Arabidopsis ETHE1 encodes a sulfur dioxygenase that is essential for embryo and endosperm development

Mutations in human (Homo sapiens) ETHYLMALONIC ENCEPHALOPATHY PROTEIN1 (ETHE1) result in the complex metabolic disease ethylmalonic encephalopathy, which is characterized in part by brain lesions, lactic acidemia, excretion of ethylmalonic acid, and ultimately death. ETHE1-like genes are found in a wide range of organisms; however, the biochemical and physiological role(s) of ETHE1 have not been examined outside the context of ethylmalonic encephalopathy. In this study we characterized Arabidopsis (Arabidopsis thaliana) ETHE1 and determined the effect of an ETHE1 loss-of-function mutation to investigate the role(s) of ETHE1 in plants. Arabidopsis ETHE1 is localized in the mitochondrion and exhibits sulfur dioxygenase activity. Seeds homozygous for a DNA insertion in ETHE1 exhibit alterations in endosperm development that are accompanied by a delay in embryo development followed by embryo arrest by early heart stage. Strong ETHE1 labeling was observed in the peripheral and chalazal endosperm of wild-type seeds prior to cellularization. Therefore, ETHE1 appears to play an essential role in regulating sulfide levels in seeds.