– BST1 overexpression conferred resistance to sphingosine in yeast. BST1 deletion produced sensitivity to exogenous D-erythro-sphingosine and phytosphingosine and intracellular accumulation of sphingosine 1-phosphate upon exposure to exogenous sphingosine. sphingoid base metabolism is similar in all eukaryotes and suggests that yeast genetics may be useful in the isolation and identification of other genes involved in sphingolipid signaling and metabolism.