry. Particularly transcripts coding for the stress responsive heat shock protein (Hsp) superfamily and innate immune system were significantly increased in response to the water samples of irrigation ponds and downstream of Seweol river where are analyzed to have low pH and high levels of chemical fertilizer nutrients such as nitrogen (N) and phosphorus (P). These water samples decreased mRNA expressions of crucial members which are involved in crustacean morphogenesis and reproduction metabolism (e.g. cuticle protein family, ecdysteroid metabolism, vitellogenesis). Evidence on the high transcriptional sensitivity of the aquatic model D. magna against small differences of water chemistry will be a useful strength for further applications in environmental and ecotoxicological genomics.