Vitamin D 5 in Arabidopsis thaliana.

Vitamin D ₃ is a secosterol hormone critical for bone growth and calcium homeostasis, produced in vertebrate skin by photolytic conversion of the cholesterol biosynthetic intermediate provitamin D ₃ . Insufficient levels of vitamin D ₃ especially in the case of low solar UV-B irradiation is often compensated by an intake of a dietary source of vitamin D ₃ of animal origin. Small amounts of vitamin D ₃ were described in a few plant species and considered as a peculiar feature of their phytochemical diversity. In this report we show the presence of vitamin D ₅ in the model plant Arabidopsis thaliana. This plant secosterol is a UV-B mediated derivative of provitamin D ₅ , the precursor of sitosterol. The present work will allow a further survey of vitamin D distribution in plant species.