Dicarbonyl/L-xylulose reductase (DCXR) producing xylitol regulates egg retention through osmolality control in .

To support life, the osmolality of the cellular fluid is tightly regulated by various means, including osmolyte control. Dicarbonyl/L-xylulose reductase (DCXR) is a highly conserved enzyme reducing L-xylulose to xylitol, which serves as an effective osmolyte in various mammalian and human tissues such as lung epithelium, sperm, and lens. DHS-21 is the only DCXR ortholog in , and DCXR null mutant worms accumulate eggs in the uterus. However, it has been unknown how and why the mutant worms impair egg retention. In this study, we tested whether the egg-retention in ), the DCXR null mutant worm is sensitive to changes in osmolarity. Low osmolality reverted the egg retention phenotype of , while high osmolarity aggravated it. Also, knock-down of either one of , or , osmoregulatory genes, also rescued egg-retention phenotypes of the null mutants. The study indicates that DCXR functions in fluid homeostasis by regulating cellular osmolality in and provides insights into DCXR-involved clinical conditions, such as congenital cataracts and malfunctioning lung and kidney.