Abstract
RNA-seq analysis was conducted to identify genes involved in adaptation to low-salinity conditions in two related Ulva species: U. prolifera restricted in brackish water (BW) and U. linza growing in seawater (SW). Samples of both organisms were cultured under either freshwater (FW), BW or SW, and their gene expression patterns were compared. The comparison between gene expression profiles of organisms cultured in FW and SW conditions identified 42 upregulated genes in U. prolifera and 139 in U. linza. Comparing organisms cultured in BW and SW conditions, 21 upregulated genes were identified in U. prolifera and 170 in U. linza. Moreover, the expression of 93 genes was downregulated in U. prolifera cultured in FW compared to SW and 51 genes in U. linza. In organisms cultured in BW compared to SW, 93 genes were downregulated in U. prolifera and 92 genes in U. linza. In both species, upregulated genes included genes functionally annotated as “ion transporters (DASS transporters),”and downregulated genes included genes annotated as“membrane”and“cell adhesion.”In U. prolifera, genes annotated “hydrolases (cell wall hydrolases)”were upregulated and those with“lipid metabolic process”were downregulated. Many genes annotated as“heat shock proteins”were upregulated in U. linza.
