Degradation and release of dissolved environmental RNAs from zebrafish cells

Abstract

Environmental RNAs in water are gradually being applied in aquatic ecological surveys, water pollution monitoring, etc., but the current methods to detect environmental RNAs in water can mainly measure the RNAs in the filters that are used for filtering water samples, neglecting dissolved environmental RNAs in water. The sources and degradation profiles of dissolved environmental RNAs in water remain unknown. The present study was conducted to measure the permeability of extracted RNAs from zebrafish cells through filters, the degradation of extracted RNAs from zebrafish cells in tubes, and the release rate and degradation of dissolved environmental RNAs from living zebrafish cells and dying zebrafish cells, aiming to provide dynamic information from dissolved environmental RNAs in water. The results showed that there were no significant differences between the levels of extracted RNAs from zebrafish cells before filtration with 0.45 {micro}m filters and those in the filtrates. The extracted RNAs from zebrafish cells degraded in water in the tubes, and after 2 months, more than 15% of RNAs in the groups of RNAs in water were still detected. The half-life of all the RNAs in the tubes was approximately 20[~]43 days. During the 6-day experiment of the release and degradation of dissolved RNAs from living cells, an average of 4.1x10-4 [~] 1.7x10-3 pg dissolved RNAs (7.6x105 [~] 3.2x106 RNA bases) were secreted per cell per day into the liquid environment. During the 6-day experiment of the release and degradation of dissolved RNAs from dying cells, approximately 4.2 pg of dissolved RNAs released by a dying zebrafish cell in water could be detected. The dissolved environmental RNAs in water from zebrafish cells degraded faster in the presence of zebrafish cells: under the conditions without zebrafish cells, the average survival rate of the dissolved environmental RNAs in water per day was 98.4%/day; under the conditions with living zebrafish cells, the average survival rate per day was 49.7%/day; and under the conditions with dying zebrafish cells, the average survival rate per day was 34.9%/day. The estimated levels of dissolved environmental RNAs in water in fish tanks were too low to be detected by the current techniques. Although the methods in the present study need to be improved, this study may provide information to develop new ways to measure the dynamics of dissolved environmental RNAs in water and quantitatively analyze RNAs released into liquid environments of living and dying cells.