Cellular responses to environmental salinity in the halophilic black yeast Hortaea werneckii

Summary The development of crop plants with increased salt tolerance necessitates the study of naturally salt- tolerant eukaryotic species. We studied the bio- synthesis of glycerol as a compatible solute in the halophilic eukaryotic microorganism, black yeast Hortaea werneckii. A restriction fragment-differential display technique was used to investigate the tran- scriptome of the organism. Eight differentially expressed genes were identified in response to growth at different salinities. Although the putative functions of their products, P-type ATPase, ubiquinone reductase, aconitase, RNA helicase, Asn-tRNA ligase, isoamyl alcohol oxidase, and phosphatidylinositol-3-kinase, are not intimately related within the cellular machinery, the results pre- sented here are sufficient to propose a model which describes how H. werneckii adapts to extremely high salinities. Some of these mechanisms of adaptation to raised environmental salinity are similar to those in other salt-sensitive species, e.g. glycerol accumu- lation, there also appear to be novel mechanisms present such as the use of different energy produc- tion mechanisms and post-transcriptional regulation of gene expression. Our results have also provided new data on two genes from two other fungal species, the Neurospora crassa B1D1.130 gene and the Aspergillus ustus amdS-A gene.